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Exercises for Scientific Visualization with

AVS/ExpressScience & Technology Support Group

High Performance ComputingOhio Supercomputer Center

1224 Kinnear RoadColumbus, OH 43212

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Contents

Project Creation and Download The Network Editor & Data Viewers I The Network Editor & Data Viewers II The Network Editor & Data Viewers III Importing Data I Importing Data II Images and Animations

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Project Creation and Download

In this lab you will download and install the workshop projectfiles

This should only be done once after installation you will haveeverything you need to complete all the other exercises

After this lab you should be familiar with

Starting AVS/Express Saving an AVS/Express project The avsenv file

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Running AVS/Express under Unix

AVS/Express requires that certain environment variables be setbefore it can be run. The most important of these are

LM_LICENSE_FILE Must point to the FLEXlm license file

XP_FEATURE Must be EXPRESS (for the Developers Edition) or VIZ_EXPRESS (for

the Visualization Edition) MACHINE

AVS/Express machine architecture specification ( sgi , sgN32 , ...) LD_LIBRARY_PATH

Should point to the directory lib in the AVS/Express installationdirectory

Ideally this is done automatically by a script (here we usevxp ), which sets these variables and then runs the program

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Running AVS/Express under Windows

For Win9x/NT, the most important environment variables are LM_LICENSE_FILE

Name of the FLEXlm license file (e.g. C:\flexlm\license.dat ) XP_FEATURE

Must be EXPRESS (for the Developers Edition) or VIZ_EXPRESS (forthe Visualization Edition)

MACHINE Should be set to pc

Ideally this is done automatically by a script which sets thesevariables and then runs the program

If you obtain AVS/Express through OSC, a basic script

run_xp.bat is provided

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Creating a Project for this Workshop

Type vxp to run AVS/Express Delete the MultiWindowApp that is created upon startup Note that the current project (visible in the VCP and the top

window bar) is the default project, something like/usr/local/express

Select Project > Save As... Choose a directory name for your project, for example

/home/wrk001/XPtrain AVS/Express will create the directory for you if it doesnt already

exist

Exit AVS/Express (using File > Exit) Change to the project directory Restart AVS/Express to verify that you are in the new project

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The avsenv File

The file avsenv in the project directory indicates the projectsderivation hierarchy

This indicates that the project /tmp/XPtrain is derived fromthe default (read-only) project /usr/local/express64

It is often necessary to modify this file when installing a projectfrom another user, as the directories are not necessarily correct

on your machine This should be the only thing you have to do, assuming all file

references in modules are relative (to the project directory)

gromit$ more avsenv# WARNING: this file is program generated.# Remove these two lines to protect the file from overwrites.XP_PATH=/tmp/XPtrain /usr/local/express64

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Download Class Project Files

The workshop project files are available at

Be sure to unpack the files in the project directory you created Check the avsenv file to see if it is correct; edit if necessary

Restart AVS/Express in the project and verify that the workshoplibraries are visible. There should be three new ones: IAC ,Lectures and Labs

System Format Unpacking command

Unix tar.Z zcat class-prj.tar.Z | tar xvf -

Unix tar.gz gzip -cd class-prj.tar.gz | tar xvf -

Windows zip Use WinZip or unzip class-prj.zip

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The Network Editor & Data Viewers I

In this exercise well load some sample networks and becomefamiliar with the basic data viewer and user interface controls

After this lab you should be familiar with Loading applications Using the module user interfaces Transforming the view

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Start up AVS/Express

Start AVS/Express Find and delete the Multi-window application

A MultiWindowApp comes up by default. This consists of onewindow with many colored user interface icons on its left side, andthe main AVS/Express window which should say AVS/Express aspart of its title bar. In the lower part of the AVS/Express window,also known as the the Application Workspace, you should see asub-window titled MultiWindowApp .

Delete this MultiWindowApp application by right-clicking on its sub-window's title border in the Network Editor, then selecting Deletefrom its pop-up menu.

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Load an Application

Next, read in a sample application Select the Examples library Find the Advect module under the Visualization sub-library. You

may need to first double click the Visualization sub-library in orderto open it.

Left-click on Advect , then drag it down into the applicationworkspace

Advect is a MultiWindowApp , so you will see the network thatcreates this image, the image itself, and the editor panel thatcontains the module UIs in separate windows

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Explore the User Interfaces

Locate the UI for the advector module and experiment withchanging parameters Look in the module stack for the advector module

At the bottom of the UI there is a Run toggle that produces ananimation of the fluid flow

You can also vary the size of the arrows using the Glyph Scaleslider

Examine the UIs for the other modules in the network

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Transformations

Next, experiment with the transformation buttons Rotate, scale, and translate the object Note the behavior of Reset, Normalize and Center Set the object spinning and then toggle between Hardware and

Software rendering. See if there is any difference in renderingspeed.

To spin the object, rotate it and release the mouse button while themouse is still moving

Try turning on perspective Explore other sample visualizations, for example

Surf_plot PolarGraph (in the Graph_Macros sub-library)

Orthoslice TextGlyph

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Create a New Sing l eWindowApp

Start AVS/Express Delete the MultiWindowApp that starts by default Create a new SingleWindowApp

Select File > New Application... Choose a Single-window data viewer with a 3D viewer type If you wish, set the Single-window application with 3D viewer as

the projects default application

The new application begins with a single object instanced theviewer

Study the object libraries. Most of the useful modules are inMain , Accessories and Standard Objects

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Using the Object Finder

In the example network we will build here, we wish to visualizethe electron density in a particular hydrogen atom orbital. Wewill take a slice through the atom and observe differing electrondensities throughout the atom. This and the next few slides willcover the steps needed to find appropriate modules, connectthem together to form a complete network, and save thenetwork to disk.

When selecting modules for a network, you can either scrollthrough the sub-libraries until you locate the correct one, oralternatively you can use the Object Finder to search for aspecific module.

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Using the Object Finder

To use the Object Finder, chooseObject > Find in All Libraries The finder dialog box appears Type the name of the object you

are looking for in the search boxand click on Find

Use the wildcard * to match anycharacters

surf_ matches only this string surf_* matches anything that

begins with surf_

To highlight the location of themodule in the network editorlibrary, click on Show

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Instantiate Modules

Find the Read_Volume module, which is located in the Data_IOlibrary. This module reads a volume format file and converts it toa 3D AVS/Express field.

Instantiate a Read_Volume object by dragging it into theapplication workspace

Instantiate a slice_plane object (located in the Mappers sub-library). This module extracts a 2D slice from a 3D field with anarbitrarily positioned slice plane.

Instantiate a bounds object (located in Mappers as well). Thisgenerates a bounding box around a 3D field.

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Create Data References (Connections)

Connect the modules together as shown:

Check the object Info (use the pop-up menu on each object) tosee what sorts of data the various ports refer to Practice disconnecting modules too

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Read in a Data File

The user interface for Read_Volume contains a file browser To access the UIs, select Editors > Modules and then use the pulldown list (the module stack) to select the module of interest

Click on Browse Navigate to the AVS/Express install directory

Probably /usr/local/express under Unix Often C:\Express under Windows

Continue down to the subdirectory data/volume Select the file hydrogen.dat Click on Okay

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View Completed Application

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The Network Editor & Data Viewers III

In this exercise you will explore additional techniques of the AVS/Express Network Editor and Data Viewer, including Modifying Data Viewer Object Properties Using Multiple Scenes Manipulating Objects Individually Alternate Object Rendering

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Modifying Object Properties Load the application CubeCyl.v

Use File > Load Application... The V file is located in the data subdirectory of the class project

Experiment with transforming the display Make the cube copper colored

The color of the object is one of its properties. Go into the Data

Viewer's Object Editor to access it The user interface for the object's color is under Properties (still in

the Object Editor), General Type Values that approximate copper for the three color dials are:

Hue 0.06, Saturation 0.80, Value 0.60

Note that the option menu in the upper-left corner of the panelshould indicate Object, not Alternate

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Modifying Object Properties

Next, make the cube surface look like real copper by adjustingits surface properties Select Type > Surface in the Object Editor Experiment with different values for Metal, Diffuse, Specular and

other sliders

Next change the background color This is a property of the view , not an object, so invoke the View

Editor , General . See if you can set the color dials to producepurple.

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Using Multiple Scenes

To add a 2D scene, go to the Scene page of the View Editor Specify "2D" as the camera type and "New objects" as the

Object Mode, then click on the Create button. This creates anew scene in the SingleWindowApp . Once the scene is created,look at the Uviewer3D object in the Network Editor. A secondinput port has been added. This is the port for the 2D camera.

Next, add a glyph to the new scene Instance Main.Geometries.Arrow2 and connect it into the new 2D

input port of the Uviewer3D.

Now you can switch scenes between the cube and the arrow Use the radio buttons in the Windows pull-down menu (of the Data

Viewer) to switch between scenes.

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Alternate Object Rendering

Taking advantage of the alternate object capabilities of AVS/Express is a powerful technique for speeding up itsrendering performance during object transformations, especiallyif you have a scene with a huge number of polygonal objects.

Load the application CubeCyl.v

Make sure the cube is the selected object Enable alternate object rendering

Check Alternate Object Enable in the Editors/Object/General panel

Now you can modify the alternate objects properties

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Alternate Object Rendering For example, to make it a wire frame mesh:

Select Modes (under Editors/Object) Use the Edit option menu at the top of this panel to specify

Alternate This indicates that the values you set on this Modes panel apply to the

alternate object for the cube (since it is the selected object), not to thecube itself.

Set Line Rendering to Regular Set Bounds Rendering to None

To make the wire frame mesh green: Specify Alternate using the option menu in the upper-left of the

Editors/Object/Properties panel. Make sure the Type menu is set to General, then adjust the color

dials. To produce green, set: Hue = 0.33, Saturation = 1.00, Value = 1.00

Try rotating the cube. Do you see the green wire frame?

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Interact with the Application

Experiment with the view transformations Access the UI for slice_plane and try changing the parameters

there Clicking on Plane Transform Editor brings up a panel with sliders

that allow you to change the plane position and orientation The distance slider moves the plane in a direction normal to itself

Try opening the slice_plane module directly in the NetworkEditor Edit the parameters directly by opening sub-objects and entering

the new value(s)

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Save the Application

Networks can be saved as an application that can be read backin at a later time, perhaps in a subsequent AVS/Expresssession. The files are stored in ASCII format, and use the Vlanguage.

To save the application Highlight the title bar of your network's application workspace by

left-clicking on it. This selects the network to be saved. Select File > Save Application Its convenient (but not necessary) to save the file in the v

subdirectory of the project Give the file a name (should end in .v )

Examine the resulting V file with your favorite text editor

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Delete and Load the Application

To delete the application from the Network Editor, highlight thetitle bar of your network's application workspace by left-clickingon it. This selects the network to be deleted. Then either Select File > Delete Application... Right-click on the title bar of the application and choose Delete

from the pop-up menu

To re-load the application, select File > Load Application Use the file browser to select the V file you saved previously

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Additional Things to Try

Delete individual objects in the application workspace using thepop-up menu Rename some objects Access object Info and Help

Note that Info shows the object template (i.e. its type) even afterit has been renamed

Note that in Info/Help the ports are listed with the leftmost port atthe top and the rightmost at the bottom

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Another Application

In this exercise you will build a network to read and displayimage files Begin by creating a new application (either Single- or Multi-

window) with a 2D viewer Build the network:

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View Image Files

Use the Read_Image UI to load several image files Set the image format to avs.x With the file browser, navigate to

/Express_install_dir/data/image Select an image file to read

Can you figure out what downsize and crop are doing? Try

changing some of the parameters in their UIs to find out. (Youcan also consult Help for these modules, of course!)

Save the application, delete it from the Network Editor, and readit back in

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Importing Data I

In this lab you will practice some techniques for importing datainto AVS/Express. Topics include: Basic mesh creation Using a saved object to read data Using the Add File Import Module tool

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Non-Cartesian Field

Well begin by creating a 2D field expressed in cylindricalcoordinates: Instance an Accessories.Field_Schema.Field_Cyl_Unif object in

an application with a 3D Data Viewer The Field_Schema modules are basically pre-packaged Field objects

of various kinds

Using the pop-up menu (accessed by right-clicking on the object),open the Object Editor Set nspace = 3 Set ndim = 2

We thus create a 2D mesh that lives in 3 space dimensions Set dims = {5, 16}

This is a uniform mesh, so we need only specify the number of pointsin each dimension and the low and high values of each. This specifies5 points in radius and 16 points in theta.

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Non-Cartesian Field

Set points = { {1, 0, 0}, {5, 3.14159, 0} } The ( radius , theta , z ) values for the endpoints of the mesh Set nnode_data = 1

The number of node_data items at each node Set node_data[0].veclen = 1

The vector length of the node_data item. A value of 1 indicates a

scalar value. Note that you must open the node_data sub-object toaccess this and the following variable Set node_data[0].values = 1.0

Note that AVS/Express fills out the array of values for youautomatically

Note also that the reference operator is used implicitly here when youenter 1.0, i.e. the Object Editor sets the value in the field to => 1.rather than = 1.. Using the reference, the array will automaticallyadjust its size if the dimension (here 5*16 = 80) were to change.Using the assignment, its size would forever be fixed to 80.

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Non-Cartesian Field

Add an output port to theField_Cyl_Unif object Either use the Object Editor,

or select Add Output Port inthe pop-up menu

Finally, render the field Create the network shown

Using the View Editor, see ifyou can make your image looklike this Hint: See the previous lab in

which we set up a wire framealternate object

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Non-Cartesian Field

Next we will create a 3D field expressed in cylindricalcoordinates Instance a new Field_Cyl_Unif and set these values:

nspace = 3 ndim = 3 dims = {5, 16, 10}

points = { {1, 0, 0}, {5, 3.14159, 10} } // {radius, theta, z} nnode_data = 1 node_data[0].veclen = 1 node_data[0] values = 1.0 (Base type: float)

Render the field as before

You might experiment with both external_faces and Accessories.Graphics.Modules.DataObject

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Non-Cartesian Field

Try to make your image look something like this:

For extra credit, create a 3D field expressed in sphericalcoordinates (see Accessories.Field_Schema.Field_Spher_Unif )

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Using a Saved Object to Read Data

In this part of the lab, you'll use an object already designed andsaved to a V file on disk. You can read this object into a libraryworkspace, then use it to read a data file into an AVS/Expressnetwork.

Begin by selecting an editable library Select Library Workspaces from the Libraries pull down menu,

then highlight Workspace 1 by single left-clicking on its title bar.Newly created module templates will be placed into this highlightedlibrary.

Next, select Object > Load Objects and load the Read_Dataobject. It is defined in the file Read_Data.v which is in the

data subdirectory The object template is now available in this library and you cancreate instances of it in the usual way

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Next, construct the following network (create an application witha 3D viewer). Read in the file DataFile.dat which is also inthe project data directory.

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The image should look something like this:

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Open the Read_Data module using the Object Editor. Examinethe objects defined within the module and make sure youunderstand what it is doing. Refer to the layout of the data file.

Remove the leading space character before the first "2" in thefile. Save the file and re-read it. What happens? Make thenecessary corrections in the Read_Data module to keep theapplication working correctly. Try making some other changes.

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Change the data: Create a data_math object and insert it into the network as shown.Be sure to connect the combine_mesh_data output to the first twoports of data_math :

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The data_math module allows you to perform mathematicaloperations on the data in a field. Check Help for this object tosee how it works.

Set some expression, for example sin(#2*#1)*(#1*#2) , inthe data_math module and observe its effect

Finally, add some glyphs (geometric shapes) at the nodes of themesh Instance a glyph object and a Box object

glyph attaches a shape to each node in a field; Box is the actualgeometric object

Note that glyph takes two inputs: a field and a glyph (a shape).Connect the field output of data_math and the output of Box to theappropriate glyph input ports. The red output port contains therenderable image of the boxes; connect this to the viewer.

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Experiment with the Box objects transformation editorto set its scale, as well as theglyph objects scale parameter(see the UIs for these objects)

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Using Add File Import Module

In this exercise you will build a module to read the filesplash.asc located in the data directory of your class project.This is a an ASCII file consisting of 100x100 floating pointnumbers with the following layout:

The file begins with the number of elements in the X and Ydirections, nx and ny, followed by nx*ny rows, each with threecolumns: i j data .

100 100

1 1 -69.011552 1 -66.26960: : :: : :100 100 -49.37508

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Using Add File Import Module Generally, before you invoke the Add File Import Module tool to

describe your file format, you select module(s) appropriate forprocessing the data later on in the network. In this case, wewant to create a 2D (computational space is 2 dimensional) 2-space (2 physical dimensions) uniform scalar field. Then we'llmap it into three dimensions by scaling it in the Z direction

according to the data values. An good module to create the fieldis Accessories.Field_Mappers.uniform_scalar_field , which takesas input a dimensions array and a data array. From there, theresult can be sent to Main.mappers.surf_plot , which will map itinto three dimensions, and then to a viewer. Here your maintask with the Add File Import Module will be to create thedimensions and data arrays for use by the uniform_scalar_field module.

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Using Add File Import Module Select an editable library to hold the new module, for example

Library_Workspaces.Workspace_1 Select Library Workspaces from the Libraries pull down menu,

then highlight one of those workspaces (such as Workspace 1 ) bysingle left-clicking on its title bar.

Select Object > Add File Import Module

Note that if this option is grayed out it most likely means you havenot selected an editable library to hold the module

You will be presented with a dialog sequence to describe thedata layout to AVS/Express. Look again at the structure of thedata file splash.asc

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Using Add File Import Module We will need two File Variables:

dims[2] An array of ints to hold the X and Y dimensions

data[prod(dims)] An array of floats to hold the data values

Note that we do not need to read the coordinate values (i j);

since we are using a uniform field AVS/Express will constructthese for us

We could use an offset variable to skip the first line whenreading the data values, but in this case it is easy to determinethe offset by hand. There are 8 characters from the start of the

file to the first line of data, so the offset is 8 (bytes). Dont forget the (invisible) newline at the end of the first line!

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Using Add File Import Module For dims[] , set

base type int , Object is an array, dimensions [2], variablestored as ASCII, data type int , offset 0 (since the dims start atbeginning of file), number columns in file 2, and check Column #0and Column #1.

For data[] , set

base type float , Object is an array, dimensions [prod(dims)],variable stored as ASCII, data type float , offset 8 (since the dataarray columns start after 8 characters of the file), number columnsin file 3, and check Column #2.

Note the ability to use built-in functions [e.g. prod(dims) ] in Vcommands

When you are finished, the template for the new moduleappears in the library you selected

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Using Add File Import Module You can use the VCP to verify that the reader is working

correctly Create a new application Instance a Splash_Reader Use the file browser in the module UI to load splash.asc In the VCP, drill down to the reader object Use the V commands $list , $get_array and $sub_array to

check the contents of the arrays

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Now use the new reader. Create a new application with a 3Dviewer, and construct the following network. Read insplash.asc using the file browser in the Read_Splash UI.

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Before leaving this lab, save the reader you have built. You cando this in two different ways: Select Project > Save . This saves the current project environment

including the new module you have added. When you restart AVS/Express in this project, Splash_Reader will be immediatelyavailable in the library.

Highlight Splash_Reader in the library workspace and selectObject > Save Objects.... This saves the object template in a Vfile. In this case, when you re-start AVS/Express in the currentproject the module will not appear immediately; it must be re-loaded into an editable library before it can be used.

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Using Add File Import Module In this exercise, you will visualize scattered (unstructured) data

representing concentration. There is one data value per gridpoint, with a 1D array of data points which are randomlyscattered in 3D space.

The data is stored in the ASCII file conc.dat (again in theworkshop data subdirectory) which has a simple columnformat:

The first entry is the number of data points; the subsequentcolumns contain the x, y, z coordinates of a node and the datavalue at that point

100018.37 5.00 10.00 .0618.94 5.00 10.00 .07: : : :

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Using Add File Import Module Here you can use point_mesh to create the unstructured mesh.

This requires as input an array coords[nnodes][nspace]containing the node coordinates.

To create scalar node data you can use the node_scalar module, which takes as input a single array data[nnodes] .

You should then combine the mesh and data into a field usingcombine_mesh_data

A convenient way to attach a sphere to each node, with radiusand/or color set according to the data value at that point is touse the module BubbleViz

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Importing Data II In this lab you will practice some further techniques for importing

data into AVS/Express. Topics include: Using AVS/Express Field Files Using the Read_Column_File module

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Using AVS Field Files The AVS Field file format is useful when you have binary or

ASCII data in a file that can be described by a simple header. AVS/Express provides a module called Read_Field that readsfiles stored in this format.

Examine some sample field files, for example helens1.fld (a 2D, 2-space uniform field)

hydrogen.fld (a 3D uniform field with data in byte format)both of which are in /AVS_install_dir/data/field

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Using AVS Field Files Create a field file to describe the data in splash.asc:

This data consists of the number of elements in the X and Ydirections, nx and ny, followed by nx*ny rows, each with threecolumns: i j data .

It corresponds to a 2D, 2-space uniform scalar (one data itemper node) field

100 1001 1 -69.011552 1 -66.26960: : :: : :100 100 -49.37508

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Using AVS Field Files Once the header file is created, build an application that reads

the file and displays a surface plot based on the data values

If you are having trouble with the header, check the solutionsplash.fld in the data sub-directory

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3D Field File Lobster X-Ray Data In this part of the lab you'll create a field file to look at a volume

data set representing uniformly spaced 3D imaging data The data is located in the file lobster.dat in the class project

data directory It is a binary data file (byte format) The mesh is uniform with ndim=3 and nspace=3

The mesh dimensions are dim1=120 x dim2=120 x dim3=34 It is a scalar (veclen=1) field The first three bytes of the file are the dimensions, the rest is the

data

Create a suitable field header lobster.fld for this data file Use the Read_Field , bounds and isovolume modules to

visualize the data

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3D Field File Lobster X-Ray Data

If you have trouble creating the field file, see the solutionlobster.fld in the workshop data directory

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Read_Column_Fi le

In this lab you will use the Read_Column_File module to readdata in a simple columnar format

We will be working with the files AIR_Quality.data anddata1 in the training data directory

Begin by creating a new application (with a 3D viewer) andinstancing a Read_Column_File object

Examine the data in the file data1 There are 32 rows and 4 columns. The first three integers of each

row are the coordinates of the data value. The last value on eachrow is the data value.

The data is uniform, so we will use table_to_uniform_field to

create the field object

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Read_Column_Fi le

Construct the following network:

In the Read_Column_File UI, set up the columns. When youare finished, click the Read File button at the bottom of the UI.

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Read_Column_Fi le

Before proceeding, disable execution by clicking on the interruptexecution button in the SingleWindowApp This button controls whether the modules in your network

(including the data viewer window's contents) are active. When it isred, none of the modules in your network will execute. Also, allviewer window operations are turned off you can not rotate,transform, or otherwise manipulate the image interactively.

Execution toggle

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Read_Column_Fi le

Set up the parameters fortable_to_uniform_field Columns 0, 1 and 2 are the

axes X, Y and Z,respectively. Column 3 isthe data.

Click on the execution toggleto re-enable execution Adjust parameters in the

other modules, in particularisosurface , solid_contour ,and orthoslice

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Images and Animations In this lab you will explore techniques for creating and exporting

AVS/Express visualizations in several image and animationformats. Topics include: Exporting Images Exporting PostScript Exporting VRML The Loop Module Keyframe Animation with animator Saving Movies with Image_Capture Time Series Field Files Particle Animation

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Exporting Images It is easy to generate 2D images for collaborations and web

pages using AVS/Express. Here you'll experiment with theOutputImage module

Create the network

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Exporting Images Read the file hydrogen.fld (in

/AVS_install_dir/data/field )

Save the view to an image file From the OutputImage UI, select a

file format (GIF or JPEG is good)

Use the file browser to set afilename

Check that the flip toggle is not set(this will flip the image upsidedown)

Click on Write File to output the

image Verify the image file using a vieweror web browser

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PostScript Output It's also easy to generate high-quality vector PostScript images

of your AVS/Express visualizations. Here you'll experiment withthe OutputVPS module, using a network almost identical to theone you have already built.

In the previous network, substitute the OutputVPS module forOutputImage

Check the OutputVPS UI for useful options Save the output to a PostScript file Verify the postscript using xpsview (SGI). How is the image

quality?

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Exporting VRML Virtual Reality Modeling Language , or VRML, is

a way to share 3D content on the web. In thispart of the exercise, you'll experiment withexporting an AVS/Express visualization in theVRML file format. In general, VRML filesgenerated from AVS/Express tend to be very

large. However, if you can keep yourvisualization content reasonably small, you canachieve acceptable performance within a VRMLbrowser.

Build the network shown, and read in the file

water.fld (in /AVS_install_dir/data/field )

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Exporting VRML Set the isosurface parameter to a

low value like 0.01 Export the view to a VRML file

Using the OutputVRML UI, outputexpress.wrl to a temporarydirectory

Use the VRML 1 protocol If your web browser supports VRML,

use it to open express.wrl . Howdoes the performance and imagequality compare to the rendering in

AVS/Express?

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The L o o p Module The Loop module outputs a sequence of integers/floats to drive

downstream modules, such as slicers, isosurface, data filereaders, and image writer modules. By looping over a sequenceof values, an animation is created.

Build the network

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The L o o p Module Read in hydrogen.fld (in

/AVS_install_dir/data/field/ ) Add an input port for the iso_level

parameter, a sub-object of isosurface Open the isosurface module Right-click on the input port for iso_level (on

the left side of the object) Select Export Port from the pop-up menu

Clear the current value for iso_level Open the iso_level object Backspace over its contents Close iso_level and isosurface

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The L o o p Module Connect the Loop module to isosurface as shown:

Set the Loop parameters. For this application choose Start Value = 0 End Value = 255 Increment = 10

Click on Run to see the application cycle through a set ofiso_level values

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Keyframe Animation AVS/Express supports keyframe animation with its animator

module. To create a keyframe animation, you create a series ofviews, the "keyframes" that define known points in the animationyou want to produce. The animator then adds frames betweenthe keyframes to produce an animated sequence. These newframes are created by interpolating parameters of the view, such

as size, position, or color, from one keyframe to the next. Whenyou run the animation, the animator creates frames between thekeyframes by interpolating parameter values to produce thenumber of frames per second you specify for the animation. Theinterpolated frames provide a smooth animation between thefixed points in the animation sequence defined by keyframes.

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Keyframe Animation Build the network:

Note that the animator module is not (visually) connected to any

other module Read in /AVS_install_dir/data/geom/face-sm.geo Reset the view (use the Reset/Normalize/Center button) and

turn off Auto-Normalize If you change a parameter that affects the extents of the data or

the position of the camera, the camera automatically performs areset/normalize/center operation. Making these changes avoidsunexpected shifts in the position of objects in the view as your animation runs.

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Keyframe Animation It is usually convenient to put the animator UI in a separate

window (click the Separate Window toggle) Create some keyframes

First, re-initialize the animation parameters. Click the Reinitializebutton to reset the values of animation parameters in yournetwork to the current values of the parameters in the view. Thisallows you to capture a predictable first keyframe. Note that youcan only use this button before you begin to add keyframes.

Click the Add keyframe button to make the currently displayedview a keyframe. The first keyframe is added at time step 0, and a0 appears in the list of Frame Times in the keyframe control panel.

To add additional keyframes, make the changes needed in theviewing image, then click on the Add keyframe button again. Trychanging different values between keyframes for example,change the color of the face, its position, its size or its surfaceproperties. Add several more frames.

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Keyframe Animation If you are creating a cyclic animation, that is one that ends with the

same image it begins with, you can use the Complete button .When you click on this, animator adds a keyframe that is a copy ofthe first keyframe to the animation sequence.

To delete individual keyframes, select the time of the frame in theFrame Times list and click the Delete Keyframe button . Todelete all the currently defined keyframes, click the Clear button

You can play the animation back using the playback controls:

These controls are similar to VCR buttons.

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Creating Movies with Image_Capture However you choose to generate the sequence of images for

animation, the image_capture module can be used to capturethe frames and assemble the movie. You can save the imageframes to memory or to disk, play them back to any

AVS/Express view or frame buffer, and generate AVI or MPEG-1 movies from them.

Add an i mage_capture object to the previous network:

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Creating Movies with Image_Capture The image_capture UI provides the controls for capturing

images and generating movies To begin capturing images, set the Mode to Capture from View .

Note that as soon as you set the mode to something other thanInactive , the module begins recording an image each time it isre-rendered (i.e. each time the view updates).

You can set the Capture Mode option to specify how the imagesare saved Memory saves the images to your computer's memory (be careful

if there are many frames!) Disk saves the images to temporary files in the directory specified

in the Movie Name box

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Creating Movies with Image_Capture Go back to the animator module and replay your keyframe

animation. As the view is updated, the frames are saved byimage_capture Make sure that nothing occludes the viewer window during this

process! Other windows, the mouse pointer, etc., will appear inthe captured frames if they overlay the viewer window at all.

Play back the frames Set Mode to Playback to View Use the VCR buttons to review the animation

Finally, create the movie file Set Mode to Inactive Select MPEG-1 or AVI format

Choose a movie file name Click on Generate Movie

Check the movie file by viewing it in a browser

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Time Series Field Files The AVS/Express Read_Field module supports time series field

files. These are field files that have information about multipletime steps or frames

Examine /AVS_installation_dir/data/field/m1.fld Field file structure is familiar Note the nstep keyword, indicating the number of time steps

contained in the file Each time step begins with time value = ... and ends with EOT

Construct the network

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Time Series Field Files Read in /AVS_installation_dir/

data/field/m1.fld Note that the Read_Field UI now

contains some additional controlsrelating to time information

Experiment with StepForward /Backward , One-time ,Continuous and Bounce

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Particle Animation Given a vector field, the module Particle_Advector can be used

to animate massless particle flow along the field Useful for visualizing e.g. fluid flows, but can be used with any

vector field

Instantiate Examples.Viz Macros.Particle_Advector Animate the particles

Use the Run toggle at the bottom of the Particle_Advector UI Experiment with the various parameters to see their effects on the

visualization

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