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video card questions

Discussion in 'Graphics Cards' started by Flamingsupernova, Nov 26, 2007.

  1. Flamingsupernova

    Flamingsupernova New Member

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    Hey guys, I have some questions to ask which may seem pretty standard, but i guess i'll never know if i never ask so this is them.

    what is/are:

    stream processors,

    ROP's,

    Texture address units,

    texture filtering processors

    memory bit-depth,

    memory bandwidth.


    If you can answer even just one ill be very greatful, cheers.
     
  2. DarkMatter New Member

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    I wil try to explain this shortly and then link some articles where this is explained better.

    3D rendering is done by pixel, which means that the whole 3D pipeline is applied to each pixel independently (well kinda). Imagine a window with a grid, what you see through each hole of the grid is a pixel. The renderer first finds what surface has to be rendered through that pixel and find how this surface is lit (vertex stage), which is the color (texture) of the surface in that point and then apply many other effects that whould affect its appearance (pixel stage). All this is done in Shaders. Shaders are predefined programs that make some kind of transformation on the data, so game developers don't have to program from scratch.

    Each of those steps are done in different units within the card.

    - Stream Processors: Before Ati Xenon GPU on XB360 and Nvidia 8800 on the PC (later HD2900 from Ati too) , Vertex related calculations were done on the Vertex pipeline (vertex processors and suplemental circuitry) and Pixels shaders on Pixel processors. Now they are both done on the Streams Processors along with the new DX10 feature, Geometry shader.

    - Texture Address and Mapping Units: this units find and place (map) the required texel(s) (texture element or texture pixel) that belong(s) to the pixel being rendered. (Reason for the plural on texture filtering.)

    - Texture Filtering Units: Most times than not, each pixel won't coincide with one texel. On distant objects more than one pixel on the texture (texel) has to be rendered on the area that represents only one pixel. To resolve this there are many filtering methods (beautifully explained on the links), but it's enough to say that those are performed in these units.

    - ROP (Raster Operation Processor/Pipeline or Render Output Processor): Most of computer generated images (cgi, even real time renderings, such as games) nowadays are rendered with multiple passes. In games, for example, is usual to add a layer in which most non-vertex related effects are added, the so-called Post Processing Effects. The job of ROPs is blend all those layers, commonly called fragments, into a unique pixel to be displayed.

    - Memory bit depth and bandwidth: Both are related. Bit depth is the number of physical interconnects that exists between the GPU and memory, as well as the capacity of the GPU to operate on them. Bandwidth is the multiplication of bit depth and memory speed and represents the maximum rate at wich data can be transported through the bus between GPU and memory.

    Hope this helps you, but I recommend you read these links (specially the first one), since they explain a lot better how rendering is done, with lots of images. It also explains texture filtering methods, antialiasing methods, shadowing methods, but in a very comprehensive way. The next 2 are explanations of how those units are arranged in recent microarchitectures: Nvidia 8800 and DAAMIT HD2900. And there is some bits of interesting info there too.

    The best easy to read explanation to game graphics that I have ever found:

    http://www.crysis-online.com/forum/index.php/topic,8362.0.html

    Architecture previews:

    http://techreport.com/articles.x/11211
    http://techreport.com/articles.x/12458

    A more extensive and highly technical guide. TBH I suggest you to not try going too deep on this one, but maybe you can find puntual info on the table of contents . It has three parts and it's not easy to navigate, though:

    http://www.extremetech.com/article2/0,1697,9722,00.asp

    See you! :toast:
     
    Flamingsupernova says thanks.
  3. Flamingsupernova

    Flamingsupernova New Member

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    Thanks dude, you're a legend
     

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