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, 33 insertions, 21 deletions

diff --git a/intern/cycles/device/opencl/opencl_mega.cpp b/intern/cycles/device/opencl/opencl_mega.cpp
index a2fd1d71156..06c15bcf401 100644
--- a/intern/cycles/device/opencl/opencl_mega.cpp
+++ b/intern/cycles/device/opencl/opencl_mega.cpp
@@ -108,41 +108,53 @@ public:
 		else if(task->type == DeviceTask::SHADER) {
 			shader(*task);
 		}
-		else if(task->type == DeviceTask::PATH_TRACE) {
+		else if(task->type == DeviceTask::RENDER) {
 			RenderTile tile;
 			/* Keep rendering tiles until done. */
 			while(task->acquire_tile(this, tile)) {
-				int start_sample = tile.start_sample;
-				int end_sample = tile.start_sample + tile.num_samples;
+				if(tile.task == RenderTile::PATH_TRACE) {
+					int start_sample = tile.start_sample;
+					int end_sample = tile.start_sample + tile.num_samples;
 
-				for(int sample = start_sample; sample < end_sample; sample++) {
-					if(task->get_cancel()) {
-						if(task->need_finish_queue == false)
-							break;
-					}
+					for(int sample = start_sample; sample < end_sample; sample++) {
+						if(task->get_cancel()) {
+							if(task->need_finish_queue == false)
+								break;
+						}
+
+						path_trace(tile, sample);
 
-					path_trace(tile, sample);
+						tile.sample = sample + 1;
 
-					tile.sample = sample + 1;
+						task->update_progress(&tile, tile.w*tile.h);
+					}
 
+					/* Complete kernel execution before release tile */
+					/* This helps in multi-device render;
+					 * The device that reaches the critical-section function
+					 * release_tile waits (stalling other devices from entering
+					 * release_tile) for all kernels to complete. If device1 (a
+					 * slow-render device) reaches release_tile first then it would
+					 * stall device2 (a fast-render device) from proceeding to render
+					 * next tile.
+					 */
+					clFinish(cqCommandQueue);
+				}
+				else if(tile.task == RenderTile::DENOISE) {
+					tile.sample = tile.start_sample + tile.num_samples;
+					denoise(tile, *task);
 					task->update_progress(&tile, tile.w*tile.h);
 				}
 
-				/* Complete kernel execution before release tile */
-				/* This helps in multi-device render;
-				 * The device that reaches the critical-section function
-				 * release_tile waits (stalling other devices from entering
-				 * release_tile) for all kernels to complete. If device1 (a
-				 * slow-render device) reaches release_tile first then it would
-				 * stall device2 (a fast-render device) from proceeding to render
-				 * next tile.
-				 */
-				clFinish(cqCommandQueue);
-
 				task->release_tile(tile);
 			}
 		}
 	}
+
+	bool is_split_kernel()
+	{
+		return false;
+	}
 };
 
 Device *opencl_create_mega_device(DeviceInfo& info, Stats& stats, bool background)