Yes you could in theory use pixel shaders for per pixel 2d effects. I've used glsl many times for just such a thing, but is it realistically something most people here have the knowledge to do? I'd say a big fat no going on the lack of cool looking demos.
But that said, pixel shaders can't replicate routines that require access to main memory. Only modern vertex shader3.0 can read textures, let alone main memory.
There's fundemental difference in approach. Shaders are in out by design. A streaming protocol almost. Where as cpu based 2d is entirely up to the coder to design. It can read main memory, it can access arrays. and most importantly you can write to main memory for feedback.
It's not like the ps3 where you can send vram to and from the cpu easy as you like with shaders. If it were then well, i'd be happy and there'd be no need to blitz2dish.
But that said, pixel shaders can't replicate routines that require access to main memory. Only modern vertex shader3.0 can read textures, let alone main memory.
There's fundemental difference in approach. Shaders are in out by design. A streaming protocol almost. Where as cpu based 2d is entirely up to the coder to design. It can read main memory, it can access arrays. and most importantly you can write to main memory for feedback.
It's not like the ps3 where you can send vram to and from the cpu easy as you like with shaders. If it were then well, i'd be happy and there'd be no need to blitz2dish.