[Mesa-dev] [PATCH] gallium: Make TGSI_SEMANTIC_FOG register four-component wide.
Marek Olšák
maraeo at gmail.com
Wed Nov 20 08:41:51 PST 2013
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 <sroland at vmware.com> wrote:
> On 11/20/2013 03:23 PM, jfonseca at vmware.com wrote:
>>
>> From: José Fonseca <jfonseca at 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
>
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