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Thread: NVidia: MAX_VERTEX_TEXTURE_IMAGE_UNITS_ARB == 4

  1. #1
    Junior Member Regular Contributor
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    NVidia: MAX_VERTEX_TEXTURE_IMAGE_UNITS_ARB == 4

    NV 56.55 returns 4 for MAX_VERTEX_TEXTURE_IMAGE_UNITS_ARB on my GF 5900 XT. But if I try to use a texture sampler in an ARB_vertex_shader program, I get a compiler error about missing support for texture lookups in vertex shaders. Is this due to the beta status of the GLslang support in the drivers? Will there be support for texture lookups in vertex shaders even on GF 5x00 level hardware in the future?

  2. #2
    Senior Member OpenGL Guru
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    Re: NVidia: MAX_VERTEX_TEXTURE_IMAGE_UNITS_ARB == 4

    It's odd that they would return 4 for that number. However, if they were planning/writing/debugging a software compiled vertex shader, then they could easily support 4 units. And, of course, if their next hardware supports 4 too, it would make the transition from software to hardware trivial.

    My guess is that they intend to support 4 vertex texture image units, but haven't gotten the software compiler decent enough to actually put it in as a beta release.

    And definately, NV30 (5200+) does not support vertex texture lookups in hardware. But, as we've seen in the past, software vertex shaders, especially on modern processors, aren't entirely slow either.

  3. #3
    Member Regular Contributor
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    Re: NVidia: MAX_VERTEX_TEXTURE_IMAGE_UNITS_ARB == 4

    Yes, I think it is because of Beta Status. Early ATI implementations had the same problem
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