Implement IBL diffuse part

[opengl.git] / irradiancefrag.glsl

diff --git a/irradiancefrag.glsl b/irradiancefrag.glsl
new file mode 100644 (file)
index 0000000..a1cc027
--- /dev/null
+++ b/irradiancefrag.glsl
@@ -0,0 +1,34 @@
+#version 330
+
+in vec3 localPos;
+out vec4 fragColor;
+
+uniform samplerCube environmentMap;
+
+const float PI = 3.14159265359;
+
+void main() {
+       // sample dir = hemisphere's orientation
+       vec3 normal = normalize(localPos);
+       vec3 irradiance = vec3(0);
+
+       vec3 up = vec3(0, 1, 0);
+       vec3 right = cross(up, normal);
+       up = cross(normal, right);
+
+       const float sampleDelta = 0.025;
+       float numSamples = 0;
+       for (float phi = 0; phi < 2 * PI; phi += sampleDelta) {
+               for (float theta = 0; theta < 0.5 * PI; theta += sampleDelta) {
+                       vec3 tangentSample = vec3(sin(theta) * cos(phi), sin(theta) * sin(phi), cos(theta));
+                       // tangent space -> world space
+                       vec3 sampleVec = tangentSample.x * right + tangentSample.y * up + tangentSample.z * normal;
+                       irradiance += texture(environmentMap, sampleVec).rgb * cos(theta) * sin(theta);
+                       numSamples++;
+               }
+       }
+
+       irradiance = (PI * irradiance) / numSamples;
+
+       fragColor = vec4(irradiance, 1);
+}