Thursday, August 14, 2008

Siggraph 08 Wednesday

I attended lots of paper sessions today. The first session I attended was on real-time techniques. There were papers presented on shadow mapping techniques, real-time refraction with caustics, real-time smoke rendering, and meshless hierarchical light transport. The refraction paper created beautiful results but was quite limiting since it used a voxel grid of only 128x128x128 and only had a frame rate between 2 and 7 fps. The smoke paper also had beautiful results for lighting smoke with diffusely convolved cube map. Its limitation was that it required that the smoke be pre-processed so you couldn't dynamically change the smoke. I did find the shadow mapping paper and the light transport paper. I'll probably look into them some more.

Next I attended several sessions hosted by Nvidia. They presented a paper on hair rendering, a paper on terrain rendering and LODing on the GPU, and a discussion of their PhysX system. The hair paper was pretty amazing. The do a real-time simulation on around 160 guide hairs and then instance those to make it appear that there are many 10s of thousands of hairs. Once the verts have been simulated, they're conected with B splines, converted to camera facing triangle strips and rendered using the Kajiya Kay lighting model. The results are really beautiful, but I wonder if the performance requirements are just a but too high for current hardware. The terrain paper was pretty straight forward. Their LOD system basically just reduced the tesselation of the quads based on distance from the camera. They also biased the distance based on the topology of each quad - so if the quad had higher height changes it would be LODed less. They did the same thing for quads that contained a silhouette edge. Pretty good ideas! The PhysX paper was mainly about things to think about when adding physics sims you your projects. I was pretty disappointed that the presentation was so short on actual implementation details.

After the paper session and some lunch, I attended a session on the special effects on Cloverfield and Iron Man. It's always very interesting to see these talks where the special effects artists break down their work on films and talk about how they achieved their results. While it's not directly applicable to my own work, it is very inspiring.

I left the session a little early so that I could attend an appointment with the guys at Image Metrics. They're a company dedicated to facial animation and they do really great work. It was fun to talk with them about their work.

My last paper session of the day was entitled "Many Things." Some guys from Pixar talked about how they created the shaders and textures for all of the robots in Wall-E. They used some really cool material layering techniques blended with geometry specific maps including ambient occlusion, blurred edge maps, up facing maps, and fractal noise patterns. Their material system also allowed them to add specific details like decals. The results were impressive and they were able to create the surfaces for all of the robots in under three months. The second paper in the session was on the foliage system used in Madagascar 2. They did a good job of giving the artist control as well as automating the repetative tasks. The enabled the artists to create a branch and then mark growth source points. Then the user could click on a growth point and the branch would be cloned to that location. Doing this over and over would create the full set of branches for the tree. If I were going to write some software to do trees, I'd probably do it this way. The next paper was on AI driven cars for Speed Racer. The author did lots of work using Massive to create an AI system to drive the cars at over 300 miles an hour around the crazy Speed Racer tracks. The funny thing about this presentation is that the presenter told us that none of his work was actually used in the final movie. Oh well! :) It was pretty cool driving AI anyway. The final presentation was also from Pixar. The presenter explained a method called Brain Springs that allowed them to automate the motion of the robots and imitate physics simulations without actually running any sim at all. This was a very interesting idea to me - translating a character's changed in velocity into automatic secondary movement.

I finished out the day by attending the Computer Animation Festival screenings as well as attending a tribute to Stan Winston. Today was really full! Tomorrow should be great too. I'm looking forward to it.


Blogger Lloyd said...


A few of your textures were just what I needed. Thanks!

Lloyd Travis

August 21, 2008 12:34 AM  
Anonymous Anonymous said...

Thanks so much for posting these textures! they were just what i needed. :)

March 03, 2009 1:53 PM  
Anonymous Anonymous said...

Thanks so much for posting these textures! they were just what i needed. :)

March 03, 2009 1:58 PM  

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