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The fixed function pipeline??

Started by _Wox_ Mar 30, 2004 at 7:51 AM 4 replies 600+ views
Original Post
_Wox_
_Wox_
I was wondering where the steps in the fixed function pipeline are executed? Which one is exectued on the CPU and which one on the GPU? Below is the list with steps in the pipeline, which of these is run on CPU and which one on GPU? Tesselation World transform Vertex blending View transform Vertex fog Lightning and materials Projection transform Clipping Homogenoeous divide Viewport scaling Triangle setup Sample texture Blend diffuse and specular color Alpha test Depth test Stencil test Per Pixel fog Alpha blend Dither Gamma When using Vertex shaders you can do the world transformation and stuff in the shader...if you not use a shader you do SetTransform(D3DTS_WORLD in the application....is this just a function call to the GPU? Regards Wox
_Wox_
_Wox_
No actually I am not. But I was just wondering if the fixed function pipeline operations were executed on the GPU or CPU. Cuz I guess the fixed function pipeline consists of Pixel Processing, Primitive Processing and Vertex Processing? Here pixel processing and vertex processing can be replaced by pixel and vertex shaders, but primitive processing it that run on the GPU or the CPU?
davepermen
davepermen
depends on hw.

but generally, old gpu''s only do rastericing and pixel plotting stuff, and the ones since gf1 do all. thats why they have a feature called T&L, transform and lighting. means they can handle the full pipeline.

but for the details, it really depends on hw. and doesn''t really mather in the end.



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_Wox_
_Wox_
Ok here is the problem!

I am doing a schoolwork, and then I am about to write a paper about the fixed function pipeline and the programmable pipeline. I know that the programmale pipeline consists of vertex and pixel shaders that is executed on the GPU, i.e. they replaces the pixel and vertex processing sections of the fixed function pipeline.
What I dont know is if you are not using the programmable pipeline but only the fixed. And I am using a new graphics card with all hw support. Then where are the steps in the fixed function pipeline executed, i.e. pixel and vertex processing and the primitive processing? Is that all on the GPU if hw support exists? Or is something still executed on the CPU?
OrangyTang
OrangyTang
The fixed function pipeline can be thought of as a pair of hardwired vertex and pixel shaders, physically implemented by pieces of circuitry on a graphics card. Then when people stared demanding more flexibility the hardwired stuff gradually got replaced by more flexible hardware capable of running these mini programs called vertex and pixel shaders.

In a good graphics card *all* of it gets done in hardware. For older stuff (say, GeForce 1) then you might end up doing the vertex shader on the CPU if its complex, go even older and you''ll find (as dave mentioned) cards that only do the rasterisation and need the CPU to do geometry transformation and lighting (say, Voodoo 1 & 2).

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