This fixes issues where polygons that should be culled (due to negative
w, for instance) may not be.
Signed-off-by: Alyssa Rosenzweig <aly...@rosenzweig.io>
---
src/gallium/drivers/panfrost/midgard/midgard_compile.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/src/gallium/drivers/panfrost/midgard/midgard_compile.c
b/src/gallium/drivers/panfrost/midgard/midgard_compile.c
index 6b6a405d963..cd8412c2dff 100644
--- a/src/gallium/drivers/panfrost/midgard/midgard_compile.c
+++ b/src/gallium/drivers/panfrost/midgard/midgard_compile.c
@@ -2919,13 +2919,15 @@ write_transformed_position(nir_builder *b, nir_src
input_point_src, int uniform_
/* gl_Position will be written out in screenspace xyz, with w set to
* the reciprocal we computed earlier. The transformed w component is
- * then used for perspective-correct varying interpolation */
+ * then used for perspective-correct varying interpolation. The
+ * transformed w component must preserve its original sign; this is
+ * used in depth clipping computations */
nir_ssa_def *screen_space = nir_vec4(b,
nir_channel(b, viewport_xy, 0),
nir_channel(b, viewport_xy, 1),
screen_depth,
- nir_fabs(b, w_recip));
+ w_recip);
/* Finally, write out the transformed values to the varying */
--
2.20.1
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