From 759fd1f25f33273e0b7c02598bfa5b97d1a82d77 Mon Sep 17 00:00:00 2001 From: Corbin Simpson Date: Fri, 18 Dec 2009 21:50:45 -0800 Subject: 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 file changed, 25 insertions(+), 6 deletions(-) (limited to 'src/gallium') diff --git a/src/gallium/drivers/r300/r300_render.c b/src/gallium/drivers/r300/r300_render.c index 11c7ce859db..2d70ec2ac94 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; -- cgit v1.2.3