ILM Presentation

David Lenihan

January 15th, 2007

Who Am I?

David LenihanDallas, TexasSoftware EngineerLove all things related to 3D graphicsAttend SIGGRAPH every year for past 10

years

Who Am I?

9+ years developing flight simulator software Real-time (<16 ms per frame) C++ OpenGL Shading Languages: Cg & GLSL Windows, Linux, IRIX, and Solaris Plug-ins for Maya Qt Toolkit for cross-platform tools

Who Am I?

3D Modeling Purchased Maya Complete for $2,000 (ouch) to

learn about modeling and animation Want to understand the whole 3D pipeline, not just

the runtime side 2 Years Experience with Maya A programmer that knows how to model

Modeling “War”

Currently in a modeling “war” with some friends Idea: pick something to model and post your

progress and findings to a blog Goal: learn more about how to model Antagonize each other via comments on blogs

that aren’t updating enough so we don’t lose interest in the “war”

Modeling “War”

Building Bank of America Plaza Tallest/most distinct building in Dallas 72 stories

Wanted to use geometry for details, not texture/photos In flight simulators, a building is usually a cube with

texture. Easy/Quick to create Renders fast

Why? Looks good at any zoom level Photos have incorrect lighting for dynamic environments

Modeling “War”

Modeling “War”

Window Frame was my first completed component Geometry-only No Texture Single default material

Modeling “War”

Modeling “War”

My model looks “flat”Why didn’t my model look as “cool” as the

models I see in tutorials?

Modeling “War”

Modeling “War”

Found It! Article in Game Developer Magazine “Ambient Occlusion and You”, by Ryan Ellis August 2006

Audience Background

Use Maya?Use Ambient Occlusion?

Why Ambient Occlusion is Interesting

Unique, non-photorealistic look Great for showing off geometric detail Fast (compared to Global Illumination) Several uses

Dirt/Rust Shader Ambient light pass when compositing an image

Easy to understand how it works Becoming mainstream. Supported in:

Autodesk Maya 6.5+ Autodesk Max 7+ Google SketchUp Hash Animation:Master Etc.

Ambient Occlusion in Flight Sims

Surprised to find none of our real-time modelers knew about Ambient Occlusion

Why? Real-time modeling (Creator) only supports OpenGL

hardware accelerated lighting (per vertex/Gouruad) Use a single light source (Sun or Moon) No Shadows Speed (<16 ms) more important than image quality Draw everything in one pass

What is Ambient Occlusion?

A bit like telling Ben Franklin about how electricity works… ILM invented Ambient Occlusion! Presented at SIGGRAPH 2002 (San Antonio) course by ILM’s

Hayden Landis “Production Ready Global Illumination” http://www.debevec.org/HDRI2004/landis-S2002-course16-prodread

yGI.pdf

Ambient Occlusion is how much ambient light a surface will likely receive White indicates maximum ambient light (no occlusion) Black indicates no ambient light (fully occluded)

Also known as “Sky Light”

How Does It Work?

For every visible point… Shoot rays randomly

out (TotalRays) Count the number of

rays that do not intersect with an object (NumMisses)

Set point color == NumMisses/TotalRays

How to Do Ambient Occlusion in Maya

Start with the window I built

How to Do Ambient Occlusion in Maya

Render with Maya Software for reference

How to Do Ambient Occlusion in Maya

Create Mental Ray Ambient Occlusion Texture in HyperShade

How to Do Ambient Occlusion in Maya

Middle Mouse drag texture to window Connect texture “OutValue” to

initialShadingGroup “SurfaceShader”

How to Do Ambient Occlusion in Maya

Let’s see what it looks like…render with “Mental Ray”

How to Do Ambient Occlusion in Maya

Looks grainy…fix it! Increase number of samples from 64 to 256

How to Do Ambient Occlusion in Maya

Re-render!

How to Do Ambient Occlusion in Maya

Done! Compare Maya Software render to Mental Ray

Ambient Occlusion Render

References

http://en.wikipedia.org/wiki/Ambient_occlusion http://www-viz.tamu.edu/students/bmoyer/617/a

mbocc/ http://www.debevec.org/HDRI2004/landis-S2002

-course16-prodreadyGI.pdf “Ambient Occlusion and You”, Ryan Ellis, Game

Developer Magazine, August 2006 Autodesk Maya 8.0 Online Help

The End

Thanks for listening!