refactor(shaders): extract oct-normal encode/decode into math/normal snippet

New src/shaders/math/normal.wgsl: oct_encode, oct_decode, oct_encode_unorm,
oct_decode_unorm. Registered in InitShaderComposer as "math/normal".
Removed inline copies from gbuf_raster.wgsl and gbuf_pack.wgsl.
18/18 tests passing.

1 files changed, 2 insertions, 15 deletions

diff --git a/cnn_v3/shaders/gbuf_raster.wgsl b/cnn_v3/shaders/gbuf_raster.wgsl
index c762db2..a5eb921 100644
--- a/cnn_v3/shaders/gbuf_raster.wgsl
+++ b/cnn_v3/shaders/gbuf_raster.wgsl
@@ -3,6 +3,7 @@
 // Uses GlobalUniforms, ObjectData, ObjectsBuffer from common_uniforms.
 
 #include "common_uniforms"
+#include "math/normal"
 
 @group(0) @binding(0) var<uniform> globals: GlobalUniforms;
 @group(0) @binding(1) var<storage, read> object_data: ObjectsBuffer;
@@ -15,20 +16,6 @@ struct VertexOutput {
     @location(3) @interpolate(flat) instance_index: u32,
 }
 
-// Octahedral encoding: maps unit normal to [-1,1]^2
-fn oct_encode(n: vec3f) -> vec2f {
-    let inv_l1 = 1.0 / (abs(n.x) + abs(n.y) + abs(n.z));
-    var p = n.xy * inv_l1;
-    // Fold lower hemisphere
-    if (n.z < 0.0) {
-        let s = vec2f(
-            select(-1.0, 1.0, p.x >= 0.0),
-            select(-1.0, 1.0, p.y >= 0.0)
-        );
-        p = (1.0 - abs(p.yx)) * s;
-    }
-    return p; // in [-1, 1]
-}
 
 @vertex
 fn vs_main(
@@ -96,7 +83,7 @@ fn fs_main(in: VertexOutput) -> GBufOutput {
     let mat_id = f32(in.instance_index) / 255.0;
 
     // Oct-encode world normal, remap [-1,1] → [0,1] for storage
-    let oct = oct_encode(normalize(in.world_normal)) * 0.5 + vec2f(0.5);
+    let oct = oct_encode_unorm(normalize(in.world_normal));
 
     var out: GBufOutput;
     out.albedo     = vec4f(in.color.rgb, 1.0);