1 files changed, 33 insertions, 0 deletions
diff --git a/pbr/2.1.2.ibl_irradiance/convolution.frag b/pbr/2.1.2.ibl_irradiance/convolution.frag
new file mode 100644
index 0000000..69ce8af
--- /dev/null
+++ b/pbr/2.1.2.ibl_irradiance/convolution.frag
@@ -0,0 +1,33 @@
+#version 330 core
+
+in vert_t {
+	vec3 position;
+} vert;
+
+out vec4 frag_color;
+
+uniform samplerCube cubemap;
+
+const float PI = 3.14159265359;
+
+void main(void)
+{
+	vec3 normal = normalize(vert.position);
+	vec3 up = vec3(0.0, 1.0, 0.0);
+	vec3 right = cross(up, normal);
+	up = cross(normal, right);
+
+	vec3 irradiance = vec3(0.0);
+	float delta = 0.025;
+	int nsamples = 0;
+	for (float phi = 0.0; phi < 2.0 * PI; phi += delta) {
+		for (float theta = 0.0; theta < 0.5 * PI; theta += delta) {
+			vec3 tangent = vec3(sin(theta) * cos(phi), sin(theta) * sin(phi), cos(theta));
+			vec3 v = tangent.x * right + tangent.y * up + tangent.z * normal;
+			irradiance += texture(cubemap, v).rgb * cos(theta) * sin(theta);
+			nsamples++;
+		}
+	}
+	irradiance *= PI / nsamples;
+	frag_color = vec4(irradiance, 1.0);
+}