Am 15.09.2014 19:04, schrieb Mathias Fröhlich: > > Hi again, > > 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. > > You are actually mentioning clip control. > I knew that there is something in the queue, but I thought that this is > not available as an extension and only available with new enough OpenGL > versions. But there actually is ARB_clip_control. > > This one actually fits the bill. > Am I right that you would not object against ARB_clip_control? I don't have anything against this at all, though I think it's only partly related (and as far as I can tell, issue 8 of ARB_clip_control is totally bogus wrt the changed behavior of GL for depth range, as this was a retroactively fixed spec error). gallium (and the software drivers via draw) should be able to do that already I believe. It won't do anything against the weird fragment shader depth output clamp, for instance. Maybe someone else can provide some more input about this stuff, I bet there were some discussions at some point about 0/1 depth clamps at some point in the ARB/Khronos.
Roland _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
