Vray for Rhino - Tutorials

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GettingStarted < VfR < TWiki http://www.asgvis.com/VfRtw/bin/view/VfR/GettingStarted?template=... 1 de 2 28/09/2006 17:02 Getting Started Set up a Scene Start off by creating a simple scene with a few objects. A cylinder, cone, and sphere are good objects to start with, and make sure to put a plane underneath them. Next we want to give the objects a simple material, so give each of the objects a different color just to see some variation between them. Setting Renderer Now that we have a scene created we need to set VRay as the renderer. In order to set VRay as your render engine go to Render > Current Renderer and select VRayForRhino. Setting GI To start a GI rendering, open the VRay Render Options (go to VRay > Options). The first setting is in the Indirect Illumination rollout: Check the box underneath GI to enable it. Then go to the Global Switches

Transcript of Vray for Rhino - Tutorials

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Getting Started

Set up a Scene

Start off by creating a simple scene with a few objects. A cylinder, cone, and sphere are good objects tostart with, and make sure to put a plane underneath them. Next we want to give the objects a simplematerial, so give each of the objects a different color just to see some variation between them.

Setting Renderer Now that we have a scene created we need to set VRay as the renderer. In order to set VRay as yourrender engine go to Render > Current Renderer and select VRayForRhino.

Setting GI

To start a GI rendering, open the VRay Render Options (go to VRay > Options). The first setting is in theIndirect Illumination rollout: Check the box underneath GI to enable it. Then go to the Global Switches

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rollout and under Lighting uncheck Default Lights. Then go to the Environment rollout, check GI and Background and change the GI color to White. Next go to the Output rollout and check Override Rhino.For now, click 640x480 or set up something smaller. Click Render.

Adjustments

Here is the rendered image on the right. These are the basic initial steps of setting up VRay. From herethere are many adjustments that can be made within the render options of VRay as well as setting up materials and lighting in order to achieve the desired effect of your rendering.

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Setting up Vray for Large Resolution Rendering Summary From time to time we are asked to produce images at a very high resolution. In V-Ray for Rhino, this ispossible when writing to the VrImage file format (found in the RenderOptions > Output section). This optionwrites the image to disk during the rendering process.

Introduction There is a three step process to render large resolution images. Step one is to have V-Ray calculate a V-Ray Irradiance Map or VrMap ? file of only half the resolution of the final image with low irradiance map settings. In some cases you can get away with calculating even less then half of the final resolution needed. The next step is to use the calculated map to render the final image resolution. Finally you'll needto convert the VrImage file format into OpenEXR ? format to be able to open it in Photoshop or other image editing software. Please note that rendering a large resolution image is both big in file size and RAMexpensive. So be sure that you have around 2-3 GB of disk space and about 1GB of RAM free.

Step One:

Open the scene you wish to render.Go to RenderOptions > GlobalOptions ? rollout and enable "Don't render final image".Go to RenderOptions > Output section and enable "override rhino" and set your resolution to half of your desired final resolution.Under the Irradiance map rollout enable the "New Map mode" and "Autosave" feature. Choose afilename and location that you will remember.Now render the VrMap ? file

Step Two:

With the scene you wish to render still open, go to RenderOptions > GlobalOptions ? rollout and disable "Don't render final image".Go to RenderOptions > Output section and set the resolution to the desired final resolution.Enable "Render to VrImage" and choose a filename and location that you will remember.Under the "Irradiance map" rollout enable the "From File mode" and locate the VrMap ? file you saved in the first step.Now render the final file.

Step Three:

Convert the VrImage using the VrimgtoExr converter.

Resources See CommonToolsDownload OpenEXR PhotoShop plugin

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History: r5 - 15 Jul 2006 - 01:19:56 - BrianPerry

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Depth of Field (DOF) Summary One of the best render effects to add more photorealism to a scene is "Depth of Field". Like a photo from areal camera, objects in the rendering will be in focus at the set distance away from the camera. Objects closer or farther away appear progressively unfocused as they move away from the focal point. The effect can be very subtle or very strong. The importance of the effect is that it mimics what the human eye sees. Images of small objects tend to show more DOF han images of large objects. In the real world, the cameralens length determines the DOF intensity. Wide angle lenses show less DOF than telephoto lenses.

Introduction

The DOF effect is enabled by checking the Render Options > Camera > Depth of Field box. If the option Override focal Dist. is disabled, the focal point will be the Rhino3D camera target. The camera target can be shown by right-clicking the viewport name, and selecting show camera. To set the focal distance independant of the camera target, enable the Override focal Dist. option.

DOF control options:

Rhino3D camera target placed at the focal point:

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No DOF enabled:

DOF enabled with aperture 4:

DOF enabled with aperture 16:

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Aperture - this is the size of the virtual camera aperture in world units. Small aperture sizes reduce the DOF effect (less blur) and larger sizes increase it (more blur). So an aperture of 4 units can be both 4 mm or 4 m depending on the Rhino3D model units. The example images (3) .. (5) are shown usingcentimeters.

The option subdivs can be used to control the noise in the DOF sampling. If full adaptive mode is used, the subdivs option is ignored.

Bokeh effects

Bokeh effects are special DOF effects of lenses. This kind of lens blurring is different than a standard gaussian blur used in photo editing software. It can show the sides of the aperture or the effects of the lenssystem. More information about bokeh can be found at Wikipedia.

Test scene: Three textured HDRI emitter planes:

aperture 4 - Center 0 - Sides 5 - Classic bokeh effect:

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aperture 4 - Center 1 - Sides no - A typical mirror telephoto lens ring effect:

aperture 4 - Center 0.1 - Sides 5 - Aniso 0.6 - An stretched effect similar to a panoramic cinema movie lenses:

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Example of a Bokeh effect of a classic Nikon 50 mm lens:

Detailed information about the DOF options can be found at the Vray online help page.

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Decal Materials Keywords Decal mapping, Mapped transparency

Material creation

The goal is to create a sphere with a carbon material and a decal applied to it.

Rendered scene with materials (left) and Rhino3d viewport (right):

First we setup two mapping channels, the first is set to use "spherical" projection and the second is set to "planar" (example image below). The projection widget can be manipulated by enabling the show mapping option. (The widget is the white rectangle in the above image.)

Mapping type control using Rhino3D RCM tool:

The material based on two diffuse layers. The layers of the material editor are in order of the calculation. The light goes from the upper layers to the lower layers. In this example the first layer is the decal. Image (3) show the layers and the maps. The first layer is set at full transparency with white color.

Decal material and maps:

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By disabling the tile option on the transparency map layer the transparency texture will not be tiled and will be used just once. The surface around the decal texture is controlled by the transparency color. In this example white becomes transparent. Image (4) shows the transparency control with the texure in decal mode. Attention: the map channel is set at channel 2 (planar projection - see above). The transparency map is a black&white map. If a normal alpha texture is used with a white object and black background, the invert option helps to get the right effect.

Texture dialog of the transparency layer:

The same settings are used for the second diffuse layer. The only difference is that the color map is used instead. Not shown here is a clear finish coat that is added using an additional reflection layer with fresnelenabled .

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Main basic settings

This tutorial uses the following settings:

Image sampler - Adaptive QMC 0/50 QMC sampler - adaptive amount 1 + noise threshold 0.05 + min samples 8 + subdiv mult 1 Color mapping - Reinhard + multiplier 1 + burn 0.2 + clamp output + affect background Indirect Illumination - "on" + no caustics + primary engine QMC + secondary engine light cache Light cache - subdivs 600 + sample size 0.02 + num phases 1 + adaptive disable

The LC and QMC GI modes help to create nice consistant images without any attention to setting lots of options. The "Reinhard" color mapping helps the burn option to keep the brightest areas of the image. TheQMC settings are used to set Vray in full adaptive mode. In this mode, the noise quality is controlled by only one option - the noise threshhold.

The advantage of the GI LC pass is that it produces a fast preview of the scene very quickly and is used tohelp the user answer basic questions like: Is the lighting right? Are all objects at in right place? Are the materials assigned correctly? This raw physical lighting sample of the whole scene is calculated first and allfollowing passes are based on it.

Scene setup

A typical interior architecture scene is shown in Image 1: a room inside a hotel. A large rectangular light with of intensity (30) and ignore light normals enabled is used to simulate the light from outside. The direct light source in the window provides a clean and fast GI calculation. If an HDRI environment is used, than a rectangular light in light portal mode helps to combine the advantages of the colored HDRI light and the direct light. The cylindrical lamps are emitter materials with intensity 5. There is no glass in the windows.

Image 1: Hotel scene

The spot light at the entrance area is really three different lights: a Rhino spot light (inverse square decay and intensity 90,000), a rectangular light (intensity 200 and invisible) and an emitter disk (intensity 30). This special spot combination has these advantages:

Spotlight - Light cone covers a limited area near the ground.Invisible rectangular light - simulates the soft light near the walls around the spotlight.Emitter disk - simplest visible model for a round down light hanging from the ceiling.

r7 - 27 Sep 2006 - 22:11:36 - MichaelMehnert

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Why is the arealight not used without the emitter disk? A small emitter in a much bigger room produceslots of noise and/or longer calculation time. Why not a rectangular light without the extra emitter? Rectangular lights are rectangular and downlights are round. ;o)

Image 2: Special Spot: Combination of spotlight, rectangular light, and disk shaped emitter:

The current version of Vray for Rhino does not support objects that are invisible to the camera only. If a wall is replaced like in the scene, the indirect light distributation is disordered which results in light being lost in the infinite space around the scene. A slight compensation using the GI environment light set at intensity 0.5 and a light warm color (255,229,204 - captures the mood of the light in the room) can help. The environment light simulates the indirect light reflecting off walls that were removed. Image (3) shows the scene with GI environment and Image (4) without the GI environment.

Image 3: Preview (screenshot after LC pass) without GI environment:

Image 4: Final image:

UPDATE: it is possible to hide objects from the scene like ceiling or walls and to keep the GI lighting. An

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easy trick must be done: the scene must be rendered in passes. First must be calculated GI cache files with all objects in the scene. Than, objects can be hidden and the final calculation can be started - based on the previous GI caches. Here step by step:

Create a special material for the "look through" objects with transparency value (10,10,10). So, the camera can look inside the room and the lighting will be calculated inside.Set GI primary engine LC and secondary IM.Set cache paths for both engines and enable autosave.Enable "don't render final image" for Indirect Illumination at the Global switch options. (is not a must)Start rendering.After the rendering is finished, disable cache "autosave" and enable "from file". The cache path can be copied and pasted from the save option to read option.Hide all objects that are not needed in the image.Disable "don't render final image".Render the final image.

Extra trick: if the LC option "use for glossy rays" is used, than the hidden object will be visible in glossyrefelctions.

Image (5) show an example: the front wall and the ceiling is removed for the second pass. No additional environment light is used, only the window rectangular light and the three emitter cylinder lights. The spot lights from the previous images are removed for the test, so that the GI effect is better visible.

Image 5: Scene in "hidden object" technic:

At the end of the page can be find the scene for experiments, all materials are easy working without textures now.

UPDATE: An easier way to get a "for the camera hidden wall" is to set the wall or ceiling at transparency color value 10. If no light come from outside, the wall is invisible for the camera. The frame buffer exposurecontrol helps to get the right brightness of the image. If a GI environment is be used, than an additional black box (simple Rhino material) around camera and wall/ceiling as light catcher is necessary. Here an example of a simple textured scene: some spot are place inside the room, arealight in portal mode are placed in the windows and the GI environment is set to a HDRI. The sphere in the middle of the room showthe complete scene with ceiling.

Hidden ceiling per leight transparent ceiling material:

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... under construction by Micha

Main basic settings

The tutorial base on the following settings:

Image sampler - Adaptive QMC 0/50 QMC sampler - adaptive amount 1 + noise threshold 0.05 + min samples 8 + subdiv mult 1 Color mapping - Reinhard + multiplier 1 + burn 0.5 + clamp output + affect background Indirect Illumination - "on" + no caustics + primary engine QMC + secondary engine light cache Light cache - subdivs 600 + sample size 0.02 + num phases 1 + adaptive disable

The LC and QMC GI modes help to create nice consistant images without any attention to setting lots of options. The "Reinhard" color mapping helps the burn option to keep the brightest areas of the image. The QMC settings are used to set Vray in full adaptive mode. In this mode, the noise quality is controlled by onlyone option - the noise threshhold.

The advantage of the GI LC pass is that it produces a fast preview of the scene very quickly and is used to help the user answer basic questions like: Is the lighting right? Are all objects at in right place? Are the materials assigned correctly? This raw physical lighting sample of the whole scene is calculated first and all following passes are based on it.

Scene setup

An architectural scene is shown in Image 1: A model of a house is placed in a simple surroundings. The goal is to show the model with natural lighting: Diffuse lighting from the sky and the sun. The simplest method is to set a blue environment color/background and distant light (for the sun). A more advanced method isto use a texture map as the environment. Using a high contrast HDRI (i.e., something with a bright sun) is not recommended. This causes a slow and noisy GI calculation. A better method is to use a low contrast environment map of the sky (Shown in Image 2) and an additional distant light source for the sun.

Image 1: Rhino3D Architecture scene:

Image 2: Environment map:

As a start, we set the environment at intensity 14 (Image 2) and render the scene without anylight from the top view (Image 4). After seeing the lighting of the environment, we can if necessary correct the alignment of the environment by manipulating the environment settings or editing the texture in image editing software. We then add a yellowish distant light (i.e., RGB 255,218,180) so that it matches the lighting of the environment map.

The advantage of a single color environment instead of a texture map is that the "mood" of the color can be changed much easier and no alignment of sun light source and texture is needed.

Image 3: Environment setting for map used in Image 2:

r11 - 15 Jul 2006 - 05:57:52 - BrianPerry

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Image 4: Top view of the scene without and with additional sun light (screnshot LC pass):

Image 5 shows the first test render - the background is too dark and can be adjusted using the environment option. The ground around the house is to blue because the blue environment is stronger than the sun intensity. In reality, the blue light is seen only in the shadows of the sun. New sun intensity is 2 and to avoid a burn out of the whole image, the GI environment intensity is decreased to 8. Image 6.

Image 5 First test: GI Environment intensity 14 + backgound 14 + distant light 1:

Image 6 Final raw image (noise threshhold 0.01):

Post work

It is often easier to adjust the mood of an image using some post work instead of manipulating the rendering parameters. A vingnetting effect increases the realism of the image and can be added easily during postwork using a free Photoshop plugin PTLens. I often use an additional warm look. Example options

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show Image 7 with less blue and more red.

Image 7: Warm mood color correction using Photoshop:

Image 8: Final image:

Materials Important: Caustics need a lot of calculation power and are not necessary for architecture visualization. The simplest glass is a single surface object with a single reflection layer in fresnel mode. If colored glass is needed, than an additional refraction layer with a refraction color must be set. The affect shadowoption must also be enabled so that the material acts as transparent material with shadows that are the color of the refraction color. If the refraction IOR is set to1, the object can be a single surface object.

Image 9: Flat glass material good for architecture visualization:

Very important: materials and colors should not be brighter than color value 200 - approx. 80% reflectance (the maximum real world reflectance of white colored objects). If the brightness of a color is too high, too much indirect light will be reflected, the lighting could look wrong, and the image can be dull. A good way to control colors are the HSV values (Rhino3D color chooser). For example, the V value of the wall color is 150 only - a medium grey.

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Render speed optimization

The usage of full adaptive sampling mode helps to avoid the setting of material based subdivs. Only one general noise threshhold parameter controls the quality of the image. The same for the primary GI engine - the QMC GI mode is controlled by the adaptive sampling.

The noise threshhold should be set at 0.01 or 0.005 for very little noise. But for high resolution images a higher noise level is often good enough, the small amount of "grain" is sometimes seen in photos as well.

Image 10 Higher resolution and higher noise threshhold 0.02:

If more speed and less noise is needed, changing the secondary engine doesn't help much because the LC mode is very good and quite fast. The primary engine can be changed at Irradiance Mode, but for small details you must be careful usin the IM settings. Here is a download for an animated GIF with three IMtests in comparison to the QMC GI. As you can see, low IM settings destroy the details of the lighting.

GI_test_animation.gif (800k)

The best solution is to use the IM at very high settings: min/max -1/1 and 128 samples. Image 11 shows the result. Image 11: Rendered per GI LC+IM and noise threshhold 0.02:

Rhino mesh settings

My favorite mesh settings are shown in Image 12. The mesh is controlled by the single parameter Maximum distance, edge to surface. For architecture renderings, simple planes, is very useful ".

Image 12: Rhino3D mesh controls:

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Studio Setup for Product and Industrial Design Key words Scene setup - light setup - material setup - GI setup - camera setup - color mapping "Reinhard"

General Scene settings

This tutorial will not cover the setup for studio lighting itself because this topic is covered very well by books about rendering and photography. A very useful book for render engine independent rendering topics like studio lighting can be found here http://www.3drender.com/.

This tutorial is based on a simple scene with two light colored rectangular lights with opposite colors. Try to to avoid pure white lights. As an alternative, use a white light and additional colored lights. A scene with colored lights will look less CG like. Also, the most physically correct solution is to use rectangular lights and disable the options: no decay and ignore light normals. The advantage of rectangular lights are: shadows, lighting, and reflections of the lightsource match perfectly.

Image 1: Studio scene with two rectangular lights:

A basic rule for physically correct materials is to avoid pure black (RGB 0,0,0) and white (RGB 255,255,255). For renderings without Global Illumination (GI), it does not matter which white value is used. In GI mode, if the white is set at (0,0,0), too much diffuse light will be reflected and will cause an incorrect indirect lighting effect. In the real world, the maximum diffuse reflection is approximately 80%, and 80% of 255 = 204. A value of 200 is good standard value for the brightest white surfaces. This rule is especially important for interior renderings.

The same rule for textures applies. But there is a problem in that most textures use a color space from RGB 0 ... 255. An easy correction is to use the blend multiplier. The material color must be set to (0,0,0) and the texture multiplier to 0.8. If the material color is set above (0,0,0), than the black value of the texture will be higher.

Image 7 below shows an example: Using the bright wood texture without correction would cause too much

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light to bounce between the wooden ribs. In a previous test with bright birch wood, a strong glowing effect between the ribs was visible.

Image 2: Texture brightness correction:

The easiest way to control the quality of a rendering is to use the full adapative sampling mode Image 3. The user does not need to control the subdivs options of the lights and material. Instead, the quality is globally controlled by one parameter - the noise threshhold. For a quick preview, a threshhold of 0.05 is useful (for even less noise try 0.005). It is recommended to set the automatic subdiv range from 0 ... 100, but I often use 0 ... 50 or 0 ... 20 only. A max rate 100 is good for many cases, but the rendering may be slower.

Image 3: Full adaptive sampling:

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Image 4: First raw preview:

The current Rhino3D rendered viewport does not show all mapping modes, therefore a quick test rendering is necessary. An easy way to render an image for texture control is to add the output of the diffuse channel in the VFB Channels option. If all lights are disabled in the Global switches section and GI is turned off, the rendering is very fast. The output channel can be found at the frame buffer. See Image 5.

Image 5: Additional output channel at the frame buffer:

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An additional Depth of Field (DOF) effect increases the realism that can be enabled on the Vray Cameraoptions page. The focal length is set by the Rhino3D camera target (RMB on the viewport name -> show camera). Note: if the DOF effect is too strong, the objects in focus may look very small.

Image 6: Additional DOF effect - Arperture 0.5:

Global Illumination using LC and QMC

The easiest method of controlling GI is the combination of the secondary engine Light Cache (LC) and primary engine Quasi-Monte Carlo GI (QMC GI). This method is not the fastest, but is very stable and flexible. It keeps the details of lighting simple and the user does not need many controls: only noise threshold and LC subdivs are required. An extra advantage is that the LC pass produces a quick preview of the whole scene. If the Num. Phases of the LC options is set to 1, the LC pass is not divided in sub-passes and the quality of the LC pass can be estimated. If more phases are set, less memory is used, but the user can not estimate the quality of the LC pass.

The LC pass calculates physically correct lighting for the whole scene and is used as base for the primary GI engine. The QMC GI do not need to be changed and the bounce control is inactive for the primary engine. An important parameter is the subdivs of LC. If the LC does not converge to an image with less black noise, than the subdivs should be increased - (i.e., for interior renderings at 1200 or more).

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In my opinion, if the global GI color is set to a low intensity, the GI calculation seems faster. For the tutorial scene, RGB (190,174,142) and a multiplier of 0.1 are used. The background color simulates the background light of a studio environment. The GI algorithm must not sample a pure black environment.

Image 7 Advantage of the LC pass - physical correct lighting and quick preview:

Image 8:All effects added - quick test with noise threshold 0.01:

Image 9: Rendering with GI with LC and QMC - noise threshold 0.01:

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Global Illumination using LC and IM

A good way to increase the speed of the GI calculation is to jump from QMC GI to Irradiance Map mode. It's not easy to control and can produce some artifacts but if speed is necessary, than IM is the best choice. Image 11 is based on the options of Image 10.

Image 10: Options for Irradiance Map mode:

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The rectangular light option store with irradiance map is useful for blurring the noise of raytraced shadows. If too few subdivs are used, than the shadow looks blotchy. The example in Image 11 uses subdivs 6 - still a little bit blotchy. The DOF hides this a little.

Image 11: Fast GI Rendering with LC and IM:

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If GI artifacts with IM are visible, (i.e., in an interior scene), than my preference is to set the color threshhold to 0.15 and increase the samples to 64, 128, 256 or 512.

Color mapping

The human eye color mapping function is exponential - we can see details in deep shadows and in bright light. In the past, I have mostly used the "exponential" mapping for my projects. A new expontial mode is now possible - "Reinhard". The pure "exponential" color mapping function is too strong and the images look a little dull without postwork. The "Reinhard" color mapping mode allows you to choose a burn value to get the right balance between too much and too little contrast. The tutorial images show the new "Reinhard" color mapping and burn value 0.8.

The final rendering Image 12 is rendered with 8 subdivs for the shadows of the rectangular lights. The previous images are a little dark so I have set the brightness multiplier of "Reinhard" color mapping to 1.2.

Image 12: Final Rendering:

Copyright © by the contributing authors. All material on this collaboration platform is the property of thecontributing authors.

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Setting up Vray for linear workflow Summary By default, Vray 's color mapping is set to linear. This setting means that the render data is not altered before displaying it on your screen. But since monitors are not set up to respond linearly to this data, your renderings will have far too dark mid-tones. In other words, it will lead to renderings which are not phyically correct. This tutorial focuses on how to set up Vray to make more physically correct renderings. On the way, it will shed some light on Vray's quality control center: the QMC-sampler.

Introduction

First download the file LWF.rar (scroll down for a link to this file). Unpack the file, open and click render. You will notice that the rendering is quite dark. (please note that supplied file can slightly differ from the rendered images shown here, since some settings were lost after this tutorial was made)

In the VfB there is a small button with sRGB. Click on this button. You will notice that the scene is suddenly much brighter and shows much more detail. What's happening is that Vray now adjusts the data for yourmonitor.

r9 - 15 Jul 2006 - 21:53:47 - GijsDeZwart

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In general, a monitor does not respond linearly to input data. If it did, then the gamma of this monitor has a value of 1, a linear gamma, and you wouldn't need to use the sRGB button. Most CRT monitors have a default gamma of about 2.5. This means that the midtones are much, much darker when displayed then they should be. If you calibrate your monitor, you will most likely choose a gamma of 2.2 which is a worldwide standard. sRGB also assumes a monitor gamma of 2.2. Therefore this tutorial assumes that you have calibrated your monitor to work with a 2.2 gamma.

At this point you might wonder why you should bother thinking this gamma thing. Keep in mind that the textures, digital photos ,and scans you make are also adjusted to display correctly on your monitor. In other words, without you knowing it, they have been assigned a reverse gamma curve (1/2.2) to make them displaycorrectly.

In order to make physically correct lighting calculations (renderings) though, Vray uses linear data internally and also assumes that it is offered linear data to work with. This means that you should use textures that have their inverse gamma curve removed, or use textures that are created in linear space from scratch. Moreabout this later.

Setting up Vray There are two ways in Vray for Rhino to make physically correct renderings, each method having its benefits and drawbacks.

Method 1: using linear color mapping and the sRGB button

When using this method there are a few important things to note. Vray has a sophisticated rendering engine that heavily makes use of importance sampling and early termination (for an explanation see RenderingTerminology). Because of this, Vray uses less samples in dark areas then in bright areas. Since Vray is not aware of the fact that the image will be corrected for displaying after rendering, it will be neccessary to lower the noise treshold in the QMC sampler in order to get good quality renderings. Lowering the adaptive amount can also help.

NOTE: THE FOLLOWING IMAGES WERE RENDERED WITH PRE-CALCULATED LIGHTCACHE

Step 1

The image below shows the result with default QMC settings:

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adapt. amount noise thresh. min samples global mult. QMC GI

0.85 0.01 8 1 8

Step 2

Next, the noise threshold was cut in half.

adapt. amount noise thresh. min samples global mult. QMC GI

0.85 0.005 8 1 8

As you can see there is hardly any difference, both in quality and render time. This means that the noise threshold is no longer the limiting factor.

The reason can be found when opening the QMC GI tab. Its subdivisions are set at 8 (default).

Step 3

Set this QMC GI noise threshold to 20 and set the noise threshold in the QMC Sampler to 0.1 (ten times as big as the default noise threshold)

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adapt. amount noise thresh. min samples global mult. QMC GI

0.85 0.1 8 1 20

As you can see the result is very fast, but very noisy.

Step 4

Cut the noise threshold in half and re-render:

adapt. amount noise thresh. min samples global mult. QMC GI

0.85 0.05 8 1 20

Step 5

Again cut the noise threshold in half and re-render:

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adapt. amount noise thresh. min samples global mult. QMC GI

0.85 0.025 8 1 20

Step 6

Again cut the noise threshold in half and re-render:

adapt. amount noise thresh. min samples global mult. QMC GI

0.85 0.012 8 1 20

As you can see, the noise in the image is getting less and less and the render time more or less doubles when noise treshold is cut in half. If you look carefully you can see that the area shadows from the direct light have not improved mh from the previous rendering.

Step 7

Open the light properties and increase its subdivisions from 8 to 20. Also cut the noise threshold in half and re-render:

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adapt. amount noise thresh. min samples global mult. QMC GI

0.85 0.006 8 1 20

Method 2: using gamma correction color mapping

In contrast with the first method, you can also gamma correct your image during rendering. In this case, usingGamma correction colormapping, there are two values to set in the color mapping tab: the Multiplier and the inverse value. The multiplier acts as a global light multiplier. This means, if value is set to 2, you globally multiply the lights and GI in your scene by 2. Setting this value to 0.5, will decrease the lights and GI by 50%. The second value is the inverse gamma value of your display. In case your monitor is set to 2.2, this value has to be set to 0.4545 (=1/2.2). The nice thing about using this method is that Vray's QMC sampler is aware of the gamma correction in advance. This means that in contrast with the first method, you get higher quality renderings with default QMC settings. This also means that with default settings, images will take longer to render than with the first method.

Step 1

The image below shows the result with default QMC noise threshold at 0.1 (similar to step 3 with Method 1)

adapt. amount noise thresh. min samples global mult. QMC GI

0.85 0.1 8 1 20

Step 2

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QMC noise threshold cut in half (similar to step 4 with Method 1)

adapt. amount noise thresh. min samples global mult. QMC GI

0.85 0.05 8 1 20

Step 3

QMC noise threshold cut in half (similar to step 5 with Method 1)

adapt. amount noise thresh. min samples global mult. QMC GI

0.85 0.025 8 1 20

Step 4

QMC noise threshold cut in half (similar to step 6 with Method 1)

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adapt. amount noise thresh. min samples global mult. QMC GI

0.85 0.012 8 1 20

Step 5

QMC noise threshold cut in half and light subdivisions set to 20 (similar to step 7 with Method 1)

adapt. amount noise thresh. min samples global mult. QMC GI

0.85 0.006 8 1 20

Step 6

Setting QMC noise threshold back to its default (0.01) gives similar render time/quality compared to the last image from step 1:

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Linearize textures

As mentioned earlier, Vray needs to be offered linear data to make physically correct renderings. This means that either you correct your textures or make them with a linear profile from scratch.

Most textures can be corrected the easy way by overriding the bitmap gamma in the bitmap loader. If you make a new material, and add a texture to the diffuse color slot, you should use the following settings:

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Just note the gamma override setting. By doing so, you will 'remove' the burned-in gamma correction from the image, which effectively linearizes the image.

One way to correct textures to linear gamma is to convert them to 16 bit mode, then convert to a linear profile. In Photoshop, you can convert to 16 bit using the menu: Image --> Mode --> 16 bits/Channel. Then convert it to a linear profile (in menu: Edit --> Convert to Profile... then select a linear profile like AIM RGB =Trinitron D65 G1.00. This profile can be downloaded here. Look for AIM Working Spaces. For installation, refer to your Photoshop help file.)

Rendering with textures applied

For example, this is what a rendering without corrected textures could look like...

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...and this is after correcting with 'override gamma' for all textures at 0.455:

If you consider the following textures were used, it is clear that the gamma corrected textures resemble to original files much better. (textures shown here were made smaller for displaying here)

Further reading: To learn more about gamma correction you can read the article Linear workflow reloaded.

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-- GijsDeZwart - 29 Jun 2006

Copyright © by the contributing authors. All material on this collaboration platform is the property of thecontributing authors.

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General Vray for Rhino tips and tricks Not every small trick needs an entire tutorial. Here is a collection of some small helpful tricks. Please post what you like.

(1) Secondary ray bias Sometimes it is useful to model intersecting objects. If no bias is used, than Vray marks the intersection black. To avoid this black artifact it helps to set a secondary ray bias and a bias in the shadow properties of all lights.

Secondary Ray Bias against artifacts of intersecting objects:

(2) The best basic book about rendering ... ... can be found here - http://www.3drender.com/. It's a must for every beginner.

(3) Multilayer materials - an example Example of a material with textured layers (the line around the mirror show the rhino geometrie):

(4) Image Based Lighting (IBL) The V-Ray for Rhino texture editor can be used to load high dynamic range images (HDRI) as GI and

r14 - 09 Aug 2006 - 20:31:01 - MichaelMehnert

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Background maps of your scene environment. The HDRI image will be used to illuminate the geometry in your scene. To understand more about IBL, see Paul Debevec's website and a tutorial he has made tutorial.

Files

Download Starting Scene FileDownload HDR File

Steps

In the V-Ray for Rhino RenderOptions > EnvironmentSettings ? , select the "m" button to use a map instead of a floating point color.

1.

In the V-Ray for Rhino Texture Editor, in the Common section, set the map type as Bitmap.2.Under the Bitmap section, choose "m" and locate the a0020.hdr file. (Currently only HDR file types are supported)

3.

Select Environment mapping type from the UVW section. Choose the Mirror_Ball mapping type for this HDR image.

4.

Use the Multiplier to control the amount of light being transmitted by the HDR image. In this case we set it to 1.5.

5.

Follow steps 2-5 for setting the reflection map.6.

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(5) Flat glass for architecture or ... Don't use caustics for architectural exteriors. For windows, a single surface with an reflection (fresnel) layer only is usually good enough. For flat glass, like that found in glass cabinets with a light color, use anadditional refraction layer. Set the IOR to 1 and enable affect shadows. So the glass acts like a semi-transparent object without refractions and a colored shadow.

(6) Full adaptive image sampling Many quality options use the parameter "subdivs". This parameter controls the quality of soft shadows, blurry reflections/refractions, and the DOF (Depth of Field)effect. All these parameter can be ignored if Vray is set to Full adaptive mode. In this mode, the Vray engine is using so many samples (see attached screenshot - 0 .. 50 samples), that a specific noise threshhold is reached. Recommended 0 ... 100 samples. If the user gets the feeling that too many samples slow down the calculation too much, fewer samples can be set - 0..50 or 0 .. 20.

The full adaptive mode dosn't influence the IM prepasses. If the arealight option "store with IM" is used, than the subdivs of the arealight must be extra controled - for example set at 9 or 12 or 16. This values areused for the IM prepasses.

AdaptiveSampling ? .jpg:

(7) Brushed Metal A basic material for design work - brushed metal. But which parameter is more important: glossiness (blur) or anisotropie? The test renderings should give the answer.

Test of different parameters of anisotropic reflections:

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(8) Color mapping - Reinhard

The "Reinhard" color mapping mode can be used for any rendering between "linear" and "exponential". If the burn value is 1, than the linear mode is used. But often details are lost in the brightest areas of the image. A lower burn value gives a shift in direction of the exponential mode. A burn value of 0 lets VfRkeep all image details, but the image could look dull. A good starting value is 0.5.

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SSS in V-Ray for Rhino Summary enter text here test wouter

General

Before going into detail about vfr options to create translucent materials, it's best to have some basic knowledge about what translucency is.

http://www.neilblevins.com/cg_education/translucency/translucency.htm

Translucency is the effect of light passing trough and scattering inside an object. Normally in 'simple' vray materials, light hits a surface, and bounces off to a certain degree. With refractive materials, light rays also pass trough the surface, bending under a certain angle (IOR). If translucency comes in, the refracted ray doesn't simply run straight through the object, but instead it gets scattered in all directions. Examples of real life stuff where translucency is very visible are candles, grapes, orange juice, skin, leaves, paper, etc ...

candle:

juice:

r6 - 25 Jul 2006 - 22:39:17 - WouterWynen

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juice_02:

plastic:

paper:

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When looking at the images, one very important factor can be seen: the placement of the lightsource. Translucent effects are especially visible with strong lights, placed inside or behind an object. For example the orange juice, the translucent effect is almost gone in the picture where the light is much more even. It'sstill visible, but much more subtle than when you light it with a flashlight.

Another thing to note is the thinner the objects, the easier it is to see the translucent effect..

Besides the examples shown here, other situations where you would like to have translucency are when some objects are trapped inside of each other. For example the bones in the human body, or the seeds in grapes. When you hold a strong flashlight under your hand, you will notice the hand will light up red, and you will see where your bones are located because they don't let light trough and therefore will be much darker. Same for grapes, if you light them from behind it will become clear that there are seeds in them, which isn't obvious when lit with a normal even lightsource. In the flesh example, the color turns red because of the blood it it, while the surface color is pink/brown. So for all these cases, translucency can be used to recreate the effect in your rendering.

Absorbtion Let's start with the real thing now. First of all, we will create translucent effects without using translucency. Sounds silly, but it's not.

To do so, we will use the absorbtion property of the vray material. In vray, this is called 'fog'. The basic theory is that when a light ray hits a refractive surface, it gets bent off, and travels further trough the surface, to come out on the other side. With absorbtion, the ray looses intensity the further it travels trough the object. What this means is that the thicker the object, the more energy is lost, the darker it will appear. So if you have an object with thick and thin parts, the thin parts will be very transparant, and the thick parts will look more opaque (or dark transparant).

Images 0201 and 0202 show the difference between the usage of a refraction color or a fog color. The firstuses a red refraction, and white fog, and the second uses a white refraction and red fog. As you can see, the second one is much nicer.

* 0201:

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0202:

Now we will use this fog effect to create translucent looking materials.

Open the scene absorbtion_start.3dm. The scene has a dim skylight, GI is on, two rectangular lights placed behaind the objects. I used some low quality settings to speed up rendering. In color mapping, gamma is set to 2.2. Read the LWF tutorial for more info on this. Gamma 2.2 is crucial to get translucency to work well. The objects have the material from the previous renders, nut without the reflection layer, as we don't need that right now. You can see that I used a medium red color for fog, with a 0.2 multiplier.

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Render the scene, you'll get image 0203. Play with the fog multiplier to see how it affects the transparencyof the material.

* 0203:

To get the translucent effect, we will now turn on 'glossy refraction'. You turn it on by simply setting the glossiness lower than 1.0. Try 0.8 for now and render. See image 0204.

* 0204:

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Now try glossiness set to 0.5 and render. See image 0205. Starting to look more like translucency now!

* 0205:

Now we will lower the refraction IOR. Set it to 1.1 Image 0206

* 0206:

Now try a medium grey refraction color. Image 0207

* 0207:

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You see that with all these settings, you can already get a lot of effects. The lower the glossiness, the moreblurry the refractions will be. The darker grey the refraction, the less light will pass trough. Fog multiplier determines the effect of the fog color, low values will wash out the color, high values will make it stronger.

Image 0208 is rendered with some different settings, and with better quality. This is the result when you render scene absorbtion_step_01.3dm

* 0208:

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Translucency Now open scene absorbtion_step_02.3dm. I reverted back to low quality settings. Turn on translucency in the glass material and render. The objects will be black ...

Go to the options tab of the material, and turn off 'double sided'. Render again, we now have a true translucent rendering! Image 0209

* 0209:

Change glossiness to 0.8 and render. Image 0210. You see the effect of this is quite similar than without the translucency turned on.

* 0210:

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Change refraction color to a very dark grey (30,30,30). Render. Image 0211. * 0211:

Also try a very light grey. Image 0212.

* 0212:

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Experiment again with different combinations of refraction color (go from white to black, only greyscales), fog color, fog multiplier, glossiness. I use only greyscale for refraction color to keep the number of colors to a minimum. Simply see the refraction color as some kind of transparency control, dark is opaque and light is transparent. So the color now is only controlled by the fog color.

Usually translucency is a combination between a surface color and the color inside the object. Untill now, we didn't use the diffuse color at all, its transparency control was set to pure white, meaning 100% transparent. For example to create flesh, you need the combination of the pink/brown skin and the deep red of the blood.

Open scene absorbtion_step_03.3dm. Render. Image 0213.

* 0213:

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Look at the material settings. A lot like before as you can see. The goal now is to create a flesh material. As you can see here, the rendering looks like the blood only ... The diffuse flesh color isn't showing trough.

I already changed the diffuse to something like a flesh color. The only problem is the transparency control for the diffuse layer. We need to turn this into a more dark grey, so that some of our diffuse layer will also show up. Set it to a 70,70,70 grey and render. Image 0214.

* 0214:

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As you can see, now almost only the diffuse shows, only in the thin parts the blood color comes trough. This is more how flesh behaves. The lighter you set the diffuse transparency slot, the more the blood will show trough.

Here's a higher quality image I made: Image 0215. Open scene absorbtion_step_04.3dm if you want to see the settings I used.

* 0215:

There are two parameters in the translucency option, scatter coeff and fwd/bck coeff. I always set them to 0.5, because I don't really know what they do. ;o)

The thickness parameter controls how deep light can penetrate inside the object (in units). I always leave this at a high value, because I rather control how deep it should go with the refraction color and fog multiplier.

Here's a summary of how I use the translucency settings:

First determine the diffuse color of your material. Test it under normal lighting to see if it looks right.Then think of the color inside the object. Is it different than the diffuse or not? If not, make your fog color similar to your diffuse. Sometimes a less saturated version of your diffuse works well. If the inside color is different, then choose your fog color as you wish. Try to avoid rgb values of 255. If you want a white fog, use a light grey instead.Then make up if the material top surface is very transparent or not. If not, a lot of the diffuse will show up and not much of the inside. So you need a dark transparency color for your diffuse. Use only greyscale here. If the top surface is very tranpsarant, use a lighter transparency color. For example for skin use a pretty dark diffuse transparency, for grapes you can use a lighter transparency. The grape surface is more transparant than the skin surface.Then think about the inside again. Is this very transparant? If yes, use a light grey refraction color. If not, use a dark grey. If the inside material is the same as the outside, I recommend using the same refraction grey as you used in the diffuse transparency slot. Use only greyscale values here,

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otherwise you'll get a color mix with your fog color which usually results in unexpected looking materials ...So the fog color and its multiplier are also important here. Low multipliers will reduce the fog effect,also washing out your fog color. There is a difference too between a light, unsaturated fog color with a high multiplier versus a dark saturated fog with a low multiplier. This is however a bit unclear and can confuse you a lot. I usually use a medium saturated, medium dark fog color.Then use the glossiness parameter to control how much the light should scatter inside the object. The higher the glossiness, the more straight the light will travel. The lower, the more the light will scatter around.Test render a lot, because the material will look different under varying lighting conditions. So the material preview will not be that accurate because your scene will probably bet lit very differently.Remember that to see the translucent effect, it's best to back light your objects. You don't see translucency of flesh under normal lighting conditions, but you do see it if a bright spot shines behindyou when you stand in a dark room (for example an actor on a theater stage).Translucency is very time consuming. You need high subdivs to get it clean ... Only use it when you really need it!

Here are some translucency examples quickly created in Vray for Rhino. Note that they can be optimised alot probably...

candle:

paper:

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wheels:

Examples files: candle.3dm: candle.3dm

wheels.3dm: wheels.3dm

paper.3dm: paper.3dm

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absorbtion_start.3dm: absorbtion_start.3dm

absorbtion_step_01.3dm: absorbtion_step_01.3dm

absorbtion_step_02.3dm: absorbtion_step_02.3dm

absorbtion_step_03.3dm: absorbtion_step_03.3dm

absorbtion_step_04.3dm: absorbtion_step_04.3dm

absorbtion_fog_vs_refraction.3dm: absorbtion_fog_vs_refraction.3dm

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TWiki > VfR Web > UserTutorials > TutorialJ

Creation of full spherical renderings and VR Quicktime movies Summary Tutorial for creation a Quicktime Virtual Reality (QTVR) movie per VfR spherical camera.

Introduction The creation of a full 360° spherical Panorama can be done very simple in VfR: the camera must be placedin the middle of a room (image (2)), for example in typical hight of the huma eyes (image (3)) and at the VfR camera options must be selected "spherical" and "override FOV" with 360° (image (4)). Ready torender. The camera control can be set "visible" per right mouse button click on the viewport name.

(1) Rhino3D example scene - a photo exhibition:

(2) Scene in Top view:

r3 - 26 Jul 2006 - 13:25:43 - CoreyRubadue

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(3) Scene in Front view:

(4) Camera options for 360° spherical renderings:

Image (5) show the downscaled Panorama rendering. Attention: some QTVR creation tools need images ratio of 2:1. The original render size of the example is 1600x800.

(5) 360° Rendering:

The conversion of the panorama image to a QTVR can be done per different tools, for example per free tool PanoCUBE. The PanoCUBE ? files contain a "script.txt". Here can be set some parameters for the QTVR like the output size or image quality. My experience is, that the height of the movie should be not higher than the half hight of the rendering. So, the QTVR show per default the image pixels without up or down scaling (a scaling of the QTVR window stay possible). If the rendering is 1600x*800*, than the

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created movie size should be not bigger than *400*x300 (4:3 QTVR output ratio).

(6) Creation of the QTVR per free tool 'PanoCUBE' - drag&drop of the rendering to the PanoCUBE ? .exe:

(7) Screenshot of the QTVR :

QuickTime Movie (400k)

At the world wide web can be find much panorama tools. For example this website provide a html code creation for publish per Java viewer - http://www.0-360.com/publish.asp.

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TWiki > VfR Web > UserTutorials > TutorialK

Caustics in V-Ray for Rhino Summary enter text here test wouter

Introduction

Caustics are the nice lighting effects you see around reflective or refractive objects. The smaller your lightsource (or the further away you place it), the sharper and nicer your caustics will be. Here are two examples of refractive caustics.

The first example is a wineglass, lit by the sun: very sharp and nice patterns. Light gets refracted and where a lot of light is bundled, you get these bright patterns.

The second example is the same glass, this time lit by the sky trough a large window on one side (meaninga larger lightsource): blurry caustic patterns

r2 - 26 Jul 2006 - 13:29:04 - CoreyRubadue

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Here an example of reflective caustics. The first one is again lit by the sun:

And the second one lit by the sky/window again:

This image shows the typical pattern a reflective ring produces:

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CG caustics

In vray, you have many ways to let caustics show up. Every method has its advantages, and it all depends on how important the caustic effect in your rendering should be.

What you should remember is that all methods try to do the same thing, so you shouldn’t mix two methodsor you can get a double caustics effect. Usually vray will automatically turn of one method if you turn onanother. More on that later.

Refractive caustics

Starting with refractive caustics, because this is used a lot and it also has the most methods to createthem.

One of the frequently asked questions in rendering with Vray is "why isn’t the light going trough myrefractive objects???" In most not so advanced renderers, transparent objects do let light trough by default.In fact, this is a fake caustics effect, and many people don’t realize that. Then they start using vray, andimmediately notice that for example a glass material is casting a pure black shadow.

Open scene caustics_01.3dm. There is a groundplane, and 3 objects with a glass material. I also added a point light with default settings. Render the scene, this will give you this image:

Clearly this is not how you would expect glass to behave. There are three ways to let light pass trough transparant objects, or in other words, to generate caustic effects:

fake it with the fog material parametersGI causticsPhoton mapped caustics

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Fake refractive caustics

Since now we are not yet using GI, we will look at the other 2 options first. To get the effect you are probably used to in render engines like for example flamingo, we must use the fake caustics method.

Go to the glass material properties, and then in the refraction rollout, tick the option ‘affect shadows’. Thismeans, the fog options will control the transparency of the shadows. Render the scene again and you getthis image:

This is how transparent shadows look in most render packages. In fact, these are fake caustics and it looks very different than in real life. It is good though if you want your lights to pass trough windows for example.

refractive GI caustics

The fake caustics are only usefull when using ‘artificial’ lights, like rectangular lights, spots, pointlightsetc… If you are only using a skylight or environment HDRI to light your scene, the affect shadow option willnot do anything, and you will need to use GI caustics to let light pass trough glass. Open scenecaustics_02.3dm. There is a tube with a glass plate on it. The scene has basic GI turned on, lighting is done by a light blue environment color. If you render the scene, you get this image:

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As you can see, the inside of the tube is not black, so in fact light is coming trough the glass plate! Tryturning on and off the ‘affect shadows’ option for the glass material. As you will see, this has no effect atall. You should remember that this option is only used for what is called ‘direct light’. This is light comingfrom the rhino light types. Skylight, hdri light and rectangular lights with the ‘store with IR map’ optionturned on, are all not direct light. These last three don’t produce direct light, but GI light (calculated withwhatever method you set in primary GI engine).

The reason that the skylight is able to go trough the glass plate in this file, is because by default an optionis turned on to do so. In the vray render options, in the Indirect Illumination rollout, there is an option to turnon ‘refract caustics’. Turn this off and render again. You will get this image:

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The inside is very dark now… So this option is very important for interior renders where you want yourskylight to pass trough glass windows!

As said, with point lights, spot lights and directional lights, you must enable the affect shadows option to letlight pass trough your objects. The rectangular light is an exception. Altough it produces direct light also,vray is capable of calculating GI caustics from it. In other words, you don’t have to use the affect shadowsoption to let the rectangular light pass trough your glass objects. To demonstrate this, open scenecaustics_03.3dm.

Render and you will get this image:

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The scene has GI turned on, and is lit only by a rectangular light (no skylight). You will see that the objectsall cast a black shadow, which is not what we wanted. The problem is that for vray to calculate real GIcaustics, you need real light settings too. If you look at the rect light properties, you will see that by default,the ‘no decay’ option is checked. In real life, every lightsource has inverse square decay. So turn off the ‘nodecay’ option in the light. The light will now have an inverse decay falloff. This means that the further awayfrom the lightsource you place objects, the darker they will be. If you render right now, the whole scene willbe black… Because the light has now a falloff, you will need a higher multiplier for the light to reach ourscene objects. Set the light multiplier to 60 and render again. Now you get this image:

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As you see, the light passes trough the objects, but it is splotchy. Since these are GI caustics, the quality is controlled by your GI settings, which are very low for the moment. Here is an image with higher GI settings:

And the scene for you to study: caustics_04.3dm

Results are still pretty low quality, which is because caustics are not that easy to compute with the GI engines. GI caustics are mainly used to avoid dark areas in renders lit by a skylight only. For example thesurface underneath a glass table top, or the inside of an interior scene behind glass windows.

Photon mapped refractive caustics

If you want very good and physically correct caustics, you should use ‘photon mapped caustics’. Opencaustics_05.3dm. There’s the glass objects again and a point light. Render the scene and you’ll get thisimage:

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We want realistic light passing trough the glass objects, so we need photon mapped caustics.

In the vray options, go to the caustics rollout, and turn on caustics. Render the scene, nothing hashappened… Also here, we need an inverse square decay option for the light source or it won’t work. Go tothe point light and choose inverse square decay instead of linear. Like before, we will also need to increasethe light strength. Choose 15000 for the light multiplier. Render again, you get this image:

The caustics you see now are photon mapped caustics. They are not computed with the GI settings at all, but a with an independant system.

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Now we want better quality. Take a look at the caustics rollout settings. From the helpfile:

Multiplier - this multiplier controls the strength of the caustics. It is global and applies to all light sources that generate custics. If you want different multipliers for the different light sources then you should use the local light settings. Note: this multiplier is cumulative with the multipliers in the local light settings.

Search dist - when VRay traces a photon that hits an object in some point the raytracer searches for otherphotons on the same plane in the surrounding area (search area). The search area in fact is a circle with center the original photon and its radius is equal to the Search dist value.

Max photons - when VRay traces a photon that hits an object in some point and counts the photons in thesurrounding area it then averages the illumination of that area based on the number of the photons in it. If the photons are more than Max photons VRay will only take the first Max photons of them.

Max density - this parameter allows you to limit the resolution (and this the memory) of the photon map. Whenever VRay needs to store a new photon in the caustics photon map, it will first look if there are any other photons within a distance specified by Max density. If there is already a suitable photon in the map, VRay will just add the energy of the new photon to the one in the map. Otherwise, VRay will store the new photon in the photon map. Using this options allows you to shoot many photons (and thus get smoother results) while keeping the size of the caustics photon map manageable.

For sharp high quality caustics, you should make sure that not too much surrounding photons are blended together. The max photons is important here. Lower this to 10 and render again. You get this image:

Still no good, but you can see they are sharper already.

The other main parameter for high quality, is an option you must set on each light. Go to light properties of the point light, and note the caustics subdivs (not photon subdivs!!!). Increase this to 2500 and render again. You get this image:

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Probably we lowered the max photons too much, we will never get it smooth now. So change it to 25, and set caustics subdivs of your light to 5000. Now you get this image:

That’s looking better! Download the scene with these high quality settings here: caustics_06.3dm

Max density can be used to limit the photon map size a bit. It will make sure that not too much caustics will be stored in the same location.

Here some examples of what the other settings do:

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http://www.spot3d.com/vray/help/VRayHelp150beta/examples_caustics.htm

If you don’t want to use inverse square decay on the light, you must enter a very high caustics multiplier(instead of a very high light multiplier). For example in this case, linear decay with light multi=1, would need15000 for caustics multiplier to get evenly bright caustics as in the previous test.

Some notes: caustics are best visible with small lightsources. Ideal is the pointlight. Rectangular lights have a bigger area, the caustics will be softer, and also more difficult to compute.Sometimes caustics are unwanted! Mostly they are not used, and if they are used, it is to let light pass trough straight glass planes. One area where caustics are important is jewelry, and therefore photon mapped caustics can be very usefull. In most cases, low quality GI caustics will be more thanenough.

Reflective caustics

All things already said are also true for reflective caustics. The only difference is that here you don’t havethe fake type, and that these caustics are generated by materials with a reflective layer in them.

Reflective photon mapped caustics were in fact already present in the previous examples. The glass has a reflection layer too, so some caustics came from that. Look at our last rendered image, on the other side ofthe objects. Some bright spots can be found on the floor there, these are reflective caustics.

Open scene caustics_07.3dm, and render. You get this image:

I used the same lighting setup as before. But now there is a chrome ring in the scene. You can clearly see the reflective caustics on the inside and outside of the ring.

To get the same thing, but with reflective GI caustics, we need to replace the point light with an area light (remember GI caustics only come from non direct light, exception is the rectangle light, also called area light).

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Open scene caustics_08.3dm. The same ring, and photon mapped caustics is turned off. Area light insteadof point light. If you render, you get this image:

No caustics? Simply turn on the ‘reflective caustics’ in the indirect illumination rollout. This is off by default!!Render and you will get this image:

Very low quality... Here is an image with better quality GI caustics:

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Open the scene: caustics_09.3dm to look at the settings. The quality is controlled by the GI settings, which is not the goal of this tutorial.

Notes: You can turn on or off reflective and refractive GI caustics. But you cannot turn off only reflective photon mapped caustics. So with photon mapped caustics, it is either both on or both off!You cannot generate photon mapped caustics from skylight lighting.If you enable photon mapped caustics, the GI caustic creation is automatically disabled. Otherwise you will get a double caustics effect.Same for the affect shadows option. If you have photon mapped caustics enabled, the affect shadows option will not be used anymore (this is for refractive caustics only of course)

To finish this tutorial, here is a wineglass render with very high caustics subdivs:

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And the scene if you wanna take a look at it. Note this will take some time to render... Also try to render this scene with caustics disabled, so you can see the difference better. caustics_10.3dm

Files used in the tutorial:

caustics_01.3dm: caustics_01.3dm

caustics_02.3dm: caustics_02.3dm

caustics_03.3dm: caustics_03.3dm

caustics_04.3dm: caustics_04.3dm

caustics_05.3dm: caustics_05.3dm

caustics_06.3dm: caustics_06.3dm

caustics_07.3dm: caustics_07.3dm

caustics_08.3dm: caustics_08.3dm

caustics_09.3dm: caustics_09.3dm

caustics_10.3dm: caustics_10.3dm

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TWiki > VfR Web > UserTutorials > TutorialL

Image based lighting (IBL) with HDRI Starterkit step by step This tutorial should beginners help to get a quick start with Vray for Rhino. This is the second Edition of myStarterkit with some improvements. Please download the scene file and the maps. The scene of the Starterkit is very simple - a test object and ground with soft background.

Rendering of the Starterkit (LC+IM):

At the enviornment options are setup two versions of a HDRI. The first image is downscaled and blurredHDRI for GI lighting the scene. The preblur helps to keep the noise low and to accelerate the calculation. The downscale of the image helps to save memory. Preblur and downscale are very important for a good speed. HighRes ? HDRIs are necessary only, if it is visible in the background. The background environment is set to the original selfmade HDRI. Physical correct is, to set both HDRIs at the same options (brightness, gamma ...).

Image Sampler and QMC Sampler. The Image sampler is set to "adaptive QMC" and a high "MaxSubdivs", because the scene is setup at the "QMC Sampler" options in full adaptive mode (adaptive amount 1). So, it is possible to use at all other subdivs options at the default value. Vray automatic use so much samples until the "noise threshold" is reached. This is the most important option of the file. A threshold of 0.05 is good for a fast raw preview and 0.005 is good for high quality images with very less noise. Most 0.01 should be good enough.

The color mapping is set at "Reinhard". In this mode it is possible to render an image in linear mode (burn value 1) or exponetial mode(burn value 0) - values between 0 and 1 are fine. The difference between "exponetial" and "linear" is like between the human eye and a cheap CCD camera. The eye can accept a very high light contrast, details are seen in shadows and lights, but a CCD camera has problems to get heaven and earth at the same image. But burn value 0 is very heavy and the image could look dull. A goodstart point is burn value 0.5.

The Indirect Illumination is set at Light cache for secondary engine and QMC for primary engine. This is the slow and easy mode. The quality of the image is determinated by the noise threshold and LC subdiv

r3 - 12 Sep 2006 - 19:23:57 - MichaelMehnert

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count only. How do it work? First will be calculated the LC, a physical correct method to calcualte the lighting of a scene. The subdivs options set the count of LC samples - 1000 is good allround setting. During the LC pass the whole scene is visible and the user can see the lighting, materials and objects within a few seconds. A good first control over the scene. After the LC is calculated, the primary engine starts to calculate the scene based on the LC. In QMC mode each point in the scene will be calculated without sample approximation. Slow, but very stable. Artfacts and small details are not a problem. Good forbeginners. ;o) If more speed is needed, the user can jump from QMC to IM. This is a classical fast method,the GI will be calculated in passes with approximations. Some times artefacts will be visible and the user must correct the IM options like sample count. Both primary engines are set in the file to best parameters,so it is possible to select one of the both modes.

Good, stop here. If more infos are needed, please ask here and I will update the tutorial.

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TWiki > VfR Web > UserTutorials > TutorialM

Materials Introduction The material editor can be open per Rhino3D menu "Vray" -> "Material Editor". Per right mouse button (RMB) click on the "Scene Materials" materials can be imported, added new or purged unused materials. Amaterial can based on four layer types - emissive, reflection, diffuse and refraction. A layer type can contain unlimited layers. All layers are in order like placed on the material from top to down. The default material contain one acitve diffuse layer. Additional layers can be placed per RMB click on a layer type. The preview window dosn't show the current selected material, it show the last rendered preview.

All example renderings are done in full adaptive mode and noisethreshold 0.02 (good preview quality).

Screenshot of the VfR material editor:

If the user like to see the difference between two material settings per preview, than the prepass of thepreview window should be disabled per RMB at the preview window.

Extra controls of the preview window:

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Diffuse material

Simple to create and fast to calculate - the diffuse material. It looks like loot (Plasticine®) or a dull plastic.The color can be set per Rhino color chooser or texture editor. The edito will open per mouse click on the little "m". Textures are using the map channels of the McNeel ? mapping tool (RCM).

Single diffuse layer material:

Shiny plastic or Ceramic material

If we add a reflection layer and set the reflection map type to "fresnel", than we get shiny material like shiny

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plastic or Ceramic. The IOR is a material specific parameter and can be find for example at this list here (link wanted). The refraction parameter can be ignored here, it is a current interface issue. A basic rule forshiny plastic is, that the reflections are not tinted by the material color. * Fresnel control of the reflectivelayer:

Shiny plastic material:

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Rubber material The standard diffuse material looks dull, but for Rubber it should not be used. Rubber show very blurry speculars and so it is better to use the shiny plastic material with blurry reflections. Here an example with glossiness 0.5.

Rubber material:

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Rough material Often used for Rough materials is a special render model based on the theory of Oren-Nayar. Typical examples of rough surfaces are the moon, felt, cloth, clay ... . All this materials seems to show a light distribution particular independent from the direction of the light. Extrem samples of this materials are looking flat, sometimes like textured emitters without self shadowing. At the moment Vray dosn't support an Oren-Nayar shader, but it can be good simulated (not faked!) by a single reflection layer (no fresnel) with a very low glossiness of 0.1. A side effect is, that the material color will be show much darker as in the Rhino color chooser (this is right - more infos at this forum thread. To get the right color back it helps to use the "Acolor" texture type and the multiplier (here set at 2). This material need some time to calculate,but is good for special cases.

Rough surface material based on a single reflection layer:

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Here an image from a rough surface test. In comparsion from left to right: diffuse material, material withfine noise bump and low glossiness reflection layer material.

Rough material method test:

Architecture glass material The simpliest fake of glass for fast calculation is to set a material with single reflective layer and Fresnel "map". This material can be assign to a single plane, for example placed in a window.

Material with single reflection layer (Fresnel controlled):

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If a colored glass is necessary, than a refractive layer with refraction color must be add. In the past it was possible to set the refraction IOR 1 and to assign the material to a single plane window. This dosn't work now. So, for colored window glass two planes with normals outside are necessary.

Glass material The standard glass material based on a reflective layer (Fresnel enable) and a refractive layer. If a refracation color is set, than the glass looks constant tinted independent from the thickness of the object.

Glass with refraction color:

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More interesting is to use the fog color instead the refraction color. Now the color of the glass depends onthe material thickness. The fog multiplier helps to control the intensity of the volume effect.

Glass with fog color:

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If GI without refractive caustic is used or an image without GI/caustic is rendered, than the shadows ofglass objects are black. The option "affect shadow" makes that the shadow is tinted by the refraction or fogcolor. This method helps to avoid long render times for caustics and to get a faked colored shadow instead. The option "affect alpha" control the color of the glass in the alpha map- without "affect alpha" glass is not transparent.

Option "affect shadow" in action:

The glossiness option allow to blury reflections/refractions - good for effects like frozen glass.Frozen Glass effect by glossiness 0.7 at reflection and refraction layer:

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For infos about SSS per translucent option please look at Wouters SSS tutorial. Her only an example. Translucent material:

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Options for a translucent effect.gif:

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Trick: if the SSS effect is to dark, than it helps to use the "Acolor" map or the used texture at multiplier 2.The right balance between diffuse and translucent brightness can be set per transparency of the diffuselayer.

Metal material

Metal reflect the environment and tint the reflection by the color of the metal. Two options control the color of the material. The reflection color control the intensity and the transparency, for example a color value 200 of 255 mean 80% reflectance and 20% transmittance. The "filter" color set the color without affect the transparency. For example a plane with single reflection layer: a yellow (RGB - 255,255,0) reflection color makes that Red and Green will be reflected and blue go through the plane. A yellow filter color makes, thatRed and Green will be 100% reflected and Blues is blocked.

Reflection color vs Filter color:

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A good workflow seems to be, to use the "filter" for color effects and the "reflection" for "fresnel" ortransparency. Attention: if the reflection color is set to less than 100% or to "fresnel" than a second layer behind should limit the light rays. Attention: if the diffuse layer as last layer is forget, the rendertime will much more longer.

Simple metal material without fresnel control, blur or second layer:

If we look around we will see that metals show more than one reflection layer. Sometimes good visible aretwo layers - a very blury reflection plus a clear reflection. Very good to see at aluminium. The reflections of dark parts of the environment are "broken", the darker colors are overlay with a glow.

Example of used metal - aluminium:

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We get the effect, if we combine two reflection layers. Here an example of a complex metal material.Metals has typical a high IOR, so it is set to 20 at both layers. The reflection color of the first layer is set at value 125 (~50% - set at the fresnel color), so the next layer behind is visible too. This layer and the next use the same material color that tint the metal. The first layer show the clean reflections (glossiness 0.98) and the second the blury (glossiness 0.8). At last, a colored diffuse layer stop the light rays. An additional bump helps to get a "imperfect" look.

Options of a two-layer-metal - combination of clear and blur reflection :

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Example of a two-layer-material with a small bump:

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A disadvantage of the two-layer-material is a longer rendertime. Here helps a simplification, the secondreflection layers will be disabled and replaced by a diffuse layer in metal color. It has not the subtle glow of the complex two-layer-material, but looks more real as the single layer material.

Metal material with additional diffuse layer:

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If the colors of the two-layer-material example are replaced by textures, than use or old metal can becreated. Here an example with a brass texture.

Options of a two-layer brass material:

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Brass material (longer rendertimes by higher noise threshold 0.005):

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Brushed metal Often used for Design objects - brushed metal. VfR direct support anisotropic reflections.

Simple brush metal per anisotropic reflections:

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The anisotropic reflection stretch the reflection blur only, stripes of the small scratches are not visible, atexture map is needed (for future releases the procedural noise could be used). Here an example, the texture is placed at the filter color map.

Options of a brushed metal with scratch texture:

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Textured brushed metal:

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Test with bump maps has shown, that much calculation time is needed to clean up the reflections. So, thebump method is recommended for closeup shot only.

Brused metal with additional bump map:

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Test of different options for brushed metals:

The "rotate" option helps to turn turn the bruseffect. Attention: if the brush effect should be turned 90°, than

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rotate 180° must be set. ( VfR 1.0 Bug?)

Metalic Carpaint

Nice looking and fast created - carpaint with two reflection layers. The first layer is fresnel controled plastic reflection (IOR1.55) and simulate the clear finish. The second reflection layer is a blury metalic reflection with a tint (filter color).

Options of a Carpaint material:

Carpaint material:

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Ceramic Tiles Often a texure need three texture controled layers - diffuse color, reflection intensity and bump. Here an example of a ceramic tile material. Color and bump can be straight be set, but more attention need the reflection. In simple cases the bump map can be used for the reflection map. In the example here the gapsbetween the tiles must be non reflective, so a black color in the map is needed. The reflection map of a non-metal material must be set at the color of the fresnel map like shown in the screenshot.

Parameters of a ceramic tile material

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If the rendering dosn't show a good bump effect in GI mode, than the IraddianceMap ? mode should be avoided. This mode smooth the lighting and hide small details. The QMC GI mode show all details of the bump.

Bump mapped material with IM GI:

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Bump mapped material with QMC GI:

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Emitter Material Emitter materials need one emissive layer only. If a color is set than the intensity option control the brightness. If a texture map is set, the multiplier of the texture control the intensity of the textured emitter.

Options of a textured emitter:

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Textured Emitter - upps - this is fast rendered ;o) :

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2D Billboards Billboards are simple planes in virtual scenes with mapped peoples, animals or trees. The material is simple - a textured diffuse layer and a transparency map. VfR need transparency maps, but often alpha maps are to get. No problem, only the "invert" option must be set at the transparency map.

Options of a Billboard woman:

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Rhino3D Screenshot of a Billboard scene:

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Rendered Billboard people and tree:

A script, that allign Billboard planes to the camera can be find here.

Tricks

Some times it is necessary to use colors brighter than 255. The only way to do it is to use the texture multiplier and the "Acolor" texture type. ...

Michas Todo list ;o) - thin paper (SSS and Acolor trick)

- update metal material: Is a grey diffuse layer necessary to get better result with GI without "reflect"?

- glass and "double sided" ?

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