Mesa (master): r300g: Fix provoking vertex for non-quads.
Corbin Simpson
csimpson at kemper.freedesktop.org
Sat Dec 19 05:54:31 UTC 2009
Module: Mesa
Branch: master
Commit: 759fd1f25f33273e0b7c02598bfa5b97d1a82d77
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=759fd1f25f33273e0b7c02598bfa5b97d1a82d77
Author: Corbin Simpson <MostAwesomeDude at gmail.com>
Date: Fri Dec 18 21:50:45 2009 -0800
r300g: Fix provoking vertex for non-quads.
Read the comments. In short, we can't possibly pass piglit's
glean/clipFlat without some help from Gallium and an API/spec change.
---
src/gallium/drivers/r300/r300_render.c | 31 +++++++++++++++++++++++++------
1 files changed, 25 insertions(+), 6 deletions(-)
diff --git a/src/gallium/drivers/r300/r300_render.c b/src/gallium/drivers/r300/r300_render.c
index 11c7ce8..2d70ec2 100644
--- a/src/gallium/drivers/r300/r300_render.c
+++ b/src/gallium/drivers/r300/r300_render.c
@@ -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;
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