SuperTuxKart 1.5 upstream source (from official release tarball)

data/shaders/utils/SunMRP.frag

@@ -0,0 +1,14 @@
+// Sun Most Representative Point (used for MRP area lighting method)
+// From "Frostbite going PBR" paper
+vec3 SunMRP(vec3 normal, vec3 eyedir)
+{
+    vec3 local_sundir = normalize((transpose(u_inverse_view_matrix) * vec4(sundirection, 0.)).xyz);
+    vec3 R = reflect(-eyedir, normal);
+    float angularRadius = 3.14 * sun_angle / 180.;
+    vec3 D = local_sundir;
+    float d = cos(angularRadius);
+    float r = sin(angularRadius);
+    float DdotR = dot(D, R);
+    vec3 S = R - DdotR * D;
+    return (DdotR < d) ? normalize(d * D + normalize (S) * r) : R;
+}