Hi, On Monday, September 15, 2014 18:11:51 Roland Scheidegger wrote: > btw I'm not entirely sure everything is really correct with llvmpipe wrt > that extension (the rasterization stuff, gallium isn't involved in the > texture conversion). There's some very annoying differences how things > work between d3d10 and GL there (I suspect there's actually bugs wrt > d3d10 too especially when outputting depth from the pixel shader but so > far we got away with it). > So, with old style GL rendering, you can't actually produce depth values > outside 0/1, due to clipping. But this is no longer true since a while > for various reasons - fragment shader writing depth, ARB_depth_clamp, > clip control... There's various places such values are clamped later - > with ARB_depth_clamp if enabled they are clamped to min/max depth range > (hence not outside 0/1 unless using the nv extension), I'm pretty sure > there's also a 0/1 clamp elsewhere if you output depth from a fragment > shader. > With d3d10, you can likewise disable clipping, but there's no 0/1 clamp > anywhere in sight (just to value range reproducible by depth buffer > format), and the depth clamp is always enabled, regardless any depth > clip enable / disable bits (clamping to the zmin/max range, which is not > limited). > In any case, I think there's a lot of possiblities of subtle bugs when > trying to support this extension.
Hmm, I tend to agree with what you are saying. Anyway, I am after the behavior of a projection matrix ranging from close to far away, providing a decent depth precision. Using the trick described in the earlier reference and shown in the piglit test does this. The nice thing is that a huge range of today available drivers out in the wild support this trick without any performance impact. So, if I had an alternative there with the same properties, I would have never tried this. ... and still, I you know an alternative, that I just do not see/know, tell me! Greetings Mathias _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
