Move phase to function

data/shaders/opengl/planetrings.frag

@@ -11,6 +11,15 @@ in vec4 varyingEyepos;
 
 out vec4 frag_color;
 
+float phaseFunction(const float g, const float mu)
+{
+	/*
+	* Use Mie phase function:
+	* https://www.scratchapixel.com/lessons/procedural-generation-virtual-worlds/simulating-sky/simulating-colors-of-the-sky.html
+	*/
+	return 3.f / (8.f * 3.141592) * ((1.f - g * g) * (1.f + mu * mu)) / ((2.f + g * g) * pow(1.f + g * g - 2.f * g * mu, 1.5f));
+}
+
 void main(void)
 {
 	// Bits of ring in shadow!
@@ -28,11 +37,11 @@ void main(void)
 
 			// second term: diffuse mie (scattering through ring)
 			float g = 0.76f;
-			float phaseThrough = 3.f / (8.f * 3.141592) * ((1.f - g * g) * (1.f + mu * mu)) / ((2.f + g * g) * pow(1.f + g * g - 2.f * g * mu, 1.5f));
+			float phaseThrough = phaseFunction(g, mu);
 
 			// third term: reflect mie (imitate albedo >= 1.0)
 			float muRev = dot(-normalize(vec3(uLight[i].position)), eyenorm);
-			float phaseReflect = 3.f / (8.f * 3.141592) * ((1.f - g * g) * (1.f + muRev * muRev)) / ((2.f + g * g) * pow(1.f + g * g - 2.f * g * muRev, 1.5f));
+			float phaseReflect = phaseFunction(g, muRev);
 
 			col = col + texCol * (diffuse + phaseThrough + phaseReflect) * uLight[i].diffuse;
 		}