From 155a8ceecfe64773eb21ba55a2ac286d52589141 Mon Sep 17 00:00:00 2001
From: yum <yum.food.vr@gmail.com>
Date: Tue, 24 Feb 2026 01:37:59 -0800
Subject: Rewrite SH9 core, more concise

---
 lighting.cginc | 35 ++++++++++++-----------------------
 1 file changed, 12 insertions(+), 23 deletions(-)

(limited to 'lighting.cginc')

diff --git a/lighting.cginc b/lighting.cginc
index 2ae7d0d..9a66703 100755
--- a/lighting.cginc
+++ b/lighting.cginc
@@ -139,36 +139,25 @@ float3 yumSH9(float4 n, float3 worldPos, inout LightIndirect light) {
   //   unity_SHB*:     first four of the L2 coefficients
   //   unity_SHC:      last L2 coefficient
 
-  // Parse out coefficients into a simpler but less efficient format.
-  float3 L00  = float3(unity_SHAr.w, unity_SHAg.w, unity_SHAb.w);
-  float3 L1_1 = float3(unity_SHAr.x, unity_SHAg.x, unity_SHAb.x);
-  float3 L10  = float3(unity_SHAr.y, unity_SHAg.y, unity_SHAb.y);
-  float3 L11  = float3(unity_SHAr.z, unity_SHAg.z, unity_SHAb.z);
-  float3 L2_2 = float3(unity_SHBr.x, unity_SHBg.x, unity_SHBb.x);
-  float3 L2_1 = float3(unity_SHBr.y, unity_SHBg.y, unity_SHBb.y);
-  float3 L20  = float3(unity_SHBr.z, unity_SHBg.z, unity_SHBb.z);
-  float3 L21  = float3(unity_SHBr.w, unity_SHBg.w, unity_SHBb.w);
-  float3 L22  = unity_SHC;
-
   // Equation 13 from "An Efficient Representation for Irradiance Environment
-  // Maps" by Ramamoorthi and Hanrahan. Note that the order of some
-  // coefficients is different, and normalization constants have been
-  // premultiplied by Unity.
-  float3 L0 = L00;
-  float3 L1 = L1_1 * n.x + L10 * n.y + L11 * n.z;
-  float3 L2 =
-    L2_2 * n.x * n.y +
-    L2_1 * n.y * n.z +
-    L20  * n.z * n.z +
-    L21 * n.x * n.z +
-    L22 * (n.x * n.x - n.y * n.y);
+  // Maps" by Ramamoorthi and Hanrahan. Normalization constants have been
+  // premultiplied by Unity into the coefficient buffers.
+  //
+  // L0+L1: dot4 per channel (n.w=1 picks up the L0 term from SHA*.w)
+  // L2: four quadratic terms packed into vB via swizzle multiply, plus L22
+  float4 n4 = float4(n.xyz, 1.0);
+  float3 L0 = float3(unity_SHAr.w, unity_SHAg.w, unity_SHAb.w);
+  float3 L01 = float3(dot(unity_SHAr, n4), dot(unity_SHAg, n4), dot(unity_SHAb, n4));
+  float4 vB = n4.xyzz * n4.yzzx;
+  float3 L2 = float3(dot(unity_SHBr, vB), dot(unity_SHBg, vB), dot(unity_SHBb, vB))
+            + unity_SHC * (n.x * n.x - n.y * n.y);
 
   light.L00 = L0;
   light.L01r = unity_SHAr.xyz;
   light.L01g = unity_SHAg.xyz;
   light.L01b = unity_SHAb.xyz;
 
-  return L0 + L1 + L2;
+  return L01 + L2;
 }
 
 float4 getIndirectDiffuse(v2f i, Pbr pbr, inout LightIndirect light) {
-- 
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