There is no question that technology is growing at an unimaginable pace. With the addition of Revit’s 2019 Physically Accurate Materials comes the opportunity to push our renderings to the next level. This whitepaper is designed to take readers on a deep dive of what physically based rendering (PBR) is and how to use the enhanced materials to achieve a photorealistic render. We’ll cover how to create each of the different textures that are needed to develop a physically accurate material and where to apply them inside Revit. We will look at Revit’s cloud rendering service and Enscape to see how they can utilize the PBR materials to enhance our renderings.

What is Physically Based Rendering?

Physically Based Rendering is a way of creating materials that will accurately respond to light just as if they were in the real world. It is a theory based on measured surface values.

What are the benefits?

Physically Based rendering removes the guess work about what materials will look like in a certain lighting condition. We can have comfort in knowing that if we have to make a change to the lighting in our scene the materials will follow along and act how they would in real life.

It requires fewer textures to make a PBR material and thus saving on computing memory.

It will help develop a texturing standard for your company knowing every material that is created will have all of the texture maps that make up a Physically Accurate material.

Physics behind PBR:

How does light work?

To help build our texture materials we should have a basic understanding of how light works and interacts with the materials around us. When a light wave encounters an object, it is either transmitted, reflected, absorbed, refracted, polarized, diffracted or scattered depending on the composition of the object and the wavelength of the light.

Reflection:

Reflection is when incident light (incoming light) hits an object and bounces off. Very smooth surfaces such as mirrors reflect almost all incident light. Most materials have some form of surface roughness that will determine how much light is being reflected.

I N T R O D U C T I O N

P H Y S I C S B E H I N D P B R

Light interacting with a smooth surface

Light interacting with a rough surface

Source: Science ABC

Source: Marmoset

P H Y S I C S B E H I N D P B R

Energy Conservation:

When the light ray meets the surface, some of the light ray is absorbed by the object, the light intensity will decrease as it changes into another form of energy, usually heat. The rest of the light ray is reflected off the object.

Refraction:

Refraction is when the light waves change direction as they pass from one medium to another. Light travels faster in air than it does in water. As light travels into a different medium, the change in speed bends the light. The Index of Refraction (IOR) is used to determine how much the light will be bent when it is traveling from one medium to the next.

Source: Medium

Source: Substance 3D

Source: Substance 3D

P H Y S I C S B E H I N D P B R

Fresnel:

Fresnel is everywhere! The most common place we see it is when looking at water. When we look straight down we can see to the bottom, but when we look at an angle we cannot see to the bottom anymore. This will be rendered when we set the Reflectance Value in our Revit material. The rougher the material such as a rock, the less Fresnel there will be.

Source: Scratchapixel

R E V I T B A S E M A T E R I A L S E X P L A I N E D

Revit comes with a variety of pre-built materials for you to use. The materials with a yellow triangle in the bottom left corner (see image below) will indicate it is a legacy material and are not setup to be physically accurate. Materials that do not have the yellow triangle are setup to be physically accurate. If you wanted to start from scratch with your own materials, Revit has included four base materials. (Five in Revit 2020 Glazing) Found in the Asset Browser > Appearance Library > Base Materials, they have the characteristics of a standard PBR material such as albedo/diffuse, roughness or bump/normal. We will also look at some examples of materials that are already created using these base materials. They have the characteristics of real-world materials already setup. In Revit, values are displayed like this 0.06 which translates to 6 percent.

R E V I T B A S E M A T E R I A L S E X P L A I N E D

The Opaque Material is setup to be used for materials that are non-metallic or transparent. Typical examples of this are: Plastic, wood, stone, ceramics etc. etc.

R E V I T B A S E M A T E R I A L S E X P L A I N E D

The Transparent Material is used for all materials where most of the light rays can pass through the material without any scattering. Types of materials that would normally be used for this are glass, water and acrylic.

R E V I T B A S E M A T E R I A L S E X P L A I N E D

The Metal Material is setup to be used for all Metal materials.

R E V I T B A S E M A T E R I A L S E X P L A I N E D

Layered Material is used to represent materials that have a bottom specular surface and a top clear coat. Typical uses for this material are, carbon fibers panels, metallic paints and surfaces that might have reflective specks like granite and car paint.

R E V I T B A S E M A T E R I A L S E X P L A I N E D

Glazing Material should be used for all glass materials that have a large surface, such as exterior windows.

R E V I T B A S E M A T E R I A L S E X P L A I N E D

Materials Maps:

PBR materials in Revit typically have 2-4 different texture maps per material that define its characteristics. Below are the names of the materials and the descriptions of what they do. Most of the time if you use textures from any of the texture sites provided in this whitepaper, they will have the correct naming standard to them. This will be a good way of knowing where to plug them into Revit.

Albedo:

This Albedo map is the base color of the material. In Revit, this material will go in the Parameters- Image channel. The big difference between the Albedo map and the traditional Diffuse map is the Albedo map has the shadows removed from the texture. This is so our materials will look more natural in every lighting condition.

Roughness:

This controls how the surface imperfections are being displayed. This is an inverted Gloss Map. Black is shiny. White is not shiny. The difference between this map and the traditional Gloss Map is it is simply inverted (white is shiny, black is not.) controls how rough or smooth a material’s surface is. Rough materials scatter reflected light in more directions than smooth materials, which controls how blurry or sharp a reflection is. A roughness of 0 results in a mirror reflection and roughness of 1 result in a diffuse surface.

R E V I T B A S E M A T E R I A L S E X P L A I N E D

Bump/Normal:

New to 2019 and found under the Bump Map tab, we have the option to add a Normal Map. A Normal Map displays dents and bumps on the object and is like the regular Bump Map but much more advanced. With a Bump Map when you are looking straight at the material it will look like there is depth to it. With a Normal Map it will give the material the illusion of being 3D because it has information about bumps and dents in the XYZ axes. This plays a huge factor when we are looking at the model from all different angles.

When using a Normal Map texture, be sure to switch the Data Type from Height Map to Normal Map, otherwise your material will have black spots on it.

R E V I T B A S E M A T E R I A L S E X P L A I N E D

Advanced Highlights:

This is where we can use an Ambient Occlusion (AO) map to simulate the occlusion of dents and cracks or any other surface imperfections.

To help find these materials, I have created a few new material libraries.

These libraries will work for Revit 2019 and 2020. This is just an easier path to the existing materials.

The adsklib file will be pulling the textures from this location: C:\Program Files (x86)\Common Files\Autodesk Shared\Materials\Textures\3\Mats.

You can put these libraries into your My Documents folder or wherever you would like. These materials are already setup utilizing the base materials that we have covered.

In the material browser, click on the open library button and click open existing library.

M A T E R I A L L I B R A R I E S

Select the adsklib file you would like to load.

To find additional materials, go to:

M A T E R I A L L I B R A R I E S

If you do not want to use the default Revit textures, you have two options.

1. Create your own from scratch with photos you have taken or been provided.2. Research various texturing sites and create your own inventory. Links to free texture sites are

included in the resources section.

We will be using Substance Alchemist (Alchemist is my personal favorite texturing tool.) to create our own materials from scratch and create variations of those materials. Alchemist will allow us to create all the material maps we will need for use in Revit and create multiple variations of that texture. Substance was used by Autodesk to create the new Physically Accurate materials in Revit 2019.

There are some other pieces of software that can create the material maps we need as well.

Launch Substance Alchemist and click the Create tab.

In Substance, we can start from scratch or use some of the default materials as a base or we can use a .sbsar file from one of the texture sites we found. To start, click the Create tab. Then load one of the .sbsar files you found.

S U B S T A N C E A L C H E M I S T

We can use the built-in settings to control different aspects of the material to get the exact look.

Another way to create materials with Substance Alchemist is by creating variations of materials from a single image. While still in the create tab, drag and drop an image found on a manufacturer’s site or from your library.

S U B S T A N C E A L C H E M I S T

Now you can start adding layers and customizing your material.

S U B S T A N C E A L C H E M I S T

Once you are happy with your material, you can click Export Current View and choose the textures and file format you want. Remember, Revit will use Albedo/Diffuse, Roughness, Bump/Normal and Ambient Occlusion maps.

S U B S T A N C E A L C H E M I S T

Now that you can create materials, let’s take a look at the results you can get with the new materials inside of Revit’s Cloud Rendering.

Example of legacy Revit Materials:

New Physically Accurate Materials added:

R E V I T ’ S C L O U D R E N D E R I N G

Let’s take a look at how these new materials can enhance your Enscape renders. Using these new materials in conjunction with Enscape will not only improve your still renders but will also improve your real-time experience and your VR experience when showing the client their model. Below is an example of a PBR brick material in Enscape.

E N S C A P E R E N D E R S

Enscape model before new materials:

Enscape model after with new materials:

E N S C A P E R E N D E R S

Utilizing these new materials will allow you to breathe life into the images. It will give you the ability to add character to the scene and help you tell the story of the image which will help the client better understand and connect with their model better.

S O U R C E SHere is a collection of some great resources to find free and paid textures, along with amazing sites to get more information about PBR materials, and how light works:

Texture Sites:

Substance 3D PBR Guide

Marmoset: Physically Based Rendering, and you can too!

Marmoset: Basic Theory of Physically Based Rendering

Chaos Group: Understanding Metalness

Substance 3D: Autodesk Revit: PBR Material Workflow for Architecture

Physically Based Rendering: From Theory to Implementation

About Rendering with Autodesk Raytracer

ScratchaPixel 2.0: Introduction to Shading

3D Textures

Substance 3D: Substance Source

Texture Haven

Poliigon TexturesCC0 TexturesTextures.comCGTraderSubstance ShareC:\Program Files (x86)\Common Files\Autodesk Shared\Materials\Textures\3\Mats

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