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authorBrian Paul <brian.paul@tungstengraphics.com>2008-02-29 11:37:12 -0700
committerBrian Paul <brian.paul@tungstengraphics.com>2008-02-29 11:37:12 -0700
commit2a121e8e2289d2ca136f511c5a6ef049f9c99ec4 (patch)
tree8fd77e4b02c95222bb1a034ddbaf03c73a863303
parent0b47eb4808aa47e2ab276ab60493e28774cef21a (diff)
gallium: tweak coords for wide lines
-rw-r--r--src/gallium/auxiliary/draw/draw_wide_line.c21
1 files changed, 12 insertions, 9 deletions
diff --git a/src/gallium/auxiliary/draw/draw_wide_line.c b/src/gallium/auxiliary/draw/draw_wide_line.c
index 946a983f00..9a168ce8bd 100644
--- a/src/gallium/auxiliary/draw/draw_wide_line.c
+++ b/src/gallium/auxiliary/draw/draw_wide_line.c
@@ -86,7 +86,10 @@ static void wideline_line( struct draw_stage *stage,
const float dx = FABSF(pos0[0] - pos2[0]);
const float dy = FABSF(pos0[1] - pos2[1]);
-
+
+ /* small tweak to meet GL specification */
+ const float bias = 0.125f;
+
/*
* Draw wide line as a quad (two tris) by "stretching" the line along
* X or Y.
@@ -95,10 +98,10 @@ static void wideline_line( struct draw_stage *stage,
if (dx > dy) {
/* x-major line */
- pos0[1] = pos0[1] - half_width - 0.25f;
- pos1[1] = pos1[1] + half_width - 0.25f;
- pos2[1] = pos2[1] - half_width - 0.25f;
- pos3[1] = pos3[1] + half_width - 0.25f;
+ pos0[1] = pos0[1] - half_width - bias;
+ pos1[1] = pos1[1] + half_width - bias;
+ pos2[1] = pos2[1] - half_width - bias;
+ pos3[1] = pos3[1] + half_width - bias;
if (pos0[0] < pos2[0]) {
/* left to right line */
pos0[0] -= 0.5f;
@@ -116,10 +119,10 @@ static void wideline_line( struct draw_stage *stage,
}
else {
/* y-major line */
- pos0[0] = pos0[0] - half_width + 0.25f;
- pos1[0] = pos1[0] + half_width + 0.25f;
- pos2[0] = pos2[0] - half_width + 0.25f;
- pos3[0] = pos3[0] + half_width + 0.25f;
+ pos0[0] = pos0[0] - half_width + bias;
+ pos1[0] = pos1[0] + half_width + bias;
+ pos2[0] = pos2[0] - half_width + bias;
+ pos3[0] = pos3[0] + half_width + bias;
if (pos0[1] < pos2[1]) {
/* top to bottom line */
pos0[1] -= 0.5f;