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mesa: restore and fix Keith's "further degenerate the special case lit substitute"

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There was a bug in emit_degenerate_lit() that caused the SLT to produce
unpredictable results in lit.z

Plus, added a bunch of new comments.
This commit is contained in:
Brian Paul 2008-06-12 11:17:20 -06:00
parent 23d340c9ed
commit 5ecb2f2d0f
1 changed files with 32 additions and 14 deletions
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46
src/mesa/main/ffvertex_prog.c
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@ -969,25 +969,29 @@ static struct ureg calculate_light_attenuation( struct tnl_program *p,
}
/**
* Compute:
* lit.y = MAX(0, dots.x)
* lit.z = SLT(0, dots.x)
*/
static void emit_degenerate_lit( struct tnl_program *p,
struct ureg lit,
struct ureg dots )
{
struct ureg id = get_identity_param(p);
/* 1, 0, 0, 1
*/
emit_op1(p, OPCODE_MOV, lit, 0, swizzle(id, Z, X, X, Z));
struct ureg id = get_identity_param(p); /* id = {0,0,0,1} */
/* 1, MAX2(in[0], 0), 0, 1
/* Note that lit.x & lit.w will not be examined. Note also that
* dots.xyzw == dots.xxxx.
*/
emit_op2(p, OPCODE_MAX, lit, WRITEMASK_Y, lit, swizzle1(dots, X));
/* 1, MAX2(in[0], 0), (in[0] > 0 ? 1 : 0), 1
/* MAX lit, id, dots;
*/
emit_op2(p, OPCODE_SLT, lit, WRITEMASK_Z,
lit, /* 0 */
swizzle1(dots, X)); /* in[0] */
emit_op2(p, OPCODE_MAX, lit, WRITEMASK_XYZW, id, dots);
/* result[2] = (in > 0 ? 1 : 0)
* SLT lit.z, id.z, dots; # lit.z = (0 < dots.z) ? 1 : 0
*/
emit_op2(p, OPCODE_SLT, lit, WRITEMASK_Z, swizzle1(id,Z), dots);
}
@ -1007,6 +1011,14 @@ static void build_lighting( struct tnl_program *p )
struct ureg _bfc0 = undef, _bfc1 = undef;
GLuint i;
/*
* NOTE:
* dot.x = dot(normal, VPpli)
* dot.y = dot(normal, halfAngle)
* dot.z = back.shininess
* dot.w = front.shininess
*/
for (i = 0; i < MAX_LIGHTS; i++)
if (p->state->unit[i].light_enabled)
nr_lights++;
@ -1144,10 +1156,13 @@ static void build_lighting( struct tnl_program *p )
/* Calculate dot products:
*/
emit_op2(p, OPCODE_DP3, dots, WRITEMASK_X, normal, VPpli);
if (!p->state->material_shininess_is_zero)
if (p->state->material_shininess_is_zero) {
emit_op2(p, OPCODE_DP3, dots, 0, normal, VPpli);
}
else {
emit_op2(p, OPCODE_DP3, dots, WRITEMASK_X, normal, VPpli);
emit_op2(p, OPCODE_DP3, dots, WRITEMASK_Y, normal, half);
}
/* Front face lighting:
*/
@ -1181,15 +1196,18 @@ static void build_lighting( struct tnl_program *p )
if (!is_undef(att)) {
/* light is attenuated by distance */
emit_op1(p, OPCODE_LIT, lit, 0, dots);
emit_op2(p, OPCODE_MUL, lit, 0, lit, att);
emit_op3(p, OPCODE_MAD, _col0, 0, swizzle1(lit,X), ambient, _col0);
}
else if (!p->state->material_shininess_is_zero) {
/* there's a non-zero specular term */
emit_op1(p, OPCODE_LIT, lit, 0, dots);
emit_op2(p, OPCODE_ADD, _col0, 0, ambient, _col0);
}
else {
/* no attenutation, no specular */
emit_degenerate_lit(p, lit, dots);
emit_op2(p, OPCODE_ADD, _col0, 0, ambient, _col0);
}