1 files changed, 46 insertions, 0 deletions
diff --git a/source/blender/draw/engines/eevee/shaders/bsdf_lut_frag.glsl b/source/blender/draw/engines/eevee/shaders/bsdf_lut_frag.glsl
new file mode 100644
index 00000000000..7fb4ee51a96
--- /dev/null
+++ b/source/blender/draw/engines/eevee/shaders/bsdf_lut_frag.glsl
@@ -0,0 +1,46 @@
+
+out vec4 FragColor;
+
+void main() {
+	vec3 N, T, B, V;
+
+	float NV = ( 1.0 - (clamp(gl_FragCoord.y / BRDF_LUT_SIZE, 1e-4, 0.9999)));
+	float sqrtRoughness = clamp(gl_FragCoord.x / BRDF_LUT_SIZE, 1e-4, 0.9999);
+	float a = sqrtRoughness * sqrtRoughness;
+	float a2 = a * a;
+
+	N = vec3(0.0, 0.0, 1.0);
+	T = vec3(1.0, 0.0, 0.0);
+	B = vec3(0.0, 1.0, 0.0);
+	V = vec3(sqrt(1.0 - NV * NV), 0.0, NV);
+
+	setup_noise();
+
+	/* Integrating BRDF */
+	float brdf_accum = 0.0;
+	float fresnel_accum = 0.0;
+	for (float i = 0; i < sampleCount; i++) {
+		vec3 H = sample_ggx(i, a2, N, T, B); /* Microfacet normal */
+		vec3 L = -reflect(V, H);
+		float NL = L.z;
+
+		if (NL > 0.0) {
+			float NH = max(H.z, 0.0);
+			float VH = max(dot(V, H), 0.0);
+
+			float G1_v = G1_Smith_GGX(NV, a2);
+			float G1_l = G1_Smith_GGX(NL, a2);
+			float G_smith = 4.0 * NV * NL / (G1_v * G1_l); /* See G1_Smith_GGX for explanations. */
+
+			float brdf = (G_smith * VH) / (NH * NV);
+			float Fc = pow(1.0 - VH, 5.0);
+
+			brdf_accum += (1.0 - Fc) * brdf;
+			fresnel_accum += Fc * brdf;
+		}
+	}
+	brdf_accum /= sampleCount;
+	fresnel_accum /= sampleCount;
+
+	FragColor = vec4(brdf_accum, fresnel_accum, 0.0, 1.0);
+}