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, 145 insertions, 0 deletions

diff --git a/intern/cycles/device/device_denoising.h b/intern/cycles/device/device_denoising.h
new file mode 100644
index 00000000000..86d8eb64386
--- /dev/null
+++ b/intern/cycles/device/device_denoising.h
@@ -0,0 +1,145 @@
+/*
+ * Copyright 2011-2017 Blender Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef __DEVICE_DENOISING_H__
+#define __DEVICE_DENOISING_H__
+
+#include "device/device.h"
+
+#include "render/buffers.h"
+
+#include "kernel/filter/filter_defines.h"
+
+CCL_NAMESPACE_BEGIN
+
+class DenoisingTask {
+public:
+	/* Parameters of the denoising algorithm. */
+	int radius;
+	float nlm_k_2;
+	float pca_threshold;
+
+	/* Pointer and parameters of the RenderBuffers. */
+	struct RenderBuffers {
+		int denoising_data_offset;
+		int denoising_clean_offset;
+		int pass_stride;
+		int offset;
+		int stride;
+		device_ptr ptr;
+		int samples;
+	} render_buffer;
+
+	TilesInfo *tiles;
+	device_vector<int> tiles_mem;
+	void tiles_from_rendertiles(RenderTile *rtiles);
+
+	int4 rect;
+	int4 filter_area;
+
+	struct DeviceFunctions {
+		function<bool(device_ptr image_ptr,    /* Contains the values that are smoothed. */
+		              device_ptr guide_ptr,    /* Contains the values that are used to calculate weights. */
+		              device_ptr variance_ptr, /* Contains the variance of the guide image. */
+		              device_ptr out_ptr       /* The filtered output is written into this image. */
+		              )> non_local_means;
+		function<bool(device_ptr color_ptr,
+		              device_ptr color_variance_ptr,
+		              device_ptr guide_ptr,
+		              device_ptr guide_variance_ptr,
+		              device_ptr output_ptr
+		              )> reconstruct;
+		function<bool()> construct_transform;
+
+		function<bool(device_ptr a_ptr,
+		              device_ptr b_ptr,
+		              device_ptr mean_ptr,
+		              device_ptr variance_ptr,
+		              int r,
+		              int4 rect
+		              )> combine_halves;
+		function<bool(device_ptr a_ptr,
+		              device_ptr b_ptr,
+		              device_ptr sample_variance_ptr,
+		              device_ptr sv_variance_ptr,
+		              device_ptr buffer_variance_ptr
+		              )> divide_shadow;
+		function<bool(int mean_offset,
+		              int variance_offset,
+		              device_ptr mean_ptr,
+		              device_ptr variance_ptr
+		              )> get_feature;
+		function<bool(device_ptr*)> set_tiles;
+	} functions;
+
+	/* Stores state of the current Reconstruction operation,
+	 * which is accessed by the device in order to perform the operation. */
+	struct ReconstructionState {
+		device_ptr temporary_1_ptr; /* There two images are used as temporary storage. */
+		device_ptr temporary_2_ptr;
+
+		int4 filter_rect;
+		int4 buffer_params;
+
+		int source_w;
+		int source_h;
+	} reconstruction_state;
+
+	/* Stores state of the current NLM operation,
+	 * which is accessed by the device in order to perform the operation. */
+	struct NLMState {
+		device_ptr temporary_1_ptr; /* There three images are used as temporary storage. */
+		device_ptr temporary_2_ptr;
+		device_ptr temporary_3_ptr;
+
+		int r;      /* Search radius of the filter. */
+		int f;      /* Patch size of the filter. */
+		float a;    /* Variance compensation factor in the MSE estimation. */
+		float k_2;  /* Squared value of the k parameter of the filter. */
+
+		void set_parameters(int r_, int f_, float a_, float k_2_) { r = r_; f = f_; a = a_, k_2 = k_2_; }
+	} nlm_state;
+
+	struct Storage {
+		device_only_memory<float>  transform;
+		device_only_memory<int>    rank;
+		device_only_memory<float>  XtWX;
+		device_only_memory<float3> XtWY;
+		int w;
+		int h;
+	} storage;
+
+	DenoisingTask(Device *device) : device(device) {}
+
+	void init_from_devicetask(const DeviceTask &task);
+
+	bool run_denoising();
+
+	struct DenoiseBuffers {
+		int pass_stride;
+		int passes;
+		int w;
+		int h;
+		device_only_memory<float> mem;
+	} buffer;
+
+protected:
+	Device *device;
+};
+
+CCL_NAMESPACE_END
+
+#endif /* __DEVICE_DENOISING_H__ */