diff --git a/piet-gpu/shader/build.ninja b/piet-gpu/shader/build.ninja
index 448caf2..7b80f6f 100644
--- a/piet-gpu/shader/build.ninja
+++ b/piet-gpu/shader/build.ninja
@@ -119,6 +119,6 @@ build gen/draw_leaf.hlsl: hlsl gen/draw_leaf.spv
 build gen/draw_leaf.dxil: dxil gen/draw_leaf.hlsl
 build gen/draw_leaf.msl: msl gen/draw_leaf.spv
 
-build spv: phony gen/backdrop_lg.spv gen/backdrop.spv gen/bbox_clear.spv gen/binning.spv gen/coarse.spv gen/draw_leaf.spv gen/draw_reduce.spv gen/draw_root.spv gen/kernel4.spv gen/path_coarse.spv gen/pathseg.spv gen/pathtag_reduce.spv gen/pathtag_root.spv gen/tile_alloc.spv gen/transform_leaf.spv gen/transform_reduce.spv gen/transform_root.spv
-build dxil: phony gen/backdrop.hlsl gen/backdrop_lg.hlsl gen/bbox_clear.hlsl gen/binning.hlsl gen/coarse.hlsl gen/draw_leaf.hlsl gen/draw_reduce.hlsl gen/draw_root.hlsl gen/kernel4.hlsl gen/path_coarse.hlsl gen/pathseg.hlsl gen/pathtag_reduce.hlsl gen/pathtag_root.hlsl gen/tile_alloc.hlsl gen/transform_leaf.hlsl gen/transform_reduce.hlsl gen/transform_root.hlsl
-build msl: phony gen/backdrop_lg.msl gen/backdrop.msl gen/bbox_clear.msl gen/binning.msl gen/coarse.msl gen/draw_leaf.msl gen/draw_reduce.msl gen/draw_root.msl gen/kernel4.msl gen/path_coarse.msl gen/pathseg.msl gen/pathtag_reduce.msl gen/pathtag_root.msl gen/tile_alloc.msl gen/transform_leaf.msl gen/transform_reduce.msl gen/transform_root.msl
+build spv: phony gen/backdrop_lg.spv gen/backdrop.spv gen/bbox_clear.spv gen/binning.spv gen/coarse.spv gen/draw_leaf.spv gen/draw_reduce.spv gen/draw_root.spv gen/kernel4.spv gen/kernel4_gray.spv gen/path_coarse.spv gen/pathseg.spv gen/pathtag_reduce.spv gen/pathtag_root.spv gen/tile_alloc.spv gen/transform_leaf.spv gen/transform_reduce.spv gen/transform_root.spv
+build dxil: phony gen/backdrop.hlsl gen/backdrop_lg.hlsl gen/bbox_clear.hlsl gen/binning.hlsl gen/coarse.hlsl gen/draw_leaf.hlsl gen/draw_reduce.hlsl gen/draw_root.hlsl gen/kernel4.hlsl gen/kernel4_gray.hlsl gen/path_coarse.hlsl gen/pathseg.hlsl gen/pathtag_reduce.hlsl gen/pathtag_root.hlsl gen/tile_alloc.hlsl gen/transform_leaf.hlsl gen/transform_reduce.hlsl gen/transform_root.hlsl
+build msl: phony gen/backdrop_lg.msl gen/backdrop.msl gen/bbox_clear.msl gen/binning.msl gen/coarse.msl gen/draw_leaf.msl gen/draw_reduce.msl gen/draw_root.msl gen/kernel4.msl gen/kernel4_gray.msl gen/path_coarse.msl gen/pathseg.msl gen/pathtag_reduce.msl gen/pathtag_root.msl gen/tile_alloc.msl gen/transform_leaf.msl gen/transform_reduce.msl gen/transform_root.msl
diff --git a/piet-gpu/shader/gen/backdrop.dxil b/piet-gpu/shader/gen/backdrop.dxil
index 10e1bd0..4ebcb1c 100644
Binary files a/piet-gpu/shader/gen/backdrop.dxil and b/piet-gpu/shader/gen/backdrop.dxil differ
diff --git a/piet-gpu/shader/gen/backdrop_lg.dxil b/piet-gpu/shader/gen/backdrop_lg.dxil
index 58e21a2..e6b2f1a 100644
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diff --git a/piet-gpu/shader/gen/bbox_clear.dxil b/piet-gpu/shader/gen/bbox_clear.dxil
index ec661f8..9ce0add 100644
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diff --git a/piet-gpu/shader/gen/binning.dxil b/piet-gpu/shader/gen/binning.dxil
index 849a59f..50034cc 100644
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diff --git a/piet-gpu/shader/gen/coarse.dxil b/piet-gpu/shader/gen/coarse.dxil
index a3e34c6..16d47ce 100644
Binary files a/piet-gpu/shader/gen/coarse.dxil and b/piet-gpu/shader/gen/coarse.dxil differ
diff --git a/piet-gpu/shader/gen/draw_leaf.dxil b/piet-gpu/shader/gen/draw_leaf.dxil
index b880f59..17bfd04 100644
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diff --git a/piet-gpu/shader/gen/draw_reduce.dxil b/piet-gpu/shader/gen/draw_reduce.dxil
index c6c9624..9b1b0fd 100644
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diff --git a/piet-gpu/shader/gen/draw_root.dxil b/piet-gpu/shader/gen/draw_root.dxil
index d0a326f..a84fd4a 100644
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diff --git a/piet-gpu/shader/gen/kernel4.dxil b/piet-gpu/shader/gen/kernel4.dxil
index 3e21354..3b3c42e 100644
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diff --git a/piet-gpu/shader/gen/kernel4_gray.dxil b/piet-gpu/shader/gen/kernel4_gray.dxil
index 7bd557b..6ec6d57 100644
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diff --git a/piet-gpu/shader/gen/path_coarse.dxil b/piet-gpu/shader/gen/path_coarse.dxil
index b6c9398..9fd593c 100644
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diff --git a/piet-gpu/shader/gen/pathseg.dxil b/piet-gpu/shader/gen/pathseg.dxil
index 657b340..3c81315 100644
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diff --git a/piet-gpu/shader/gen/pathtag_reduce.dxil b/piet-gpu/shader/gen/pathtag_reduce.dxil
index 78d2cf9..245c492 100644
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diff --git a/piet-gpu/shader/gen/pathtag_root.dxil b/piet-gpu/shader/gen/pathtag_root.dxil
index 48584bd..77f12e6 100644
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diff --git a/piet-gpu/shader/gen/tile_alloc.dxil b/piet-gpu/shader/gen/tile_alloc.dxil
index 1a97d82..d69db16 100644
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diff --git a/piet-gpu/shader/gen/transform_leaf.dxil b/piet-gpu/shader/gen/transform_leaf.dxil
index 915248b..32ec399 100644
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diff --git a/piet-gpu/shader/gen/transform_reduce.dxil b/piet-gpu/shader/gen/transform_reduce.dxil
index 5bd59c0..63df381 100644
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diff --git a/piet-gpu/shader/gen/transform_root.dxil b/piet-gpu/shader/gen/transform_root.dxil
index a33ff7f..5b4f059 100644
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