From 475548f6c93f2b32c1a397c59be4ed17935d6b42 Mon Sep 17 00:00:00 2001 From: Brian Paul Date: Sat, 16 Feb 2013 11:54:22 -0700 Subject: draw: fix non-perspective interpolation in interp() This fixes a regression from ab74fee5e1a3fc3323b7238278637b232c2d0d95. When we use the clip coordinate to compute the screen-space interpolation factor, we need to first apply the divide-by-W step to the clip coordinate. Fixes http://bugs.freedesktop.org/show_bug.cgi?id=60938 Note: This is a candidate for the 9.1 branch. (cherry picked from commit 5da967aff5adb3e27954488206fb885ea1ede0fd) --- src/gallium/auxiliary/draw/draw_pipe_clip.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/src/gallium/auxiliary/draw/draw_pipe_clip.c b/src/gallium/auxiliary/draw/draw_pipe_clip.c index 7b879c4cd50..3110809ce0e 100644 --- a/src/gallium/auxiliary/draw/draw_pipe_clip.c +++ b/src/gallium/auxiliary/draw/draw_pipe_clip.c @@ -167,12 +167,17 @@ static void interp( const struct clip_stage *clip, { int k; t_nopersp = t; - for (k = 0; k < 2; k++) + /* find either in.x != out.x or in.y != out.y */ + for (k = 0; k < 2; k++) { if (in->clip[k] != out->clip[k]) { - t_nopersp = (dst->clip[k] - out->clip[k]) / - (in->clip[k] - out->clip[k]); + /* do divide by W, then compute linear interpolation factor */ + float in_coord = in->clip[k] / in->clip[3]; + float out_coord = out->clip[k] / out->clip[3]; + float dst_coord = dst->clip[k] / dst->clip[3]; + t_nopersp = (dst_coord - out_coord) / (in_coord - out_coord); break; } + } } /* Other attributes -- cgit v1.2.3