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!

1 files changed, 68 insertions, 21 deletions

diff --git a/intern/cycles/kernel/kernel_types.h b/intern/cycles/kernel/kernel_types.h
index 9b354457b91..dd1fa1b82f7 100644
--- a/intern/cycles/kernel/kernel_types.h
+++ b/intern/cycles/kernel/kernel_types.h
@@ -173,6 +173,8 @@ CCL_NAMESPACE_BEGIN
 #define __PATCH_EVAL__
 #define __SHADOW_TRICKS__
 
+#define __DENOISING_FEATURES__
+
 #ifdef __KERNEL_SHADING__
 #  define __SVM__
 #  define __EMISSION__
@@ -314,31 +316,32 @@ enum SamplingPattern {
 /* these flags values correspond to raytypes in osl.cpp, so keep them in sync! */
 
 enum PathRayFlag {
-	PATH_RAY_CAMERA = 1,
-	PATH_RAY_REFLECT = 2,
-	PATH_RAY_TRANSMIT = 4,
-	PATH_RAY_DIFFUSE = 8,
-	PATH_RAY_GLOSSY = 16,
-	PATH_RAY_SINGULAR = 32,
-	PATH_RAY_TRANSPARENT = 64,
-
-	PATH_RAY_SHADOW_OPAQUE = 128,
-	PATH_RAY_SHADOW_TRANSPARENT = 256,
+	PATH_RAY_CAMERA              = (1 << 0),
+	PATH_RAY_REFLECT             = (1 << 1),
+	PATH_RAY_TRANSMIT            = (1 << 2),
+	PATH_RAY_DIFFUSE             = (1 << 3),
+	PATH_RAY_GLOSSY              = (1 << 4),
+	PATH_RAY_SINGULAR            = (1 << 5),
+	PATH_RAY_TRANSPARENT         = (1 << 6),
+
+	PATH_RAY_SHADOW_OPAQUE       = (1 << 7),
+	PATH_RAY_SHADOW_TRANSPARENT  = (1 << 8),
 	PATH_RAY_SHADOW = (PATH_RAY_SHADOW_OPAQUE|PATH_RAY_SHADOW_TRANSPARENT),
 
-	PATH_RAY_CURVE = 512, /* visibility flag to define curve segments */
-	PATH_RAY_VOLUME_SCATTER = 1024, /* volume scattering */
+	PATH_RAY_CURVE               = (1 << 9), /* visibility flag to define curve segments */
+	PATH_RAY_VOLUME_SCATTER      = (1 << 10), /* volume scattering */
 
 	/* Special flag to tag unaligned BVH nodes. */
-	PATH_RAY_NODE_UNALIGNED = 2048,
+	PATH_RAY_NODE_UNALIGNED = (1 << 11),
 
-	PATH_RAY_ALL_VISIBILITY = (1|2|4|8|16|32|64|128|256|512|1024|2048),
+	PATH_RAY_ALL_VISIBILITY = ((1 << 12)-1),
 
-	PATH_RAY_MIS_SKIP = 4096,
-	PATH_RAY_DIFFUSE_ANCESTOR = 8192,
-	PATH_RAY_SINGLE_PASS_DONE = 16384,
-	PATH_RAY_SHADOW_CATCHER = 32768,
-	PATH_RAY_SHADOW_CATCHER_ONLY = 65536,
+	PATH_RAY_MIS_SKIP            = (1 << 12),
+	PATH_RAY_DIFFUSE_ANCESTOR    = (1 << 13),
+	PATH_RAY_SINGLE_PASS_DONE    = (1 << 14),
+	PATH_RAY_SHADOW_CATCHER      = (1 << 15),
+	PATH_RAY_SHADOW_CATCHER_ONLY = (1 << 16),
+	PATH_RAY_STORE_SHADOW_INFO   = (1 << 17),
 };
 
 /* Closure Label */
@@ -394,6 +397,22 @@ typedef enum PassType {
 
 #define PASS_ALL (~0)
 
+typedef enum DenoisingPassOffsets {
+	DENOISING_PASS_NORMAL             = 0,
+	DENOISING_PASS_NORMAL_VAR         = 3,
+	DENOISING_PASS_ALBEDO             = 6,
+	DENOISING_PASS_ALBEDO_VAR         = 9,
+	DENOISING_PASS_DEPTH              = 12,
+	DENOISING_PASS_DEPTH_VAR          = 13,
+	DENOISING_PASS_SHADOW_A           = 14,
+	DENOISING_PASS_SHADOW_B           = 17,
+	DENOISING_PASS_COLOR              = 20,
+	DENOISING_PASS_COLOR_VAR          = 23,
+
+	DENOISING_PASS_SIZE_BASE          = 26,
+	DENOISING_PASS_SIZE_CLEAN         = 3,
+} DenoisingPassOffsets;
+
 typedef enum BakePassFilter {
 	BAKE_FILTER_NONE = 0,
 	BAKE_FILTER_DIRECT = (1 << 0),
@@ -427,6 +446,18 @@ typedef enum BakePassFilterCombos {
 	BAKE_FILTER_SUBSURFACE_INDIRECT = (BAKE_FILTER_INDIRECT | BAKE_FILTER_SUBSURFACE),
 } BakePassFilterCombos;
 
+typedef enum DenoiseFlag {
+	DENOISING_CLEAN_DIFFUSE_DIR      = (1 << 0),
+	DENOISING_CLEAN_DIFFUSE_IND      = (1 << 1),
+	DENOISING_CLEAN_GLOSSY_DIR       = (1 << 2),
+	DENOISING_CLEAN_GLOSSY_IND       = (1 << 3),
+	DENOISING_CLEAN_TRANSMISSION_DIR = (1 << 4),
+	DENOISING_CLEAN_TRANSMISSION_IND = (1 << 5),
+	DENOISING_CLEAN_SUBSURFACE_DIR   = (1 << 6),
+	DENOISING_CLEAN_SUBSURFACE_IND   = (1 << 7),
+	DENOISING_CLEAN_ALL_PASSES       = (1 << 8)-1,
+} DenoiseFlag;
+
 typedef ccl_addr_space struct PathRadiance {
 #ifdef __PASSES__
 	int use_light_pass;
@@ -482,6 +513,12 @@ typedef ccl_addr_space struct PathRadiance {
 	/* Color of the background on which shadow is alpha-overed. */
 	float3 shadow_color;
 #endif
+
+#ifdef __DENOISING_FEATURES__
+	float3 denoising_normal;
+	float3 denoising_albedo;
+	float denoising_depth;
+#endif  /* __DENOISING_FEATURES__ */
 } PathRadiance;
 
 typedef struct BsdfEval {
@@ -724,12 +761,13 @@ typedef struct AttributeDescriptor {
 #define SHADER_CLOSURE_BASE \
 	float3 weight; \
 	ClosureType type; \
-	float sample_weight \
+	float sample_weight; \
+	float3 N
 
 typedef ccl_addr_space struct ccl_align(16) ShaderClosure {
 	SHADER_CLOSURE_BASE;
 
-	float data[14]; /* pad to 80 bytes */
+	float data[10]; /* pad to 80 bytes */
 } ShaderClosure;
 
 /* Shader Context
@@ -960,6 +998,10 @@ typedef struct PathState {
 	int transmission_bounce;
 	int transparent_bounce;
 
+#ifdef __DENOISING_FEATURES__
+	float denoising_feature_weight;
+#endif  /* __DENOISING_FEATURES__ */
+
 	/* multiple importance sampling */
 	float min_ray_pdf; /* smallest bounce pdf over entire path up to now */
 	float ray_pdf;     /* last bounce pdf */
@@ -1137,6 +1179,11 @@ typedef struct KernelFilm {
 	float mist_inv_depth;
 	float mist_falloff;
 
+	int pass_denoising_data;
+	int pass_denoising_clean;
+	int denoising_flags;
+	int pad;
+
 #ifdef __KERNEL_DEBUG__
 	int pass_bvh_traversed_nodes;
 	int pass_bvh_traversed_instances;