From cc8afbd3862fedfe42e51c3774960d1c7078ec53 Mon Sep 17 00:00:00 2001 From: Robert Ellison Date: Tue, 24 Mar 2009 09:53:22 -0600 Subject: i965: fix point rasterization when rendering to FBO The FBO pixel coordinate system, with (0,0) as the upper-left pixel, is inverted in Y compared to the normal OpenGL pixel coordinate system, which has (0,0) as its lower-left pixel. Viewport and polygon stipple are sensitive to this inversion; so is point rasterization. The basic fix is simple: when rendering to an FBO, instead of the normal RASTRULE_UPPER_RIGHT that's appropriate for OpenGL windows, use the Y inversion RASTRULE_LOWER_RIGHT. Unfortunately, current Intel documentation has this value listed as "Reserved, but not seen as useful". It does work on at least some i965-class devices, though; and the worst that could happen if an older device didn't support it would be incorrect point rasterization to FBOs, which is what happens already, so this fix is at least no worse than what happens presently, and is better for some (and possibly all) i965-class devices. --- src/mesa/drivers/dri/i965/brw_sf_state.c | 28 +++++++++++++++++++++++++++- 1 file changed, 27 insertions(+), 1 deletion(-) (limited to 'src/mesa/drivers/dri/i965/brw_sf_state.c') diff --git a/src/mesa/drivers/dri/i965/brw_sf_state.c b/src/mesa/drivers/dri/i965/brw_sf_state.c index 93a9686f71..fc4eddda0a 100644 --- a/src/mesa/drivers/dri/i965/brw_sf_state.c +++ b/src/mesa/drivers/dri/i965/brw_sf_state.c @@ -231,7 +231,33 @@ sf_unit_create_from_key(struct brw_context *brw, struct brw_sf_unit_key *key, sf.sf6.line_width = 0; /* _NEW_POINT */ - sf.sf6.point_rast_rule = BRW_RASTRULE_UPPER_RIGHT; /* opengl conventions */ + key->render_to_fbo = brw->intel.ctx.DrawBuffer->Name != 0; + if (!key->render_to_fbo) { + /* Rendering to an OpenGL window */ + sf.sf6.point_rast_rule = BRW_RASTRULE_UPPER_RIGHT; + } + else { + /* If rendering to an FBO, the pixel coordinate system is + * inverted with respect to the normal OpenGL coordinate + * system, so BRW_RASTRULE_LOWER_RIGHT is correct. + * But this value is listed as "Reserved, but not seen as useful" + * in Intel documentation (page 212, "Point Rasterization Rule", + * section 7.4 "SF Pipeline State Summary", of document + * "Intel® 965 Express Chipset Family and Intel® G35 Express + * Chipset Graphics Controller Programmer's Reference Manual, + * Volume 2: 3D/Media", Revision 1.0b as of January 2008, + * available at + * http://intellinuxgraphics.org/documentation.html + * at the time of this writing). + * + * It does work on at least some devices, if not all; + * if devices that don't support it can be identified, + * the likely failure case is that points are rasterized + * incorrectly, which is no worse than occurs without + * the value, so we're using it here. + */ + sf.sf6.point_rast_rule = BRW_RASTRULE_LOWER_RIGHT; + } /* XXX clamp max depends on AA vs. non-AA */ sf.sf7.sprite_point = key->point_sprite; -- cgit v1.2.3