How does a GPU work [40 mn of reading - published 5/18/2006 11:25:30 PM - Target : Débutant]

Author

Thibault MICHEL Student-Engineer Supinfo Paris SUPINFO graduate year  2010    Write to the person    All projects of the same author    Mini-CV of the author

4 - the pixel pipeline

Just like the vertex pipeline, the operation of the pixel pipeline is complicated, but can be summarised as follows: in entry it receives pixels with their information and respective data, and at exit it returns an operational pixel. The analogy with the vertex pipeline does not stop there, since the pixel pipeline is declined in two versions: fixed and programmable; and similarly, the fixed version existed previously on the older graphics boards.

Let us quickly see the specificities of each version. First the fixed version, whose action is mainly at the level of textures. The fixed pixel pipeline will use the coordinates of the pixel, and apply them to achieve the desired texture. Note also the role of “the mixer of textures”, also assured. The programmable pixel pipeline can also be compared to the other pipeline present in the GPU, except that this time  in entry there will be a pixel and information; then several actions, whose order is not preset, will act to form a final complete pixel. Note that the pixel pipeline is also called the “pixel shader”.

About performance, note that the deceleration occurs at this stage of treatment of the pixels; therefore, the more numerous the pixel pipelines in the GPU, the higher the performance (for your information, the top-of-the-range chart at the time of the drafting of the project has 48 pixels pipelines).