On Thu, Apr 07, 2005 at 01:29:21PM -0400, Adam Jackson wrote: | I would think it possible to decompose the scene along notional view volumes | in the tiler...
In general that doesn't work, because (a) primitives that are clipped based on the raster position clip in their entirety, rather than just clipping the fragments outside the view volume; (b) clipping computations can yield different parameter values at the boundaries than interpolation during rasterization would have yielded, leading to texturing discontinuities or Mach banding. (These can be really dramatic if interpolation isn't perspective-correct.) If interpolation is done in such a way that you can guarantee reasonable correspondence between interpolated and clipped parameter values, you might be able to get away with overlapped view volumes and blending to minimize the seams. I haven't looked at this stuff in years, so someone with more current experience than mine might have a better idea. | I don't know that the rasteriser is the right place to solve this problem. Well, it is true that we don't have any control over the hardware rasterizers, so we can't depend on solving the whole problem there. But I doubt it can be solved without work in the OpenGL implementation. | Eventually X will outgrow the 15-bit coordinate limit, and/or Roland will | want to do 1440dpi on A4 or whatever. So it's not about asking for 12 bits | of fragment precision as opposed to 11, it's about asking for infinite | precision. I don't think it's quite that bad. :-) But you do need to guarantee how parameters are interpolated. And that the OpenGL implementation allows parameters to be specified with enough precision that higher-level libraries can tile the scene, while leaving errors at the seams that are too small to see. (For example, the OpenGL implementation shouldn't represent colors with just 8 bits.) Allen ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click -- _______________________________________________ Dri-devel mailing list Dri-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/dri-devel