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, 12 insertions, 3 deletions

diff --git a/intern/cycles/render/buffers.h b/intern/cycles/render/buffers.h
index 5c78971678a..e56556c8abe 100644
--- a/intern/cycles/render/buffers.h
+++ b/intern/cycles/render/buffers.h
@@ -51,6 +51,9 @@ public:
 
 	/* passes */
 	array<Pass> passes;
+	bool denoising_data_pass;
+	/* If only some light path types should be denoised, an additional pass is needed. */
+	bool denoising_clean_pass;
 
 	/* functions */
 	BufferParams();
@@ -59,6 +62,7 @@ public:
 	bool modified(const BufferParams& params);
 	void add_pass(PassType type);
 	int get_passes_size();
+	int get_denoising_offset();
 };
 
 /* Render Buffers */
@@ -73,18 +77,19 @@ public:
 	/* random number generator state */
 	device_vector<uint> rng_state;
 
+	Device *device;
+
 	explicit RenderBuffers(Device *device);
 	~RenderBuffers();
 
 	void reset(Device *device, BufferParams& params);
 
-	bool copy_from_device();
+	bool copy_from_device(Device *from_device = NULL);
 	bool get_pass_rect(PassType type, float exposure, int sample, int components, float *pixels);
+	bool get_denoising_pass_rect(int offset, float exposure, int sample, int components, float *pixels);
 
 protected:
 	void device_free();
-
-	Device *device;
 };
 
 /* Display Buffer
@@ -131,6 +136,9 @@ protected:
 
 class RenderTile {
 public:
+	typedef enum { PATH_TRACE, DENOISE } Task;
+
+	Task task;
 	int x, y, w, h;
 	int start_sample;
 	int num_samples;
@@ -138,6 +146,7 @@ public:
 	int resolution;
 	int offset;
 	int stride;
+	int tile_index;
 
 	device_ptr buffer;
 	device_ptr rng_state;