Overhaul wrapped lighting

Now:
* k=0   -> lambertian
* k=0.5 -> half lambertian
* k=1.0 -> flat

All three points should be energy conserving, but I haven't done the
actual analysis yet.

1 files changed, 17 insertions, 2 deletions

diff --git a/math.cginc b/math.cginc
index 8d404d9..bccb206 100644
--- a/math.cginc
+++ b/math.cginc
@@ -15,9 +15,24 @@ float pow5(float x)
   return (tmp * tmp) * x;

 }

 

-float wrapNoL(float NoL, float factor) {

+float wrapNoL(float NoL, float k) {

+#if 0

 		// https://www.iro.umontreal.ca/~derek/files/jgt_wrap_final.pdf

-    return pow(max(1E-4, (NoL + factor) / (1 + factor)), 1 + factor);

+    return pow(max(1E-4, (NoL + k) / (1 + k)), 1 + k);

+#else 

+    float k_sq = k * k;

+    float b = max(0, lerp(NoL, 1.0, k));

+    float p = -6.0 * k_sq + 5.0 * k + 1.0;

+    // Using the formula

+    float F = pow(b, p);

+

+    // Approximate integral of NoL with respect to theta

+    float I = 0.7856 * k_sq - 0.2148 * k + 1.0;

+

+    float G = F / max(I, 1E-6);

+

+    return G;

+#endif

 }

 

 float halfLambertianNoL(float NoL) {