Zack Rusin pisze: > On Wednesday 09 December 2009 08:44:20 Keith Whitwell wrote: > >> On Wed, 2009-12-09 at 04:41 -0800, michal wrote: >> >>> Zack Rusin pisze: >>> >>>> Hi, >>>> >>>> currently Gallium3d shaders predefine all their inputs/outputs. We've >>>> handled all inputs/outputs the same way. e.g. >>>> VERT >>>> DCL IN[0] >>>> DCL OUT[0], POSITION >>>> DCL OUT[1], COLOR >>>> DCL CONST[0..9] >>>> DCL TEMP[0..3] >>>> or >>>> FRAG >>>> DCL IN[0], COLOR, LINEAR >>>> DCL OUT[0], COLOR >>>> >>>> There are certain inputs/output which don't really follow the typical >>>> rules for inputs/outputs though and we've been imitating those with >>>> extra normal semantics (e.g. front face). >>>> >>>> It all falls apart a bit on anything with shader model 4.x and up. >>>> That's because in there we've got what Microsoft calls system-value >>>> semantics. ( >>>> http://msdn.microsoft.com/en-us/library/ee418355(VS.85).aspx#System_Val >>>> ue ). They all represent system-generated inputs/outputs for shaders. >>>> And while so far we only really had to handle front-face since shader >>>> model 4.x we have to deal with lots of them (geometry shaders, domain >>>> shaders, computer shaders... they all have system generated >>>> inputs/outputs) >>>> >>>> I'm thinking of adding something similar to what D3D does to Gallium3d. >>>> So just adding a new DCL type, e.g. DCL_SV which takes the vector name >>>> and the system-value semantic as its inputs, so >>>> FRAG >>>> DCL IN[0], COLOR, LINEAR >>>> DCL IN[1], COLOR[1], LINEAR >>>> DCL IN[2], FACE, CONSTANT >>>> would become >>>> FRAG >>>> DCL IN[0], COLOR, LINEAR >>>> DCL IN[1], COLOR[1], LINEAR >>>> DCL_SV IN[2], FACE >>>> >>>> It likely could be done in a more generic fashion though. Opinions? >>>> >>> Zack, >>> >>> What would be the difference between >>> >>> DCL IN[2], FACE, CONSTANT >>> >>> and >>> >>> DCL_SV IN[2], FACE >>> >>> then? Maybe the example is bad, but I don't see what DCL_SV would give >>> us the existing DCL doesn't. >>> >> I'd have proposed something slightly different where the SV values don't >> land in the INPUT file but some new register file. >> >> The reason is that when we start looking at geometry shaders, the INPUT >> register file becomes two-dimensional, but these SV values remain >> single-dimensional. That means that for current TGSI we'd have stuff >> like: >> >> DCL IN[0..3][0] POSITION >> DCL IN[0..3][1] COLOR >> DCL IN[2] SOME_SYSTEM_VALUE >> >> Which is pretty nasty - half of the input file is one dimensional, half >> two-dimensional, and you need to look at the index of the first >> dimension to figure out whether the input reg is legal or not. >> >> So, I'm think some new register file to handle these system-generated >> values is one possiblility, as in: >> >> DCL SV[0], FACE >> >> or >> >> DCL SV[1], PRIMITIVE_ID >> >> Thoughts? >> > > Yea, I like that. > > And then separate syntax to handle the properties or overloading DCL? i.e. > DCL GS_INFO PRIM_IN TRIANGLES > vs > PROPERTY GS_INFO PRIM_IN TRIANGLES > ? > I think a geometry shader should have its own GS_INFO token that would convey the information it needs, i.e. no overloading of the DCL token.
GS_INFO PRIM_IN TRIANGLES GS_INFO PRIM_OUT TRIANGLE_STRIP GS_INFO MAX_VERTEX_COUNT 3 /* vertices_out for gl */ ------------------------------------------------------------------------------ Return on Information: Google Enterprise Search pays you back Get the facts. http://p.sf.net/sfu/google-dev2dev _______________________________________________ Mesa3d-dev mailing list Mesa3d-dev@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mesa3d-dev
