> This puzzles me. I'm not disputing you're wrong - usually there's some 
> option to set the number of subsamples taken - but since a GPU can *only* 
> draw straight lines, you'd think they could just use the closed-form 
> formulas for doing mathematically perfect AA on polygon edges. It takes 
> about 3 float-ops. No subsamples required.

That method has problems when you are drawing triangles adjacent to each 
other.  Also how does your method work with a pixel shader?  With 
multi-sampling type AA it's easy because the scene is just rendered at a 
higher resolution and then scaled down, this automatically fixes issues with 
adjacent triangles and calculating pixel colours.

> That's what I heard. I also hear that only about 0.1% of the stuff Pixar 
> does actually involves any ray tracing, with is kind of unbelievable...

Probably only very few surfaces actually *need* raytracing, the rest can be 
scanline rendered.

> I still find it rather hard to believe that you can take a complex shape 
> such as the surface of a water splash and automatically tesselate it.

If you're going for physical accuracy then your simulation data will be in 
voxels or something anyway, so using marching cubes or similar will get you 
your tesselated mesh directly.  If you just want an artistic look (and are a 
skilled enough artist) then draw a rough mesh by hand and use some form of 
sub-divison to smooth it.

Also:

http://graphics.pixar.com/library/Whitewater/paper.pdf

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