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, 54 insertions, 0 deletions

diff --git a/intern/cycles/device/device_multi.cpp b/intern/cycles/device/device_multi.cpp
index 624260a81c8..bc505b676fc 100644
--- a/intern/cycles/device/device_multi.cpp
+++ b/intern/cycles/device/device_multi.cpp
@@ -299,6 +299,60 @@ public:
 		return -1;
 	}
 
+	void map_neighbor_tiles(Device *sub_device, RenderTile *tiles)
+	{
+		for(int i = 0; i < 9; i++) {
+			if(!tiles[i].buffers) {
+				continue;
+			}
+			/* If the tile was rendered on another device, copy its memory to
+			 * to the current device now, for the duration of the denoising task.
+			 * Note that this temporarily modifies the RenderBuffers and calls
+			 * the device, so this function is not thread safe. */
+			if(tiles[i].buffers->device != sub_device) {
+				device_vector<float> &mem = tiles[i].buffers->buffer;
+
+				tiles[i].buffers->copy_from_device();
+				device_ptr original_ptr = mem.device_pointer;
+				mem.device_pointer = 0;
+				sub_device->mem_alloc("Temporary memory for neighboring tile", mem, MEM_READ_WRITE);
+				sub_device->mem_copy_to(mem);
+				tiles[i].buffer = mem.device_pointer;
+				mem.device_pointer = original_ptr;
+			}
+		}
+	}
+
+	void unmap_neighbor_tiles(Device * sub_device, RenderTile * tiles)
+	{
+		for(int i = 0; i < 9; i++) {
+			if(!tiles[i].buffers) {
+				continue;
+			}
+			if(tiles[i].buffers->device != sub_device) {
+				device_vector<float> &mem = tiles[i].buffers->buffer;
+
+				device_ptr original_ptr = mem.device_pointer;
+				mem.device_pointer = tiles[i].buffer;
+
+				/* Copy denoised tile to the host. */
+				if(i == 4) {
+					tiles[i].buffers->copy_from_device(sub_device);
+				}
+
+				size_t mem_size = mem.device_size;
+				sub_device->mem_free(mem);
+				mem.device_pointer = original_ptr;
+				mem.device_size = mem_size;
+
+				/* Copy denoised tile to the original device. */
+				if(i == 4) {
+					tiles[i].buffers->device->mem_copy_to(mem);
+				}
+			}
+		}
+	}
+
 	int get_split_task_count(DeviceTask& task)
 	{
 		int total_tasks = 0;