Cycles: Implement denoising option for reducing noise in the rendered image

This commit contains the first part of the new Cycles denoising option,
which filters the resulting image using information gathered during rendering
to get rid of noise while preserving visual features as well as possible.

To use the option, enable it in the render layer options. The default settings
fit a wide range of scenes, but the user can tweak individual settings to
control the tradeoff between a noise-free image, image details, and calculation
time.

Note that the denoiser may still change in the future and that some features
are not implemented yet. The most important missing feature is animation
denoising, which uses information from multiple frames at once to produce a
flicker-free and smoother result. These features will be added in the future.

Finally, thanks to all the people who supported this project:

- Google (through the GSoC) and Theory Studios for sponsoring the development
- The authors of the papers I used for implementing the denoiser (more details
  on them will be included in the technical docs)
- The other Cycles devs for feedback on the code, especially Sergey for
  mentoring the GSoC project and Brecht for the code review!
- And of course the users who helped with testing, reported bugs and things
  that could and/or should work better!

5 files changed, 19 insertions, 10 deletions

diff --git a/intern/cycles/kernel/svm/svm_closure.h b/intern/cycles/kernel/svm/svm_closure.h
index 407f8e784c0..7918c640175 100644
--- a/intern/cycles/kernel/svm/svm_closure.h
+++ b/intern/cycles/kernel/svm/svm_closure.h
@@ -444,6 +444,7 @@ ccl_device void svm_node_closure_bsdf(KernelGlobals *kg, ShaderData *sd, float *
 			ShaderClosure *bsdf = bsdf_alloc(sd, sizeof(ShaderClosure), weight);
 
 			if(bsdf) {
+				bsdf->N = N;
 				sd->flag |= bsdf_transparent_setup(bsdf);
 			}
 			break;
@@ -704,6 +705,7 @@ ccl_device void svm_node_closure_bsdf(KernelGlobals *kg, ShaderData *sd, float *
 				ShaderClosure *bsdf = bsdf_alloc(sd, sizeof(ShaderClosure), weight);
 
 				if(bsdf) {
+					bsdf->N = N;
 					/* todo: giving a fixed weight here will cause issues when
 					 * mixing multiple BSDFS. energy will not be conserved and
 					 * the throughput can blow up after multiple bounces. we
diff --git a/intern/cycles/kernel/svm/svm_displace.h b/intern/cycles/kernel/svm/svm_displace.h
index c94fa130af7..656357be52d 100644
--- a/intern/cycles/kernel/svm/svm_displace.h
+++ b/intern/cycles/kernel/svm/svm_displace.h
@@ -63,8 +63,13 @@ ccl_device void svm_node_set_bump(KernelGlobals *kg, ShaderData *sd, float *stac
 	strength = max(strength, 0.0f);
 
 	/* compute and output perturbed normal */
-	float3 normal_out = normalize(absdet*normal_in - distance*signf(det)*surfgrad);
-	normal_out = normalize(strength*normal_out + (1.0f - strength)*normal_in);
+	float3 normal_out = safe_normalize(absdet*normal_in - distance*signf(det)*surfgrad);
+	if(is_zero(normal_out)) {
+		normal_out = normal_in;
+	}
+	else {
+		normal_out = normalize(strength*normal_out + (1.0f - strength)*normal_in);
+	}
 
 	if(use_object_space) {
 		object_normal_transform(kg, sd, &normal_out);
diff --git a/intern/cycles/kernel/svm/svm_geometry.h b/intern/cycles/kernel/svm/svm_geometry.h
index 4a09d9f6653..cce4e89e715 100644
--- a/intern/cycles/kernel/svm/svm_geometry.h
+++ b/intern/cycles/kernel/svm/svm_geometry.h
@@ -37,6 +37,7 @@ ccl_device_inline void svm_node_geometry(KernelGlobals *kg,
 #ifdef __UV__
 		case NODE_GEOM_uv: data = make_float3(sd->u, sd->v, 0.0f); break;
 #endif
+		default: data = make_float3(0.0f, 0.0f, 0.0f);
 	}
 
 	stack_store_float3(stack, out_offset, data);
diff --git a/intern/cycles/kernel/svm/svm_image.h b/intern/cycles/kernel/svm/svm_image.h
index 328ff79223b..8e45dbfa5ff 100644
--- a/intern/cycles/kernel/svm/svm_image.h
+++ b/intern/cycles/kernel/svm/svm_image.h
@@ -317,8 +317,8 @@ ccl_device void svm_node_tex_environment(KernelGlobals *kg, ShaderData *sd, floa
 	float3 co = stack_load_float3(stack, co_offset);
 	float2 uv;
 
-	co = normalize(co);
-	
+	co = safe_normalize(co);
+
 	if(projection == 0)
 		uv = direction_to_equirectangular(co);
 	else
diff --git a/intern/cycles/kernel/svm/svm_types.h b/intern/cycles/kernel/svm/svm_types.h
index cc9b840b13f..d859cae1708 100644
--- a/intern/cycles/kernel/svm/svm_types.h
+++ b/intern/cycles/kernel/svm/svm_types.h
@@ -402,7 +402,6 @@ typedef enum ClosureType {
 	CLOSURE_BSDF_DIFFUSE_TOON_ID,
 
 	/* Glossy */
-	CLOSURE_BSDF_GLOSSY_ID,
 	CLOSURE_BSDF_REFLECTION_ID,
 	CLOSURE_BSDF_MICROFACET_GGX_ID,
 	CLOSURE_BSDF_MICROFACET_GGX_FRESNEL_ID,
@@ -423,14 +422,13 @@ typedef enum ClosureType {
 	CLOSURE_BSDF_HAIR_REFLECTION_ID,
 
 	/* Transmission */
-	CLOSURE_BSDF_TRANSMISSION_ID,
 	CLOSURE_BSDF_TRANSLUCENT_ID,
 	CLOSURE_BSDF_REFRACTION_ID,
 	CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID,
 	CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID,
+	CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_ID,
 	CLOSURE_BSDF_MICROFACET_BECKMANN_GLASS_ID,
 	CLOSURE_BSDF_MICROFACET_GGX_GLASS_ID,
-	CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_ID,
 	CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_FRESNEL_ID,
 	CLOSURE_BSDF_SHARP_GLASS_ID,
 	CLOSURE_BSDF_HAIR_TRANSMISSION_ID,
@@ -465,13 +463,16 @@ typedef enum ClosureType {
 /* watch this, being lazy with memory usage */
 #define CLOSURE_IS_BSDF(type) (type <= CLOSURE_BSDF_TRANSPARENT_ID)
 #define CLOSURE_IS_BSDF_DIFFUSE(type) (type >= CLOSURE_BSDF_DIFFUSE_ID && type <= CLOSURE_BSDF_DIFFUSE_TOON_ID)
-#define CLOSURE_IS_BSDF_GLOSSY(type) (type >= CLOSURE_BSDF_GLOSSY_ID && type <= CLOSURE_BSDF_HAIR_REFLECTION_ID)
-#define CLOSURE_IS_BSDF_TRANSMISSION(type) (type >= CLOSURE_BSDF_TRANSMISSION_ID && type <= CLOSURE_BSDF_HAIR_TRANSMISSION_ID)
+#define CLOSURE_IS_BSDF_GLOSSY(type) (type >= CLOSURE_BSDF_REFLECTION_ID && type <= CLOSURE_BSDF_HAIR_REFLECTION_ID)
+#define CLOSURE_IS_BSDF_TRANSMISSION(type) (type >= CLOSURE_BSDF_TRANSLUCENT_ID && type <= CLOSURE_BSDF_HAIR_TRANSMISSION_ID)
 #define CLOSURE_IS_BSDF_BSSRDF(type) (type == CLOSURE_BSDF_BSSRDF_ID || type == CLOSURE_BSDF_BSSRDF_PRINCIPLED_ID)
+#define CLOSURE_IS_BSDF_TRANSPARENT(type) (type == CLOSURE_BSDF_TRANSPARENT_ID)
 #define CLOSURE_IS_BSDF_ANISOTROPIC(type) (type >= CLOSURE_BSDF_MICROFACET_GGX_ANISO_ID && type <= CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ANISO_ID)
 #define CLOSURE_IS_BSDF_MULTISCATTER(type) (type == CLOSURE_BSDF_MICROFACET_MULTI_GGX_ID ||\
                                             type == CLOSURE_BSDF_MICROFACET_MULTI_GGX_ANISO_ID || \
                                             type == CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_ID)
+#define CLOSURE_IS_BSDF_MICROFACET(type) ((type >= CLOSURE_BSDF_REFLECTION_ID && type <= CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ANISO_ID) ||\
+                                          (type >= CLOSURE_BSDF_REFRACTION_ID && type <= CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_ID))
 #define CLOSURE_IS_BSDF_OR_BSSRDF(type) (type <= CLOSURE_BSSRDF_BURLEY_ID)
 #define CLOSURE_IS_BSSRDF(type) (type >= CLOSURE_BSSRDF_CUBIC_ID && type <= CLOSURE_BSSRDF_BURLEY_ID)
 #define CLOSURE_IS_VOLUME(type) (type >= CLOSURE_VOLUME_ID && type <= CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID)
@@ -480,7 +481,7 @@ typedef enum ClosureType {
 #define CLOSURE_IS_BACKGROUND(type) (type == CLOSURE_BACKGROUND_ID)
 #define CLOSURE_IS_AMBIENT_OCCLUSION(type) (type == CLOSURE_AMBIENT_OCCLUSION_ID)
 #define CLOSURE_IS_PHASE(type) (type == CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID)
-#define CLOSURE_IS_GLASS(type) (type >= CLOSURE_BSDF_MICROFACET_BECKMANN_GLASS_ID && type <= CLOSURE_BSDF_SHARP_GLASS_ID)
+#define CLOSURE_IS_GLASS(type) (type >= CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_ID && type <= CLOSURE_BSDF_SHARP_GLASS_ID)
 #define CLOSURE_IS_PRINCIPLED(type) (type == CLOSURE_BSDF_PRINCIPLED_ID)
 
 #define CLOSURE_WEIGHT_CUTOFF 1e-5f