Neat stuff.
Does anyone know if Canon cameras have GPU chips
The canon firmware doesn't do anything that would require a GPU, so it's safe to assume they don't have one. Digic is a custom chip, there's no way they'd waste die space on something they had absolutely no use for.
They do have a DSP chip which must be capable of some very fast parallel operations, but we don't have any control of that. Whether you could abuse this for 3d is unclear.
If you are willing to do hand optimized ASM, you should be able to do quite fast software 3d (compared to naive C code), ARM946es has quite a few features that the compiler won't readily take advantage of. Also keep in mind there's no FPU, so integer math will be much better.
(edit from the year 2021: Digic 6 and later cams do have a GPU)
