The Powder Toy can have shaders through deco. Somethings look better with shaders, and some look better without shaders. We should keep the option of wether we can see shaders or not.

compute shaders are good for things like transparency, volume, dyntex, etc(Blender Cycles,for example).

not so much for logic, i.e. which particle is next to another. that's a job for the CPU.

the reason some tasks are faster on a GPU is because the unit is more focused on those tasks, and indeed can't perform just any general task. CPUs appear slower only because they're trying to do a broad selection of tasks.

I'd recommend using OpenCL over DirectX as the game is multiplatform and DirectX is specific to Windows. Also, wouldn't you be using DirectCompute, not DirectX?

zBuilder:

compute shaders are good for things like transparency, volume, dyntex, etc(Blender Cycles,for example).

not so much for logic, i.e. which particle is next to another. that's a job for the CPU.

the reason some tasks are faster on a GPU is because the unit is more focused on those tasks, and indeed can't perform just any general task. CPUs appear slower only because they're trying to do a broad selection of tasks.

 Anything that is massively parallelized is good for the GPU. Especially physics computations. GPUs are faster than CPUs in physics calculations by large orders of magnitude.