[Mesa-dev] [PATCH 3/8] anv: Fix near plane clipping on Gen7/7.5.

[Kenneth Graunke]

The Gen7/7.5 clip code used APIMODE_OGL, while the Gen8+ clip code used
APIMODE_D3D.  The meaning hasn't changed, so one of these must be wrong.

It appears that the hardware documentation is completely wrong.  It
claims that the "API Mode" bit means:

   0h    APIMODE_OGL    NEAR_VP boundary == 0.0 (NDC)
   1h    APIMODE_D3D    NEAR_VP boundary == -1.0 (NDC)

However, DirectX typically uses 0.0 for the near plane, while unextended
OpenGL uses -1.0.  i965's gen6_clip_state.c uses APIMODE_D3D for the
GL_ZERO_TO_ONE case, so I believe the meanings are backwards from what
the documentation says.

Section 23.2 ("Primitive Clipping") of the Vulkan 1.0.21 specification
contains the following equations:

   -w_c <= x_c <= w_c
   -w_c <= y_c <= w_c
      0 <= z_c <= w_c

This means that Vulkan follows D3D semantics.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/intel/vulkan/gen7_pipeline.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/intel/vulkan/gen7_pipeline.c b/src/intel/vulkan/gen7_pipeline.c
index 01c04f3..a50d9c7 100644
--- a/src/intel/vulkan/gen7_pipeline.c
+++ b/src/intel/vulkan/gen7_pipeline.c
@@ -124,7 +124,7 @@ genX(graphics_pipeline_create)(
       clip.FrontWinding             = vk_to_gen_front_face[rs_info->frontFace],
       clip.CullMode                 = vk_to_gen_cullmode[rs_info->cullMode],
       clip.ClipEnable               = !(extra && extra->use_rectlist),
-      clip.APIMode                  = APIMODE_OGL,
+      clip.APIMode                  = APIMODE_D3D,
       clip.ViewportXYClipTestEnable = true,
       clip.ViewportZClipTestEnable  = !pipeline->depth_clamp_enable,
       clip.ClipMode                 = CLIPMODE_NORMAL,
-- 
2.9.0