Simplify spherical harmonics

Implement standard SH9 as a learning exercise. Drop poi's fancy SH9
code. Realize that we just want diffuse and lock everything else away
behind a ui-inaccessible #define.

1 files changed, 43 insertions, 7 deletions

diff --git a/yum_lighting.cginc b/yum_lighting.cginc
index b8856ed..23e360e 100644
--- a/yum_lighting.cginc
+++ b/yum_lighting.cginc
@@ -142,13 +142,54 @@ float3 getIndirectSpecular(v2f i, YumPbr pbr, float3 view_dir) {
   return UnityGI_prefilteredRadiance(data, roughness, reflect_dir);

 }

 

+float3 yumSH9(float4 n) {

+#if defined(YUM_SH9_STANDARD)

+  // Unity gives us the first three bands (L0-L2) of SH coefficients as follows:

+  //   unity_SHA*.w:   L0 coefficients

+  //   unity_SHA*.xyz: L1 coefficients

+  //   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);

+

+  return L0 + L1 + L2;

+#else

+  // On non-photorealistic avatars, simply using the diffuse component looks

+  // better. *shruge*

+  float3 L00  = float3(unity_SHAr.w, unity_SHAg.w, unity_SHAb.w);

+  return L00;

+#endif

+}

+

 float4 getIndirectDiffuse(v2f i, float4 vertexLightColor) {

 	float4 diffuse = vertexLightColor;

 #if defined(FORWARD_BASE_PASS)

 #if defined(LIGHTMAP_ON)

 	diffuse.xyz = DecodeLightmap(UNITY_SAMPLE_TEX2D(unity_Lightmap, i.uv2));

 #else

-	diffuse.xyz += max(0, BetterSH9(float4(0, 0, 0, 1)));

+	diffuse.xyz += max(0, yumSH9(float4(0, 0, 0, 1)));

 #endif

 #endif

 	return diffuse;

@@ -169,12 +210,7 @@ YumLighting GetYumLighting(v2f i, YumPbr pbr) {
 	light.direct = _LightColor0.rgb;

 	// TODO filament's spherical harmonics look nicer than this.

 	// See FilamentLightIndirect.cginc::UnityGI_Irradiance in filamented.

-  //ifex _Spherical_Harmonics==0

-	light.diffuse = max(0, BetterSH9(float4(i.normal, 1)));

-  //endex

-  //ifex _Spherical_Harmonics==1

-	light.diffuse = max(0, BetterSH9(float4(0, 0, 0, 1)));

-  //endex

+  light.diffuse = getIndirectDiffuse(i, /*vertexLightColor=*/0);

 #if defined(_MIN_BRIGHTNESS)

   light.diffuse = max(_Min_Brightness, light.diffuse);

 #endif