Framebuffer content and pixel shaders

Discussion in 'Rendering Technology and APIs' started by Bastion, Jul 27, 2006.

  1. Xmas

    Xmas Porous
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    The problem is that the hardware can process multiple polygons covering the same pixel simultaneously. Thus the shader processing can reach the point where you want to read from the framebuffer before the previous polygon at that pixel has been finished. To give you correct behaviour, the hardware would have to detect these overlap situations and stall the read operation until the previous pixel has finished.

    I don't think you'll have any luck with S3. That functionality is something they advertise, but it isn't exposed anywhere in any public API.
     
  2. Graham

    Graham Hello :-)
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    Is there really anything stopping company X from implementing a programmable blend? This could actually be very useful... A mini shader with just 'dest' and 'src' inputs :) Compacted HDR formats would be the first use that comes to mind. (or does DX10 allow this? - I should look that up I suppose before posting :p)
     
  3. stepz

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    Hardware cost is the main party pooper.
     
  4. nutball

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    IIRC this (frame buffer contents as input to shaders) was also discussed during the development of OpenGL 2.0. It was in the draft spec for some time, but got nixed by the IHVs.
     
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