[Bf-blender-cvs] [07dbff7dc1d] master: Fix T53217: GLSL principled BSDF black with zero clearcoat roughness.

[Brecht Van Lommel]

Commit: 07dbff7dc1d5cfca9fbfb74204a2298e16d471b4
Author: Brecht Van Lommel
Date:   Wed Nov 1 17:12:36 2017 +0100
Branches: master
https://developer.blender.org/rB07dbff7dc1d5cfca9fbfb74204a2298e16d471b4

Fix T53217: GLSL principled BSDF black with zero clearcoat roughness.

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M	source/blender/gpu/shaders/gpu_shader_material.glsl

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diff --git a/source/blender/gpu/shaders/gpu_shader_material.glsl b/source/blender/gpu/shaders/gpu_shader_material.glsl
index 3dbecc58a7e..ce696706628 100644
--- a/source/blender/gpu/shaders/gpu_shader_material.glsl
+++ b/source/blender/gpu/shaders/gpu_shader_material.glsl
@@ -2524,7 +2524,11 @@ float schlick_fresnel(float u)
 
 float GTR1(float NdotH, float a)
 {
-	if (a >= 1.0) return M_1_PI;
+	if (a >= 1.0) {
+		return M_1_PI;
+	}
+
+	a = max(a, 0.001);
 	float a2 = a*a;
 	float t = 1.0 + (a2 - 1.0) * NdotH*NdotH;
 	return (a2 - 1.0) / (M_PI * log(a2) * t);