Fix #34740: cycles rendering issue mixing glossy/glass BSDF's with zero or very

low roughness and same index of refraction.

Problem was bad float precision due to low roughness, which caused the pdf for
the different closures to not match properly.

2 files changed, 10 insertions, 10 deletions

diff --git a/intern/cycles/kernel/closure/bsdf_microfacet.h b/intern/cycles/kernel/closure/bsdf_microfacet.h
index 019ec105111..b771e02f131 100644
--- a/intern/cycles/kernel/closure/bsdf_microfacet.h
+++ b/intern/cycles/kernel/closure/bsdf_microfacet.h
@@ -46,7 +46,7 @@ __device int bsdf_microfacet_ggx_setup(ShaderClosure *sc)
 {
 	float ag = sc->data0;
 
-	float m_ag = clamp(ag, 1e-4f, 1.0f);
+	float m_ag = clamp(ag, 1e-3f, 1.0f);
 
 	sc->data0 = m_ag;
 	sc->type = CLOSURE_BSDF_MICROFACET_GGX_ID;
@@ -59,7 +59,7 @@ __device int bsdf_microfacet_ggx_refraction_setup(ShaderClosure *sc)
 	float ag = sc->data0;
 	float eta = sc->data1;
 
-	float m_ag = clamp(ag, 1e-4f, 1.0f);
+	float m_ag = clamp(ag, 1e-3f, 1.0f);
 	float m_eta = eta;
 
 	sc->data0 = m_ag;
@@ -256,7 +256,7 @@ __device int bsdf_microfacet_ggx_sample(const ShaderClosure *sc, float3 Ng, floa
 __device int bsdf_microfacet_beckmann_setup(ShaderClosure *sc)
 {
 	float ab = sc->data0;
-	float m_ab = clamp(ab, 1e-4f, 1.0f);
+	float m_ab = clamp(ab, 1e-3f, 1.0f);
 
 	sc->data0 = m_ab;
 
@@ -268,7 +268,7 @@ __device int bsdf_microfacet_beckmann_refraction_setup(ShaderClosure *sc)
 {
 	float ab = sc->data0;
 	float eta = sc->data1;
-	float m_ab = clamp(ab, 1e-4f, 1.0f);
+	float m_ab = clamp(ab, 1e-3f, 1.0f);
 	float m_eta = eta;
 
 	sc->data0 = m_ab;
@@ -343,7 +343,7 @@ __device float3 bsdf_microfacet_beckmann_eval_transmit(const ShaderClosure *sc,
 	float cosHI = dot(Ht, omega_in);
 	// eq. 33: first we calculate D(m) with m=Ht:
 	float alpha2 = m_ab * m_ab;
-	float cosThetaM = dot(N, Ht);
+	float cosThetaM = min(dot(N, Ht), 1.0f);
 	float cosThetaM2 = cosThetaM * cosThetaM;
 	float tanThetaM2 = (1 - cosThetaM2) / cosThetaM2;
 	float cosThetaM4 = cosThetaM2 * cosThetaM2;
@@ -405,8 +405,8 @@ __device int bsdf_microfacet_beckmann_sample(const ShaderClosure *sc, float3 Ng,
 					// Eval BRDF*cosNI
 					float cosNI = dot(N, *omega_in);
 					// eq. 26, 27: now calculate G1(i,m) and G1(o,m)
-					float ao = 1 / (m_ab * safe_sqrtf((1 - cosNO * cosNO) / (cosNO * cosNO)));
-					float ai = 1 / (m_ab * safe_sqrtf((1 - cosNI * cosNI) / (cosNI * cosNI)));
+					float ao = 1 / (safe_sqrtf(alpha2 * (1 - cosNO * cosNO) / (cosNO * cosNO)));
+					float ai = 1 / (safe_sqrtf(alpha2 * (1 - cosNI * cosNI) / (cosNI * cosNI)));
 					float G1o = ao < 1.6f ? (3.535f * ao + 2.181f * ao * ao) / (1 + 2.276f * ao + 2.577f * ao * ao) : 1.0f;
 					float G1i = ai < 1.6f ? (3.535f * ai + 2.181f * ai * ai) / (1 + 2.276f * ai + 2.577f * ai * ai) : 1.0f;
 					float G = G1o * G1i;
@@ -452,8 +452,8 @@ __device int bsdf_microfacet_beckmann_sample(const ShaderClosure *sc, float3 Ng,
 				// eval BRDF*cosNI
 				float cosNI = dot(N, *omega_in);
 				// eq. 26, 27: now calculate G1(i,m) and G1(o,m)
-				float ao = 1 / (m_ab * safe_sqrtf((1 - cosNO * cosNO) / (cosNO * cosNO)));
-				float ai = 1 / (m_ab * safe_sqrtf((1 - cosNI * cosNI) / (cosNI * cosNI)));
+				float ao = 1 / (safe_sqrtf(alpha2 * (1 - cosNO * cosNO) / (cosNO * cosNO)));
+				float ai = 1 / (safe_sqrtf(alpha2 * (1 - cosNI * cosNI) / (cosNI * cosNI)));
 				float G1o = ao < 1.6f ? (3.535f * ao + 2.181f * ao * ao) / (1 + 2.276f * ao + 2.577f * ao * ao) : 1.0f;
 				float G1i = ai < 1.6f ? (3.535f * ai + 2.181f * ai * ai) / (1 + 2.276f * ai + 2.577f * ai * ai) : 1.0f;
 				float G = G1o * G1i;
diff --git a/intern/cycles/kernel/closure/bsdf_refraction.h b/intern/cycles/kernel/closure/bsdf_refraction.h
index ef79d6cc259..8565c99d04e 100644
--- a/intern/cycles/kernel/closure/bsdf_refraction.h
+++ b/intern/cycles/kernel/closure/bsdf_refraction.h
@@ -74,7 +74,7 @@ __device int bsdf_refraction_sample(const ShaderClosure *sc, float3 Ng, float3 I
 		&inside);
 	
 	if(!inside) {
-		*pdf = 1;
+		*pdf = 1.0f;
 		*eval = make_float3(1.0f, 1.0f, 1.0f);
 		*omega_in = T;
 #ifdef __RAY_DIFFERENTIALS__