RenderWonk

Whew! I’m back from SIGGRAPH, which was exciting and exhausting (as it usually is). I got a few days behind in the rush; I’ll finish up the remaining items of note in this post (in the order I saw them, not necessarily in order of importance).

• Wave Particles: this is a technique for simulating 2D waves which has some limitations (fixed wave speed, limited boundary shapes) but is very fast, low on memory and GPU-friendly. Basically wave fronts are represented as a series of stateless deterministic particles. Wave-object interactions are supported.
• Shrek Lighting: most film CG lighting used to be done via placement of lots of small direct lights rather than via global illumination (GI), but many film houses are making the transition to GI-based lighting. PDI is one notable example - in the transition from Shrek to Shrek 2 they moved to (single-bounce) global illumination for their lighting and never looked back. In two different presentations at SIGGRAPH they mentioned this transition as a good thing for them. Some games still do their prelighting with a multitude of direct lights, and it does afford the lighting artists a lot of control, but I think this approach will become rarer as time goes on.
• Stencil Routed A-Buffer: This sketch presented a way to get order independent transparency faster than depth peeling; in effect abusing the MSAA samples as A-buffer fragments. The method is clever but has some drawbacks (not the least of which is the loss of MSAA when using it).
• Advanced Real-Time Rendering in 3D Graphics and Games: This full-day course was excellent, featuring many great tips from premier game developers like Valve and Crytek. Unfortunately the course notes are not up yet, but hopefully they wil be up soon at the AMD conference presentation webpage (or perhaps at the old ATI one). Of particular note were Valve’s improvements to their famous but unfortunately named ‘Radiosity Normal Maps’, and Crytek’s ‘Screen-Space Ambient Occlusion’ method.
• LucasArts & ILM: A Course in Film and Game Convergence: this tutorial outlines LucasArt’s and ILM’s attempt at greater collaboration between the two companies. I’m intrigued by the relationship between film and game rendering, so this tutorial was of particular interest to me. It seems that overall the experience was positive (LucasArts sure got some great tools out of the deal!) and it will be interesting to see how it develops in future.
• Real-Time Edge-Aware Image Processing with the Bilateral Grid: This paper presented a clever data structure for doing bilateral filtering and various other edge-aware processing several orders of magnitude faster than previous methods (though some of that speedup was due to the GPU implementation and not the algorithm itself). These types of filters are usually very slow because they are large and not separable. The numbers they quoted (9ms for a good-sized bilateral filter on a 720p image with a fast GeForce 8000-series card) is almost fast enough for game post-processing effects (the time budget for a post-processing pass is closer to 1-2ms), so it might be worth looking at the description of the implementation in the paper to see if there are any obvious optimization possibilities.