i965: interpolate colors with perspective correction by default

...rather than with linear interpolation.  Modern hardware should use
perspective-corrected interpolation for colors (as for texcoords).
glHint(GL_PERSPECTIVE_CORRECTION_HINT, mode) can be used to get
linear interpolation if mode = GL_FASTEST.

1 files changed, 19 insertions, 7 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_wm_fp.c b/src/mesa/drivers/dri/i965/brw_wm_fp.c
index 1798d842c7..5b302cc309 100644
--- a/src/mesa/drivers/dri/i965/brw_wm_fp.c
+++ b/src/mesa/drivers/dri/i965/brw_wm_fp.c
@@ -354,13 +354,25 @@ static void emit_interp( struct brw_wm_compile *c,
 		 src_undef());
       }
       else {
-	 emit_op(c,
-		 WM_LINTERP,
-		 dst,
-		 0,
-		 interp,
-		 deltas,
-		 src_undef());
+         if (c->key.linear_color) {
+            emit_op(c,
+                    WM_LINTERP,
+                    dst,
+                    0,
+                    interp,
+                    deltas,
+                    src_undef());
+         }
+         else {
+            /* perspective-corrected color interpolation */
+            emit_op(c,
+                    WM_PINTERP,
+                    dst,
+                    0,
+                    interp,
+                    deltas,
+                    get_pixel_w(c));
+         }
       }
       break;
    case FRAG_ATTRIB_FOGC: