1 files changed, 18 insertions, 33 deletions
diff --git a/lighting.cginc b/lighting.cginc
index 48d95a1..6668459 100644
--- a/lighting.cginc
+++ b/lighting.cginc
@@ -114,50 +114,35 @@ 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;
+  // L0 band
+  float3 L0 = float3(unity_SHAr.w, unity_SHAg.w, unity_SHAb.w);
+
+  // L1 band
+  float3 L1 = float3(
+    dot(unity_SHAr.xyz, n.xyz),
+    dot(unity_SHAg.xyz, n.xyz),
+    dot(unity_SHAb.xyz, n.xyz)
+  );
+
+  // L2 band
+  float4 v = float4(n.x * n.y, n.y * n.z, n.z * n.z, n.x * 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);
+    float3(dot(unity_SHBr.xyzw, v), dot(unity_SHBg.xyzw, v), dot(unity_SHBb.xyzw, v)) +
+    unity_SHC.xyz * (n.x * n.x - n.y * n.y);
 
   // TODO expose this as a parameter
   float wrap_term = 0.0f;
+
   // Original coefficients: 1, 2/3, 1/4.
   // Wrapped coefficients: 1, (2-w)/3, ((1-w)^2)/4.
-
-  // Setting w=0, the l1 band is:
-  //   (2-w)/3 = 2/3
-  //   2-w = 2
-  //   1-w/2 = 1
   float l1_wrap = 1.0f - wrap_term * 0.75f;
   L1 *= l1_wrap;
 
-  // The l2 band is:
-  //   ((1-w)^2)/4 = 1/4
-  //   (1-w)^2 = 1
-  float l2_wrap = (1.0f-wrap_term);
-  l2_wrap *= l2_wrap;
+  float l2_wrap_base = 1.0f - wrap_term;
+  float l2_wrap = l2_wrap_base * l2_wrap_base;
   L2 *= l2_wrap;
 
-  light.L00 = L00;
+  light.L00 = L0;
   light.L01r = unity_SHAr.xyz * l1_wrap;
   light.L01g = unity_SHAg.xyz * l1_wrap;
   light.L01b = unity_SHAb.xyz * l1_wrap;