IIRC, all Radeons older than HD 7700 or so can do fixed-function fog, but Gallium doesn't have a proper interface for it. There is no dedicated shader output though, so r300g and r600g use a texcoord slot if there is any left. I think all drivers except softpipe/llvmpipe/svga already do the X001 swizzling.
Considering that the fog varying is being turned into a generic vec4, I wonder why we don't just use TGSI_SEMANTIC_GENERIC for it. Marek On Wed, Nov 20, 2013 at 5:28 PM, Roland Scheidegger <srol...@vmware.com> wrote: > On 11/20/2013 03:23 PM, jfons...@vmware.com wrote: >> >> From: José Fonseca <jfons...@vmware.com> >> >> D3D9 Shader Model 2 restricted the fog register to one component, >> http://msdn.microsoft.com/en-us/library/windows/desktop/bb172945.aspx , >> but that restriction no longer exists in Shader Model 3, and several >> WHCK tests enforce that. >> >> So this change: >> - lifts the single-component restriction TGSI_SEMANTIC_FOG >> from Gallium interface >> - updates the Mesa state tracker to enforce output fog has (f, 0, 0, 1) >> - draw module was updated to leave TGSI_SEMANTIC_FOG output registers >> alone >> >> Several gallium drivers that are going out of their way to clear >> TGSI_SEMANTIC_FOG components could be simplified in the future. >> >> Thanks to Si Chen and Michal Krol for identifying the problem. >> >> Testing done: piglit fogcoord-*.vpfp tests >> --- >> src/gallium/auxiliary/draw/draw_llvm.c | 6 ------ >> src/gallium/auxiliary/draw/draw_vs_exec.c | 7 +------ >> src/gallium/docs/source/tgsi.rst | 10 +++------- >> src/mesa/state_tracker/st_glsl_to_tgsi.cpp | 7 +++++++ >> src/mesa/state_tracker/st_mesa_to_tgsi.c | 7 +++++++ >> 5 files changed, 18 insertions(+), 19 deletions(-) >> >> diff --git a/src/gallium/auxiliary/draw/draw_llvm.c >> b/src/gallium/auxiliary/draw/draw_llvm.c >> index fe49b86..71cc45f 100644 >> --- a/src/gallium/auxiliary/draw/draw_llvm.c >> +++ b/src/gallium/auxiliary/draw/draw_llvm.c >> @@ -659,12 +659,6 @@ generate_vs(struct draw_llvm_variant *variant, >> LLVMBuildStore(builder, out, >> outputs[attrib][chan]); >> } >> break; >> - case TGSI_SEMANTIC_FOG: >> - if (chan == 1 || chan == 2) >> - LLVMBuildStore(builder, bld.zero, >> outputs[attrib][chan]); >> - else if (chan == 3) >> - LLVMBuildStore(builder, bld.one, >> outputs[attrib][chan]); >> - break; >> } >> } >> } >> diff --git a/src/gallium/auxiliary/draw/draw_vs_exec.c >> b/src/gallium/auxiliary/draw/draw_vs_exec.c >> index 6100394..83cc5fd 100644 >> --- a/src/gallium/auxiliary/draw/draw_vs_exec.c >> +++ b/src/gallium/auxiliary/draw/draw_vs_exec.c >> @@ -167,12 +167,7 @@ vs_exec_run_linear( struct draw_vertex_shader >> *shader, >> output[slot][2] = >> CLAMP(machine->Outputs[slot].xyzw[2].f[j], 0.0f, 1.0f); >> output[slot][3] = >> CLAMP(machine->Outputs[slot].xyzw[3].f[j], 0.0f, 1.0f); >> } >> - else if (name == TGSI_SEMANTIC_FOG) { >> - output[slot][0] = machine->Outputs[slot].xyzw[0].f[j]; >> - output[slot][1] = 0; >> - output[slot][2] = 0; >> - output[slot][3] = 1; >> - } else >> + else >> { >> output[slot][0] = machine->Outputs[slot].xyzw[0].f[j]; >> output[slot][1] = machine->Outputs[slot].xyzw[1].f[j]; >> diff --git a/src/gallium/docs/source/tgsi.rst >> b/src/gallium/docs/source/tgsi.rst >> index f80c08d..1070619 100644 >> --- a/src/gallium/docs/source/tgsi.rst >> +++ b/src/gallium/docs/source/tgsi.rst >> @@ -2420,13 +2420,9 @@ TGSI_SEMANTIC_FOG >> >> Vertex shader inputs and outputs and fragment shader inputs may be >> labeled with TGSI_SEMANTIC_FOG to indicate that the register contains >> -a fog coordinate in the form (F, 0, 0, 1). Typically, the fragment >> -shader will use the fog coordinate to compute a fog blend factor which >> -is used to blend the normal fragment color with a constant fog color. >> - >> -Only the first component matters when writing from the vertex shader; >> -the driver will ensure that the coordinate is in this format when used >> -as a fragment shader input. >> +a fog coordinate. Typically, the fragment shader will use the fog >> coordinate >> +to compute a fog blend factor which is used to blend the normal fragment >> color >> +with a constant fog color. > > Maybe add some text that the "fog coord" really is just an ordinary vec4 reg > like regular semantics? > > > >> >> >> TGSI_SEMANTIC_PSIZE >> diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp >> b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp >> index 6319079..74b3e5b 100644 >> --- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp >> +++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp >> @@ -4889,6 +4889,13 @@ st_translate_program( >> t->outputs[i] = ureg_DECL_output(ureg, >> outputSemanticName[i], >> outputSemanticIndex[i]); >> + if (outputSemanticName[i] == TGSI_SEMANTIC_FOG) { >> + /* force register to contain a fog coordinate in the form (F, >> 0, 0, 1). */ >> + ureg_MOV(ureg, >> + ureg_writemask(t->outputs[i], TGSI_WRITEMASK_XYZW & >> ~TGSI_WRITEMASK_X), >> + ureg_imm4f(ureg, 0.0f, 0.0f, 0.0f, 1.0f)); >> + t->outputs[i] = ureg_writemask(t->outputs[i], >> TGSI_WRITEMASK_X); >> + } >> } >> if (passthrough_edgeflags) >> emit_edgeflags(t); >> diff --git a/src/mesa/state_tracker/st_mesa_to_tgsi.c >> b/src/mesa/state_tracker/st_mesa_to_tgsi.c >> index 921b0f9..7d79c62 100644 >> --- a/src/mesa/state_tracker/st_mesa_to_tgsi.c >> +++ b/src/mesa/state_tracker/st_mesa_to_tgsi.c >> @@ -1121,6 +1121,13 @@ st_translate_mesa_program( >> t->outputs[i] = ureg_DECL_output( ureg, >> outputSemanticName[i], >> outputSemanticIndex[i] ); >> + if (outputSemanticName[i] == TGSI_SEMANTIC_FOG) { >> + /* force register to contain a fog coordinate in the form (F, >> 0, 0, 1). */ >> + ureg_MOV(ureg, >> + ureg_writemask(t->outputs[i], TGSI_WRITEMASK_XYZW & >> ~TGSI_WRITEMASK_X), >> + ureg_imm4f(ureg, 0.0f, 0.0f, 0.0f, 1.0f)); >> + t->outputs[i] = ureg_writemask(t->outputs[i], >> TGSI_WRITEMASK_X); >> + } >> } >> if (passthrough_edgeflags) >> emit_edgeflags( t, program ); >> > > Otherwise looks good to me. Can't say I'm a big fan of our half-baked > d3d10-bolted-on-d3d9 semantics style, but this just changes a weirdo > semantic into one which doesn't really have much meaning which is fine by me > - I think you get lucky because there aren't any drivers which can't > actually do this, even r300 which can't do SM3 looks like it treats fog > interpolation like any other generic semantic (though that was just a very > quick glance). > > Roland > > _______________________________________________ > mesa-dev mailing list > mesa-dev@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/mesa-dev _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
