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r300g: Fix provoking vertex for non-quads.

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Read the comments. In short, we can't possibly pass piglit's
glean/clipFlat without some help from Gallium and an API/spec change.
This commit is contained in:
Corbin Simpson
2009-12-18 21:50:45 -08:00
parent f13a904c34
commit 759fd1f25f
1 changed files with 25 additions and 6 deletions
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src/gallium/drivers/r300/r300_render.c
+25 -6
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@@ -83,15 +83,34 @@ static uint32_t r300_provoking_vertex_fixes(struct r300_context *r300,
/* By default (see r300_state.c:r300_create_rs_state) color_control is
* initialized to provoking the first vertex.
*
* If we are provoking the first vertex, then there's a quirk in the
* specification for ARB_provoking_vertex that essentially makes the
* second vertex the correct one to provoke for triangle fans.
* Triangle fans must be reduced to the second vertex, not the first, in
* Gallium flatshade-first mode, as per the GL spec.
* (http://www.opengl.org/registry/specs/ARB/provoking_vertex.txt)
* Otherwise, force the last vertex, as GL standard. */
*
* Quads never provoke correctly in flatshade-first mode. The first
* vertex is never considered as provoking, so only the second, third,
* and fourth vertices can be selected, and both "third" and "last" modes
* select the fourth vertex. This is probably due to D3D lacking quads.
*
* Similarly, polygons reduce to the first, not the last, vertex, when in
* "last" mode, and all other modes start from the second vertex.
*
* ~ C.
*/
if (r300->rs_state->rs.flatshade_first) {
if (mode == PIPE_PRIM_TRIANGLE_FAN) {
color_control |= R300_GA_COLOR_CONTROL_PROVOKING_VERTEX_SECOND;
switch (mode) {
case PIPE_PRIM_TRIANGLE_FAN:
color_control |= R300_GA_COLOR_CONTROL_PROVOKING_VERTEX_SECOND;
break;
case PIPE_PRIM_QUADS:
case PIPE_PRIM_QUAD_STRIP:
case PIPE_PRIM_POLYGON:
color_control |= R300_GA_COLOR_CONTROL_PROVOKING_VERTEX_LAST;
break;
default:
color_control |= R300_GA_COLOR_CONTROL_PROVOKING_VERTEX_FIRST;
break;
}
} else {
color_control |= R300_GA_COLOR_CONTROL_PROVOKING_VERTEX_LAST;