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, 152 insertions, 63 deletions

diff --git a/intern/cycles/render/session.cpp b/intern/cycles/render/session.cpp
index c9b5547b407..3eaf34c847f 100644
--- a/intern/cycles/render/session.cpp
+++ b/intern/cycles/render/session.cpp
@@ -114,8 +114,9 @@ Session::~Session()
 	}
 
 	/* clean up */
-	foreach(RenderBuffers *buffers, tile_buffers)
-		delete buffers;
+	foreach(RenderTile &rtile, render_tiles)
+		delete rtile.buffers;
+	tile_manager.free_device();
 
 	delete buffers;
 	delete display;
@@ -268,8 +269,8 @@ void Session::run_gpu()
 			/* update status and timing */
 			update_status_time();
 
-			/* path trace */
-			path_trace();
+			/* render */
+			render();
 
 			device->task_wait();
 
@@ -358,20 +359,22 @@ bool Session::acquire_tile(Device *tile_device, RenderTile& rtile)
 	thread_scoped_lock tile_lock(tile_mutex);
 
 	/* get next tile from manager */
-	Tile tile;
+	Tile *tile;
 	int device_num = device->device_number(tile_device);
 
 	if(!tile_manager.next_tile(tile, device_num))
 		return false;
 	
 	/* fill render tile */
-	rtile.x = tile_manager.state.buffer.full_x + tile.x;
-	rtile.y = tile_manager.state.buffer.full_y + tile.y;
-	rtile.w = tile.w;
-	rtile.h = tile.h;
+	rtile.x = tile_manager.state.buffer.full_x + tile->x;
+	rtile.y = tile_manager.state.buffer.full_y + tile->y;
+	rtile.w = tile->w;
+	rtile.h = tile->h;
 	rtile.start_sample = tile_manager.state.sample;
 	rtile.num_samples = tile_manager.state.num_samples;
 	rtile.resolution = tile_manager.state.resolution_divider;
+	rtile.tile_index = tile->index;
+	rtile.task = (tile->state == Tile::DENOISE)? RenderTile::DENOISE: RenderTile::PATH_TRACE;
 
 	tile_lock.unlock();
 
@@ -383,54 +386,70 @@ bool Session::acquire_tile(Device *tile_device, RenderTile& rtile)
 		rtile.buffer = buffers->buffer.device_pointer;
 		rtile.rng_state = buffers->rng_state.device_pointer;
 		rtile.buffers = buffers;
+		tile->buffers = buffers;
 
 		device->map_tile(tile_device, rtile);
 
 		return true;
 	}
 
-	/* fill buffer parameters */
-	BufferParams buffer_params = tile_manager.params;
-	buffer_params.full_x = rtile.x;
-	buffer_params.full_y = rtile.y;
-	buffer_params.width = rtile.w;
-	buffer_params.height = rtile.h;
-
-	buffer_params.get_offset_stride(rtile.offset, rtile.stride);
-
-	RenderBuffers *tilebuffers;
+	bool store_rtile = false;
+	if(tile->buffers == NULL) {
+		/* fill buffer parameters */
+		BufferParams buffer_params = tile_manager.params;
+		buffer_params.full_x = rtile.x;
+		buffer_params.full_y = rtile.y;
+		buffer_params.width = rtile.w;
+		buffer_params.height = rtile.h;
+
+		/* allocate buffers */
+		if(params.progressive_refine) {
+			tile_lock.lock();
+
+			if(render_tiles.size() == 0) {
+				RenderTile nulltile;
+				nulltile.buffers = NULL;
+				render_tiles.resize(tile_manager.state.num_tiles, nulltile);
+			}
 
-	/* allocate buffers */
-	if(params.progressive_refine) {
-		tile_lock.lock();
+			/* In certain circumstances number of tiles in the tile manager could
+			 * be changed. This is not supported by the progressive refine feature.
+			 */
+			assert(render_tiles.size() == tile_manager.state.num_tiles);
 
-		if(tile_buffers.size() == 0)
-			tile_buffers.resize(tile_manager.state.num_tiles, NULL);
+			RenderTile &stored_rtile = render_tiles[tile->index];
+			if(stored_rtile.buffers == NULL) {
+				tile->buffers = new RenderBuffers(tile_device);
+				tile->buffers->reset(tile_device, buffer_params);
+				store_rtile = true;
+			}
+			else {
+				assert(rtile.x == stored_rtile.x &&
+				       rtile.y == stored_rtile.y &&
+				       rtile.w == stored_rtile.w &&
+				       rtile.h == stored_rtile.h);
+				tile_lock.unlock();
+				tile->buffers = stored_rtile.buffers;
+			}
+		}
+		else {
+			tile->buffers = new RenderBuffers(tile_device);
 
-		/* In certain circumstances number of tiles in the tile manager could
-		 * be changed. This is not supported by the progressive refine feature.
-		 */
-		assert(tile_buffers.size() == tile_manager.state.num_tiles);
+			tile->buffers->reset(tile_device, buffer_params);
+		}
+	}
 
-		tilebuffers = tile_buffers[tile.index];
-		if(tilebuffers == NULL) {
-			tilebuffers = new RenderBuffers(tile_device);
-			tile_buffers[tile.index] = tilebuffers;
+	tile->buffers->params.get_offset_stride(rtile.offset, rtile.stride);
 
-			tilebuffers->reset(tile_device, buffer_params);
-		}
+	rtile.buffer = tile->buffers->buffer.device_pointer;
+	rtile.rng_state = tile->buffers->rng_state.device_pointer;
+	rtile.buffers = tile->buffers;
+	rtile.sample = 0;
 
+	if(store_rtile) {
+		render_tiles[tile->index] = rtile;
 		tile_lock.unlock();
 	}
-	else {
-		tilebuffers = new RenderBuffers(tile_device);
-
-		tilebuffers->reset(tile_device, buffer_params);
-	}
-
-	rtile.buffer = tilebuffers->buffer.device_pointer;
-	rtile.rng_state = tilebuffers->rng_state.device_pointer;
-	rtile.buffers = tilebuffers;
 
 	/* this will tag tile as IN PROGRESS in blender-side render pipeline,
 	 * which is needed to highlight currently rendering tile before first
@@ -449,7 +468,7 @@ void Session::update_tile_sample(RenderTile& rtile)
 		if(params.progressive_refine == false) {
 			/* todo: optimize this by making it thread safe and removing lock */
 
-			update_render_tile_cb(rtile);
+			update_render_tile_cb(rtile, true);
 		}
 	}
 
@@ -462,18 +481,75 @@ void Session::release_tile(RenderTile& rtile)
 
 	progress.add_finished_tile();
 
-	if(write_render_tile_cb) {
-		if(params.progressive_refine == false) {
-			/* todo: optimize this by making it thread safe and removing lock */
-			write_render_tile_cb(rtile);
+	bool delete_tile;
 
-			delete rtile.buffers;
+	if(tile_manager.finish_tile(rtile.tile_index, delete_tile)) {
+		if(write_render_tile_cb && params.progressive_refine == false) {
+			write_render_tile_cb(rtile);
+			if(delete_tile) {
+				delete rtile.buffers;
+				tile_manager.state.tiles[rtile.tile_index].buffers = NULL;
+			}
+		}
+	}
+	else {
+		if(update_render_tile_cb && params.progressive_refine == false) {
+			update_render_tile_cb(rtile, false);
 		}
 	}
 
 	update_status_time();
 }
 
+void Session::map_neighbor_tiles(RenderTile *tiles, Device *tile_device)
+{
+	thread_scoped_lock tile_lock(tile_mutex);
+
+	int center_idx = tiles[4].tile_index;
+	assert(tile_manager.state.tiles[center_idx].state == Tile::DENOISE);
+	BufferParams buffer_params = tile_manager.params;
+	int4 image_region = make_int4(buffer_params.full_x, buffer_params.full_y,
+	                              buffer_params.full_x + buffer_params.width, buffer_params.full_y + buffer_params.height);
+
+	for(int dy = -1, i = 0; dy <= 1; dy++) {
+		for(int dx = -1; dx <= 1; dx++, i++) {
+			int px = tiles[4].x + dx*params.tile_size.x;
+			int py = tiles[4].y + dy*params.tile_size.y;
+			if(px >= image_region.x && py >= image_region.y &&
+			   px <  image_region.z && py <  image_region.w) {
+				int tile_index = center_idx + dy*tile_manager.state.tile_stride + dx;
+				Tile *tile = &tile_manager.state.tiles[tile_index];
+				assert(tile->buffers);
+
+				tiles[i].buffer = tile->buffers->buffer.device_pointer;
+				tiles[i].x = tile_manager.state.buffer.full_x + tile->x;
+				tiles[i].y = tile_manager.state.buffer.full_y + tile->y;
+				tiles[i].w = tile->w;
+				tiles[i].h = tile->h;
+				tiles[i].buffers = tile->buffers;
+
+				tile->buffers->params.get_offset_stride(tiles[i].offset, tiles[i].stride);
+			}
+			else {
+				tiles[i].buffer = (device_ptr)NULL;
+				tiles[i].buffers = NULL;
+				tiles[i].x = clamp(px, image_region.x, image_region.z);
+				tiles[i].y = clamp(py, image_region.y, image_region.w);
+				tiles[i].w = tiles[i].h = 0;
+			}
+		}
+	}
+
+	assert(tiles[4].buffers);
+	device->map_neighbor_tiles(tile_device, tiles);
+}
+
+void Session::unmap_neighbor_tiles(RenderTile *tiles, Device *tile_device)
+{
+	thread_scoped_lock tile_lock(tile_mutex);
+	device->unmap_neighbor_tiles(tile_device, tiles);
+}
+
 void Session::run_cpu()
 {
 	bool tiles_written = false;
@@ -558,8 +634,8 @@ void Session::run_cpu()
 			/* update status and timing */
 			update_status_time();
 
-			/* path trace */
-			path_trace();
+			/* render */
+			render();
 
 			/* update status and timing */
 			update_status_time();
@@ -744,10 +820,10 @@ void Session::reset(BufferParams& buffer_params, int samples)
 	if(params.progressive_refine) {
 		thread_scoped_lock buffers_lock(buffers_mutex);
 
-		foreach(RenderBuffers *buffers, tile_buffers)
-			delete buffers;
+		foreach(RenderTile &rtile, render_tiles)
+			delete rtile.buffers;
 
-		tile_buffers.clear();
+		render_tiles.clear();
 	}
 }
 
@@ -882,13 +958,15 @@ void Session::update_status_time(bool show_pause, bool show_done)
 	progress.set_status(status, substatus);
 }
 
-void Session::path_trace()
+void Session::render()
 {
 	/* add path trace task */
-	DeviceTask task(DeviceTask::PATH_TRACE);
+	DeviceTask task(DeviceTask::RENDER);
 	
 	task.acquire_tile = function_bind(&Session::acquire_tile, this, _1, _2);
 	task.release_tile = function_bind(&Session::release_tile, this, _1);
+	task.map_neighbor_tiles = function_bind(&Session::map_neighbor_tiles, this, _1, _2);
+	task.unmap_neighbor_tiles = function_bind(&Session::unmap_neighbor_tiles, this, _1, _2);
 	task.get_cancel = function_bind(&Progress::get_cancel, &this->progress);
 	task.update_tile_sample = function_bind(&Session::update_tile_sample, this, _1);
 	task.update_progress_sample = function_bind(&Progress::add_samples, &this->progress, _1, _2);
@@ -897,6 +975,18 @@ void Session::path_trace()
 	task.requested_tile_size = params.tile_size;
 	task.passes_size = tile_manager.params.get_passes_size();
 
+	if(params.use_denoising) {
+		task.denoising_radius = params.denoising_radius;
+		task.denoising_strength = params.denoising_strength;
+		task.denoising_feature_strength = params.denoising_feature_strength;
+		task.denoising_relative_pca = params.denoising_relative_pca;
+
+		assert(!scene->film->need_update);
+		task.pass_stride = scene->film->pass_stride;
+		task.pass_denoising_data = scene->film->denoising_data_offset;
+		task.pass_denoising_clean = scene->film->denoising_clean_offset;
+	}
+
 	device->task_add(task);
 }
 
@@ -940,9 +1030,7 @@ bool Session::update_progressive_refine(bool cancel)
 	}
 
 	if(params.progressive_refine) {
-		foreach(RenderBuffers *buffers, tile_buffers) {
-			RenderTile rtile;
-			rtile.buffers = buffers;
+		foreach(RenderTile &rtile, render_tiles) {
 			rtile.sample = sample;
 
 			if(write) {
@@ -951,7 +1039,7 @@ bool Session::update_progressive_refine(bool cancel)
 			}
 			else {
 				if(update_render_tile_cb)
-					update_render_tile_cb(rtile);
+					update_render_tile_cb(rtile, true);
 			}
 		}
 	}
@@ -965,10 +1053,11 @@ void Session::device_free()
 {
 	scene->device_free();
 
-	foreach(RenderBuffers *buffers, tile_buffers)
-		delete buffers;
+	foreach(RenderTile &tile, render_tiles)
+		delete tile.buffers;
+	tile_manager.free_device();
 
-	tile_buffers.clear();
+	render_tiles.clear();
 
 	/* used from background render only, so no need to
 	 * re-create render/display buffers here