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st/mesa: handle front/back-face +1/-1 vs. 1/0 conversion

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Fixes progs/glsl/twoside.c demo.
This commit is contained in:
Brian Paul 2009-11-30 08:56:47 -07:00
parent a1b9c4e22a
commit 7725744433
1 changed files with 29 additions and 0 deletions
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29
src/mesa/state_tracker/st_mesa_to_tgsi.c
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@ -675,6 +675,31 @@ emit_inverted_wpos( struct st_translate *t,
}
/**
* OpenGL's fragment gl_FrontFace input is 1 for front-facing, 0 for back.
* TGSI uses +1 for front, -1 for back.
* This function converts the TGSI value to the GL value. Simply clamping/
* saturating the value to [0,1] does the job.
*/
static void
emit_face_var( struct st_translate *t,
const struct gl_program *program )
{
struct ureg_program *ureg = t->ureg;
struct ureg_dst face_temp = ureg_DECL_temporary( ureg );
struct ureg_src face_input = t->inputs[t->inputMapping[FRAG_ATTRIB_FACE]];
/* MOV_SAT face_temp, input[face]
*/
face_temp = ureg_saturate( face_temp );
ureg_MOV( ureg, face_temp, face_input );
/* Use face_temp as face input from here on:
*/
t->inputs[t->inputMapping[FRAG_ATTRIB_FACE]] = ureg_src(face_temp);
}
/**
* Translate Mesa program to TGSI format.
* \param program the program to translate
@ -746,6 +771,10 @@ st_translate_mesa_program(
emit_inverted_wpos( t, program );
}
if (program->InputsRead & FRAG_BIT_FACE) {
emit_face_var( t, program );
}
/*
* Declare output attributes.
*/