Schlick BSDF: Add clamping to avoid some small floating point errors

Author: CodeFHD

include/slg/materials/materialdefs_funcs_generic.cl

@@ -228,7 +228,8 @@ OPENCL_FORCE_INLINE float3 SchlickBSDF_CoatingF(const float3 ks, const float rou
 	const float cosi = fabs(sampledDir.z);
 
 	const float3 wh = normalize(fixedDir + sampledDir);
-	const float3 S = FresnelSchlick_Evaluate(ks, fabs(dot(sampledDir, wh)));
+	const float cosi_Schlick = clamp(fabs(dot(sampledDir, wh)), 0.f, 1.f);
+	const float3 S = FresnelSchlick_Evaluate(ks, cosi_Schlick);
 
 	const float G = SchlickDistribution_G(roughness, fixedDir, sampledDir);
 

src/slg/materials/material.cpp

@@ -503,7 +503,8 @@ Spectrum slg::SchlickBSDF_CoatingF(const bool fromLight, const Spectrum &ks, con
 	const float cosi = fabsf(localSampledDir.z);
 
 	const Vector wh(Normalize(localFixedDir + localSampledDir));
-	const Spectrum S = FresnelTexture::SchlickEvaluate(ks, AbsDot(localSampledDir, wh));
+	const float cosi_Schlick = Clamp(AbsDot(localSampledDir, wh), 0.f, 1.f);
+	const Spectrum S = FresnelTexture::SchlickEvaluate(ks, cosi_Schlick);
 	assert (S.IsValid());
 
 	const float G = SchlickDistribution_G(roughness, localFixedDir, localSampledDir);