Cycles: Experiment with replacing Sharp Glossy with GGX when Filter Glossy is used

The idea is to make it simpler to remove noise from scenes when some prop uses
Sharp glossy closure and causes noise in certain cases. Previously Sharp Glossy
was not affected by Filter Glossy at all, which was quite confusing.

Here is a file which demonstrates the issue: {F417797}

After applying the patch all the noise from the scene is gone.

This change also solves fireflies reported in T50700.

Reviewers: brecht, lukasstockner97

Differential Revision: https://developer.blender.org/D2416

1 files changed, 60 insertions, 12 deletions

diff --git a/intern/cycles/render/nodes.cpp b/intern/cycles/render/nodes.cpp
index 13b149eddfa..3ac3be20bd0 100644
--- a/intern/cycles/render/nodes.cpp
+++ b/intern/cycles/render/nodes.cpp
@@ -1931,21 +1931,36 @@ GlossyBsdfNode::GlossyBsdfNode()
 void GlossyBsdfNode::simplify_settings(Scene *scene)
 {
 	if(distribution_orig == NBUILTIN_CLOSURES) {
+		roughness_orig = roughness;
 		distribution_orig = distribution;
 	}
+	else {
+		/* By default we use original values, so we don't worry about restoring
+		 * defaults later one and can only do override when needed.
+		 */
+		roughness = roughness_orig;
+		distribution = distribution_orig;
+	}
 	Integrator *integrator = scene->integrator;
+	ShaderInput *roughness_input = input("Roughness");
 	if(integrator->filter_glossy == 0.0f) {
 		/* Fallback to Sharp closure for Roughness close to 0.
 		 * Note: Keep the epsilon in sync with kernel!
 		 */
-		ShaderInput *roughness_input = input("Roughness");
 		if(!roughness_input->link && roughness <= 1e-4f) {
 			distribution = CLOSURE_BSDF_REFLECTION_ID;
 		}
 	}
 	else {
-		/* Rollback to original distribution when filter glossy is used. */
-		distribution = distribution_orig;
+		/* If filter glossy is used we replace Sharp glossy with GGX so we can
+		 * benefit from closure blur to remove unwanted noise.
+		 */
+		if(roughness_input->link == NULL &&
+		   distribution == CLOSURE_BSDF_REFLECTION_ID)
+		{
+			distribution = CLOSURE_BSDF_MICROFACET_GGX_ID;
+			roughness = 0.0f;
+		}
 	}
 	closure = distribution;
 }
@@ -1953,7 +1968,8 @@ void GlossyBsdfNode::simplify_settings(Scene *scene)
 bool GlossyBsdfNode::has_integrator_dependency()
 {
 	ShaderInput *roughness_input = input("Roughness");
-	return !roughness_input->link && roughness <= 1e-4f;
+	return !roughness_input->link &&
+	       (distribution == CLOSURE_BSDF_REFLECTION_ID || roughness <= 1e-4f);
 }
 
 void GlossyBsdfNode::compile(SVMCompiler& compiler)
@@ -2008,21 +2024,36 @@ GlassBsdfNode::GlassBsdfNode()
 void GlassBsdfNode::simplify_settings(Scene *scene)
 {
 	if(distribution_orig == NBUILTIN_CLOSURES) {
+		roughness_orig = roughness;
 		distribution_orig = distribution;
 	}
+	else {
+		/* By default we use original values, so we don't worry about restoring
+		 * defaults later one and can only do override when needed.
+		 */
+		roughness = roughness_orig;
+		distribution = distribution_orig;
+	}
 	Integrator *integrator = scene->integrator;
+	ShaderInput *roughness_input = input("Roughness");
 	if(integrator->filter_glossy == 0.0f) {
 		/* Fallback to Sharp closure for Roughness close to 0.
 		 * Note: Keep the epsilon in sync with kernel!
 		 */
-		ShaderInput *roughness_input = input("Roughness");
 		if(!roughness_input->link && roughness <= 1e-4f) {
 			distribution = CLOSURE_BSDF_SHARP_GLASS_ID;
 		}
 	}
 	else {
-		/* Rollback to original distribution when filter glossy is used. */
-		distribution = distribution_orig;
+		/* If filter glossy is used we replace Sharp glossy with GGX so we can
+		 * benefit from closure blur to remove unwanted noise.
+		 */
+		if(roughness_input->link == NULL &&
+		   distribution == CLOSURE_BSDF_SHARP_GLASS_ID)
+		{
+			distribution = CLOSURE_BSDF_MICROFACET_GGX_GLASS_ID;
+			roughness = 0.0f;
+		}
 	}
 	closure = distribution;
 }
@@ -2030,7 +2061,8 @@ void GlassBsdfNode::simplify_settings(Scene *scene)
 bool GlassBsdfNode::has_integrator_dependency()
 {
 	ShaderInput *roughness_input = input("Roughness");
-	return !roughness_input->link && roughness <= 1e-4f;
+	return !roughness_input->link &&
+	       (distribution == CLOSURE_BSDF_SHARP_GLASS_ID || roughness <= 1e-4f);
 }
 
 void GlassBsdfNode::compile(SVMCompiler& compiler)
@@ -2085,21 +2117,36 @@ RefractionBsdfNode::RefractionBsdfNode()
 void RefractionBsdfNode::simplify_settings(Scene *scene)
 {
 	if(distribution_orig == NBUILTIN_CLOSURES) {
+		roughness_orig = roughness;
 		distribution_orig = distribution;
 	}
+	else {
+		/* By default we use original values, so we don't worry about restoring
+		 * defaults later one and can only do override when needed.
+		 */
+		roughness = roughness_orig;
+		distribution = distribution_orig;
+	}
 	Integrator *integrator = scene->integrator;
+	ShaderInput *roughness_input = input("Roughness");
 	if(integrator->filter_glossy == 0.0f) {
 		/* Fallback to Sharp closure for Roughness close to 0.
 		 * Note: Keep the epsilon in sync with kernel!
 		 */
-		ShaderInput *roughness_input = input("Roughness");
 		if(!roughness_input->link && roughness <= 1e-4f) {
 			distribution = CLOSURE_BSDF_REFRACTION_ID;
 		}
 	}
 	else {
-		/* Rollback to original distribution when filter glossy is used. */
-		distribution = distribution_orig;
+		/* If filter glossy is used we replace Sharp glossy with GGX so we can
+		 * benefit from closure blur to remove unwanted noise.
+		 */
+		if(roughness_input->link == NULL &&
+		   distribution == CLOSURE_BSDF_REFRACTION_ID)
+		{
+			distribution = CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID;
+			roughness = 0.0f;
+		}
 	}
 	closure = distribution;
 }
@@ -2107,7 +2154,8 @@ void RefractionBsdfNode::simplify_settings(Scene *scene)
 bool RefractionBsdfNode::has_integrator_dependency()
 {
 	ShaderInput *roughness_input = input("Roughness");
-	return !roughness_input->link && roughness <= 1e-4f;
+	return !roughness_input->link &&
+	       (distribution == CLOSURE_BSDF_REFRACTION_ID || roughness <= 1e-4f);
 }
 
 void RefractionBsdfNode::compile(SVMCompiler& compiler)