Fix adaptive sampling artifacts on tile boundaries

Implement an overscan support for tiles, so that adaptive sampling can
rely on the pixels neighbourhood.

Differential Revision: https://developer.blender.org/D12599

14 files changed, 189 insertions, 70 deletions

diff --git a/intern/cycles/blender/blender_camera.cpp b/intern/cycles/blender/blender_camera.cpp
index 4e8df5a99a6..93f19b73f53 100644
--- a/intern/cycles/blender/blender_camera.cpp
+++ b/intern/cycles/blender/blender_camera.cpp
@@ -927,6 +927,9 @@ BufferParams BlenderSync::get_buffer_params(
     params.height = height;
   }
 
+  params.window_width = params.width;
+  params.window_height = params.height;
+
   return params;
 }
 
diff --git a/intern/cycles/device/optix/device_impl.cpp b/intern/cycles/device/optix/device_impl.cpp
index 49d4e22143f..f9a15553aa9 100644
--- a/intern/cycles/device/optix/device_impl.cpp
+++ b/intern/cycles/device/optix/device_impl.cpp
@@ -768,7 +768,13 @@ void OptiXDevice::denoise_color_read(DenoiseContext &context, const DenoisePass
   destination.num_components = 3;
   destination.pixel_stride = context.buffer_params.pass_stride;
 
-  pass_accessor.get_render_tile_pixels(context.render_buffers, context.buffer_params, destination);
+  BufferParams buffer_params = context.buffer_params;
+  buffer_params.window_x = 0;
+  buffer_params.window_y = 0;
+  buffer_params.window_width = buffer_params.width;
+  buffer_params.window_height = buffer_params.height;
+
+  pass_accessor.get_render_tile_pixels(context.render_buffers, buffer_params, destination);
 }
 
 bool OptiXDevice::denoise_filter_color_preprocess(DenoiseContext &context, const DenoisePass &pass)
diff --git a/intern/cycles/integrator/denoiser_oidn.cpp b/intern/cycles/integrator/denoiser_oidn.cpp
index 7fc2b2b1892..ee3b62668a7 100644
--- a/intern/cycles/integrator/denoiser_oidn.cpp
+++ b/intern/cycles/integrator/denoiser_oidn.cpp
@@ -289,7 +289,13 @@ class OIDNDenoiseContext {
      * pixels. */
     const PassAccessorCPU pass_accessor(pass_access_info, 1.0f, num_samples_);
 
-    pass_accessor.get_render_tile_pixels(render_buffers_, buffer_params_, destination);
+    BufferParams buffer_params = buffer_params_;
+    buffer_params.window_x = 0;
+    buffer_params.window_y = 0;
+    buffer_params.window_width = buffer_params.width;
+    buffer_params.window_height = buffer_params.height;
+
+    pass_accessor.get_render_tile_pixels(render_buffers_, buffer_params, destination);
   }
 
   /* Read pass pixels using PassAccessor into a temporary buffer which is owned by the pass.. */
diff --git a/intern/cycles/integrator/pass_accessor_cpu.cpp b/intern/cycles/integrator/pass_accessor_cpu.cpp
index 3c6691f6d43..80908271ff6 100644
--- a/intern/cycles/integrator/pass_accessor_cpu.cpp
+++ b/intern/cycles/integrator/pass_accessor_cpu.cpp
@@ -99,17 +99,22 @@ inline void PassAccessorCPU::run_get_pass_kernel_processor_float(
 {
   DCHECK_EQ(destination.stride, 0) << "Custom stride for float destination is not implemented.";
 
-  const float *buffer_data = render_buffers->buffer.data();
+  const int64_t pass_stride = buffer_params.pass_stride;
+  const int64_t buffer_row_stride = buffer_params.stride * buffer_params.pass_stride;
+
+  const float *window_data = render_buffers->buffer.data() + buffer_params.window_x * pass_stride +
+                             buffer_params.window_y * buffer_row_stride;
+
   const int pixel_stride = destination.pixel_stride ? destination.pixel_stride :
                                                       destination.num_components;
 
-  tbb::parallel_for(0, buffer_params.height, [&](int64_t y) {
-    int64_t pixel_index = y * buffer_params.width;
-    for (int64_t x = 0; x < buffer_params.width; ++x, ++pixel_index) {
-      const int64_t input_pixel_offset = pixel_index * buffer_params.pass_stride;
-      const float *buffer = buffer_data + input_pixel_offset;
-      float *pixel = destination.pixels + (pixel_index + destination.offset) * pixel_stride;
+  tbb::parallel_for(0, buffer_params.window_height, [&](int64_t y) {
+    const float *buffer = window_data + y * buffer_row_stride;
+    float *pixel = destination.pixels +
+                   (y * buffer_params.width + destination.offset) * pixel_stride;
 
+    for (int64_t x = 0; x < buffer_params.window_width;
+         ++x, buffer += pass_stride, pixel += pixel_stride) {
       processor(kfilm_convert, buffer, pixel);
     }
   });
@@ -123,26 +128,28 @@ inline void PassAccessorCPU::run_get_pass_kernel_processor_half_rgba(
     const Destination &destination,
     const Processor &processor) const
 {
-  const float *buffer_data = render_buffers->buffer.data();
+  const int64_t pass_stride = buffer_params.pass_stride;
+  const int64_t buffer_row_stride = buffer_params.stride * buffer_params.pass_stride;
+
+  const float *window_data = render_buffers->buffer.data() + buffer_params.window_x * pass_stride +
+                             buffer_params.window_y * buffer_row_stride;
 
   half4 *dst_start = destination.pixels_half_rgba + destination.offset;
   const int destination_stride = destination.stride != 0 ? destination.stride :
                                                            buffer_params.width;
 
-  tbb::parallel_for(0, buffer_params.height, [&](int64_t y) {
-    int64_t pixel_index = y * buffer_params.width;
-    half4 *dst_row_start = dst_start + y * destination_stride;
-    for (int64_t x = 0; x < buffer_params.width; ++x, ++pixel_index) {
-      const int64_t input_pixel_offset = pixel_index * buffer_params.pass_stride;
-      const float *buffer = buffer_data + input_pixel_offset;
+  tbb::parallel_for(0, buffer_params.window_height, [&](int64_t y) {
+    const float *buffer = window_data + y * buffer_row_stride;
+    half4 *pixel = dst_start + y * destination_stride;
+    for (int64_t x = 0; x < buffer_params.window_width; ++x, buffer += pass_stride, ++pixel) {
 
-      float pixel[4];
-      processor(kfilm_convert, buffer, pixel);
+      float pixel_rgba[4];
+      processor(kfilm_convert, buffer, pixel_rgba);
 
-      film_apply_pass_pixel_overlays_rgba(kfilm_convert, buffer, pixel);
+      film_apply_pass_pixel_overlays_rgba(kfilm_convert, buffer, pixel_rgba);
 
-      half4 *pixel_half_rgba = dst_row_start + x;
-      float4_store_half(&pixel_half_rgba->x, make_float4(pixel[0], pixel[1], pixel[2], pixel[3]));
+      float4_store_half(&pixel->x,
+                        make_float4(pixel_rgba[0], pixel_rgba[1], pixel_rgba[2], pixel_rgba[3]));
     }
   });
 }
diff --git a/intern/cycles/integrator/pass_accessor_gpu.cpp b/intern/cycles/integrator/pass_accessor_gpu.cpp
index eb80ba99655..7b01d061708 100644
--- a/intern/cycles/integrator/pass_accessor_gpu.cpp
+++ b/intern/cycles/integrator/pass_accessor_gpu.cpp
@@ -43,10 +43,13 @@ void PassAccessorGPU::run_film_convert_kernels(DeviceKernel kernel,
   KernelFilmConvert kfilm_convert;
   init_kernel_film_convert(&kfilm_convert, buffer_params, destination);
 
-  const int work_size = buffer_params.width * buffer_params.height;
+  const int work_size = buffer_params.window_width * buffer_params.window_height;
 
   const int destination_stride = destination.stride != 0 ? destination.stride :
-                                                           buffer_params.width;
+                                                           buffer_params.window_width;
+
+  const int offset = buffer_params.window_x * buffer_params.pass_stride +
+                     buffer_params.window_y * buffer_params.stride * buffer_params.pass_stride;
 
   if (destination.d_pixels) {
     DCHECK_EQ(destination.stride, 0) << "Custom stride for float destination is not implemented.";
@@ -55,8 +58,8 @@ void PassAccessorGPU::run_film_convert_kernels(DeviceKernel kernel,
                     const_cast<device_ptr *>(&destination.d_pixels),
                     const_cast<device_ptr *>(&render_buffers->buffer.device_pointer),
                     const_cast<int *>(&work_size),
-                    const_cast<int *>(&buffer_params.width),
-                    const_cast<int *>(&buffer_params.offset),
+                    const_cast<int *>(&buffer_params.window_width),
+                    const_cast<int *>(&offset),
                     const_cast<int *>(&buffer_params.stride),
                     const_cast<int *>(&destination.offset),
                     const_cast<int *>(&destination_stride)};
@@ -70,8 +73,8 @@ void PassAccessorGPU::run_film_convert_kernels(DeviceKernel kernel,
                     const_cast<device_ptr *>(&destination.d_pixels_half_rgba),
                     const_cast<device_ptr *>(&render_buffers->buffer.device_pointer),
                     const_cast<int *>(&work_size),
-                    const_cast<int *>(&buffer_params.width),
-                    const_cast<int *>(&buffer_params.offset),
+                    const_cast<int *>(&buffer_params.window_width),
+                    const_cast<int *>(&offset),
                     const_cast<int *>(&buffer_params.stride),
                     const_cast<int *>(&destination.offset),
                     const_cast<int *>(&destination_stride)};
diff --git a/intern/cycles/integrator/path_trace.cpp b/intern/cycles/integrator/path_trace.cpp
index 7624b244175..3ea5c3c64b8 100644
--- a/intern/cycles/integrator/path_trace.cpp
+++ b/intern/cycles/integrator/path_trace.cpp
@@ -282,6 +282,12 @@ static BufferParams scale_buffer_params(const BufferParams &params, int resoluti
 
   scaled_params.width = max(1, params.width / resolution_divider);
   scaled_params.height = max(1, params.height / resolution_divider);
+
+  scaled_params.window_x = params.window_x / resolution_divider;
+  scaled_params.window_y = params.window_y / resolution_divider;
+  scaled_params.window_width = params.window_width / resolution_divider;
+  scaled_params.window_height = params.window_height / resolution_divider;
+
   scaled_params.full_x = params.full_x / resolution_divider;
   scaled_params.full_y = params.full_y / resolution_divider;
   scaled_params.full_width = params.full_width / resolution_divider;
@@ -1005,12 +1011,12 @@ bool PathTrace::set_render_tile_pixels(PassAccessor &pass_accessor,
 int2 PathTrace::get_render_tile_size() const
 {
   if (full_frame_state_.render_buffers) {
-    return make_int2(full_frame_state_.render_buffers->params.width,
-                     full_frame_state_.render_buffers->params.height);
+    return make_int2(full_frame_state_.render_buffers->params.window_width,
+                     full_frame_state_.render_buffers->params.window_height);
   }
 
   const Tile &tile = tile_manager_.get_current_tile();
-  return make_int2(tile.width, tile.height);
+  return make_int2(tile.window_width, tile.window_height);
 }
 
 int2 PathTrace::get_render_tile_offset() const
@@ -1020,7 +1026,7 @@ int2 PathTrace::get_render_tile_offset() const
   }
 
   const Tile &tile = tile_manager_.get_current_tile();
-  return make_int2(tile.x, tile.y);
+  return make_int2(tile.x + tile.window_x, tile.y + tile.window_y);
 }
 
 int2 PathTrace::get_render_size() const
diff --git a/intern/cycles/integrator/path_trace_work.cpp b/intern/cycles/integrator/path_trace_work.cpp
index c29177907c9..f626beb0aaa 100644
--- a/intern/cycles/integrator/path_trace_work.cpp
+++ b/intern/cycles/integrator/path_trace_work.cpp
@@ -191,8 +191,10 @@ PassAccessor::Destination PathTraceWork::get_display_destination_template(
   PassAccessor::Destination destination(film_->get_display_pass());
 
   const int2 display_texture_size = display->get_texture_size();
-  const int texture_x = effective_buffer_params_.full_x - effective_full_params_.full_x;
-  const int texture_y = effective_buffer_params_.full_y - effective_full_params_.full_y;
+  const int texture_x = effective_buffer_params_.full_x - effective_full_params_.full_x +
+                        effective_buffer_params_.window_x;
+  const int texture_y = effective_buffer_params_.full_y - effective_full_params_.full_y +
+                        effective_buffer_params_.window_y;
 
   destination.offset = texture_y * display_texture_size.x + texture_x;
   destination.stride = display_texture_size.x;
diff --git a/intern/cycles/integrator/path_trace_work_gpu.cpp b/intern/cycles/integrator/path_trace_work_gpu.cpp
index 7babc9d09fa..c29b0fb039e 100644
--- a/intern/cycles/integrator/path_trace_work_gpu.cpp
+++ b/intern/cycles/integrator/path_trace_work_gpu.cpp
@@ -737,13 +737,13 @@ void PathTraceWorkGPU::copy_to_display_naive(PathTraceDisplay *display,
 {
   const int full_x = effective_buffer_params_.full_x;
   const int full_y = effective_buffer_params_.full_y;
-  const int width = effective_buffer_params_.width;
-  const int height = effective_buffer_params_.height;
-  const int final_width = buffers_->params.width;
-  const int final_height = buffers_->params.height;
+  const int width = effective_buffer_params_.window_width;
+  const int height = effective_buffer_params_.window_height;
+  const int final_width = buffers_->params.window_width;
+  const int final_height = buffers_->params.window_height;
 
-  const int texture_x = full_x - effective_full_params_.full_x;
-  const int texture_y = full_y - effective_full_params_.full_y;
+  const int texture_x = full_x - effective_full_params_.full_x + effective_buffer_params_.window_x;
+  const int texture_y = full_y - effective_full_params_.full_y + effective_buffer_params_.window_y;
 
   /* Re-allocate display memory if needed, and make sure the device pointer is allocated.
    *
diff --git a/intern/cycles/kernel/device/gpu/kernel.h b/intern/cycles/kernel/device/gpu/kernel.h
index 7b79c0aedfa..3379114fc62 100644
--- a/intern/cycles/kernel/device/gpu/kernel.h
+++ b/intern/cycles/kernel/device/gpu/kernel.h
@@ -424,8 +424,12 @@ ccl_device_inline void kernel_gpu_film_convert_common(const KernelFilmConvert *k
     return;
   }
 
-  const uint64_t render_buffer_offset = (uint64_t)render_pixel_index * kfilm_convert->pass_stride;
-  ccl_global const float *buffer = render_buffer + render_buffer_offset;
+  const int x = render_pixel_index % width;
+  const int y = render_pixel_index / width;
+
+  ccl_global const float *buffer = render_buffer + offset + x * kfilm_convert->pass_stride +
+                                   y * stride * kfilm_convert->pass_stride;
+
   ccl_global float *pixel = pixels +
                             (render_pixel_index + dst_offset) * kfilm_convert->pixel_stride;
 
@@ -451,17 +455,17 @@ ccl_device_inline void kernel_gpu_film_convert_half_rgba_common_rgba(
     return;
   }
 
-  const uint64_t render_buffer_offset = (uint64_t)render_pixel_index * kfilm_convert->pass_stride;
-  ccl_global const float *buffer = render_buffer + render_buffer_offset;
+  const int x = render_pixel_index % width;
+  const int y = render_pixel_index / width;
+
+  ccl_global const float *buffer = render_buffer + offset + x * kfilm_convert->pass_stride +
+                                   y * stride * kfilm_convert->pass_stride;
 
   float pixel[4];
   processor(kfilm_convert, buffer, pixel);
 
   film_apply_pass_pixel_overlays_rgba(kfilm_convert, buffer, pixel);
 
-  const int x = render_pixel_index % width;
-  const int y = render_pixel_index / width;
-
   ccl_global half4 *out = ((ccl_global half4 *)rgba) + rgba_offset + y * rgba_stride + x;
   float4_store_half((ccl_global half *)out, make_float4(pixel[0], pixel[1], pixel[2], pixel[3]));
 }
diff --git a/intern/cycles/render/buffers.cpp b/intern/cycles/render/buffers.cpp
index 3682b55049a..00b4284c22b 100644
--- a/intern/cycles/render/buffers.cpp
+++ b/intern/cycles/render/buffers.cpp
@@ -97,6 +97,11 @@ NODE_DEFINE(BufferParams)
   SOCKET_INT(width, "Width", 0);
   SOCKET_INT(height, "Height", 0);
 
+  SOCKET_INT(window_x, "Window X", 0);
+  SOCKET_INT(window_y, "Window Y", 0);
+  SOCKET_INT(window_width, "Window Width", 0);
+  SOCKET_INT(window_height, "Window Height", 0);
+
   SOCKET_INT(full_x, "Full X", 0);
   SOCKET_INT(full_y, "Full Y", 0);
   SOCKET_INT(full_width, "Full Width", 0);
@@ -233,13 +238,31 @@ void BufferParams::update_offset_stride()
 
 bool BufferParams::modified(const BufferParams &other) const
 {
-  if (!(width == other.width && height == other.height && full_x == other.full_x &&
-        full_y == other.full_y && full_width == other.full_width &&
-        full_height == other.full_height && offset == other.offset && stride == other.stride &&
-        pass_stride == other.pass_stride && layer == other.layer && view == other.view &&
-        exposure == other.exposure &&
-        use_approximate_shadow_catcher == other.use_approximate_shadow_catcher &&
-        use_transparent_background == other.use_transparent_background)) {
+  if (width != other.width || height != other.height) {
+    return true;
+  }
+
+  if (full_x != other.full_x || full_y != other.full_y || full_width != other.full_width ||
+      full_height != other.full_height) {
+    return true;
+  }
+
+  if (window_x != other.window_x || window_y != other.window_y ||
+      window_width != other.window_width || window_height != other.window_height) {
+    return true;
+  }
+
+  if (offset != other.offset || stride != other.stride || pass_stride != other.pass_stride) {
+    return true;
+  }
+
+  if (layer != other.layer || view != other.view) {
+    return false;
+  }
+
+  if (exposure != other.exposure ||
+      use_approximate_shadow_catcher != other.use_approximate_shadow_catcher ||
+      use_transparent_background != other.use_transparent_background) {
     return true;
   }
 
diff --git a/intern/cycles/render/buffers.h b/intern/cycles/render/buffers.h
index 184ac7197af..3cf826f14d6 100644
--- a/intern/cycles/render/buffers.h
+++ b/intern/cycles/render/buffers.h
@@ -82,6 +82,15 @@ class BufferParams : public Node {
   int width = 0;
   int height = 0;
 
+  /* Windows defines which part of the buffers is visible. The part outside of the window is
+   * considered an "overscan".
+   *
+   * Window X and Y are relative to the position of the buffer in the full buffer. */
+  int window_x = 0;
+  int window_y = 0;
+  int window_width = 0;
+  int window_height = 0;
+
   /* Offset into and width/height of the full buffer. */
   int full_x = 0;
   int full_y = 0;
diff --git a/intern/cycles/render/session.cpp b/intern/cycles/render/session.cpp
index 4f93c3a9054..8d2d950f661 100644
--- a/intern/cycles/render/session.cpp
+++ b/intern/cycles/render/session.cpp
@@ -286,12 +286,20 @@ RenderWork Session::run_update_for_next_iteration()
       BufferParams tile_params = buffer_params_;
 
       const Tile &tile = tile_manager_.get_current_tile();
+
       tile_params.width = tile.width;
       tile_params.height = tile.height;
+
+      tile_params.window_x = tile.window_x;
+      tile_params.window_y = tile.window_y;
+      tile_params.window_width = tile.window_width;
+      tile_params.window_height = tile.window_height;
+
       tile_params.full_x = tile.x + buffer_params_.full_x;
       tile_params.full_y = tile.y + buffer_params_.full_y;
       tile_params.full_width = buffer_params_.full_width;
       tile_params.full_height = buffer_params_.full_height;
+
       tile_params.update_offset_stride();
 
       path_trace_->reset(buffer_params_, tile_params);
diff --git a/intern/cycles/render/tile.cpp b/intern/cycles/render/tile.cpp
index 7e53a9d0911..75c1f78982d 100644
--- a/intern/cycles/render/tile.cpp
+++ b/intern/cycles/render/tile.cpp
@@ -372,8 +372,17 @@ void TileManager::update(const BufferParams &params, const Scene *scene)
   configure_image_spec_from_buffer(&write_state_.image_spec, buffer_params_, tile_size_);
 
   const DenoiseParams denoise_params = scene->integrator->get_denoise_params();
+  const AdaptiveSampling adaptive_sampling = scene->integrator->get_adaptive_sampling();
+
   node_to_image_spec_atttributes(
       &write_state_.image_spec, &denoise_params, ATTR_DENOISE_SOCKET_PREFIX);
+
+  if (adaptive_sampling.use) {
+    overscan_ = 4;
+  }
+  else {
+    overscan_ = 0;
+  }
 }
 
 bool TileManager::done()
@@ -399,19 +408,29 @@ Tile TileManager::get_tile_for_index(int index) const
   /* TODO(sergey): Consider using hilbert spiral, or. maybe, even configurable. Not sure this
    * brings a lot of value since this is only applicable to BIG tiles. */
 
-  const int tile_y = index / tile_state_.num_tiles_x;
-  const int tile_x = index - tile_y * tile_state_.num_tiles_x;
+  const int tile_index_y = index / tile_state_.num_tiles_x;
+  const int tile_index_x = index - tile_index_y * tile_state_.num_tiles_x;
+
+  const int tile_x = tile_index_x * tile_size_.x;
+  const int tile_y = tile_index_y * tile_size_.y;
 
   Tile tile;
 
-  tile.x = tile_x * tile_size_.x;
-  tile.y = tile_y * tile_size_.y;
-  tile.width = tile_size_.x;
-  tile.height = tile_size_.y;
+  tile.x = tile_x - overscan_;
+  tile.y = tile_y - overscan_;
+  tile.width = tile_size_.x + 2 * overscan_;
+  tile.height = tile_size_.y + 2 * overscan_;
 
+  tile.x = max(tile.x, 0);
+  tile.y = max(tile.y, 0);
   tile.width = min(tile.width, buffer_params_.width - tile.x);
   tile.height = min(tile.height, buffer_params_.height - tile.y);
 
+  tile.window_x = tile_x - tile.x;
+  tile.window_y = tile_y - tile.y;
+  tile.window_width = min(tile_size_.x, buffer_params_.width - (tile.x + tile.window_x));
+  tile.window_height = min(tile_size_.y, buffer_params_.height - (tile.y + tile.window_y));
+
   return tile;
 }
 
@@ -483,11 +502,22 @@ bool TileManager::write_tile(const RenderBuffers &tile_buffers)
 
   DCHECK_EQ(tile_buffers.params.pass_stride, buffer_params_.pass_stride);
 
+  vector<float> pixel_storage;
+
   const BufferParams &tile_params = tile_buffers.params;
 
-  const float *pixels = tile_buffers.buffer.data();
-  const int tile_x = tile_params.full_x - buffer_params_.full_x;
-  const int tile_y = tile_params.full_y - buffer_params_.full_y;
+  const int tile_x = tile_params.full_x - buffer_params_.full_x + tile_params.window_x;
+  const int tile_y = tile_params.full_y - buffer_params_.full_y + tile_params.window_y;
+
+  const int64_t pass_stride = tile_params.pass_stride;
+  const int64_t tile_row_stride = tile_params.width * pass_stride;
+
+  const int64_t xstride = pass_stride * sizeof(float);
+  const int64_t ystride = xstride * tile_params.width;
+  const int64_t zstride = ystride * tile_params.height;
+
+  const float *pixels = tile_buffers.buffer.data() + tile_params.window_x * pass_stride +
+                        tile_params.window_y * tile_row_stride;
 
   VLOG(3) << "Write tile at " << tile_x << ", " << tile_y;
 
@@ -499,13 +529,16 @@ bool TileManager::write_tile(const RenderBuffers &tile_buffers)
    * The only thing we have to ensure is that the tile_x and tile_y are a multiple of the
    * image tile size, which happens in compute_render_tile_size. */
   if (!write_state_.tile_out->write_tiles(tile_x,
-                                          tile_x + tile_params.width,
+                                          tile_x + tile_params.window_width,
                                           tile_y,
-                                          tile_y + tile_params.height,
+                                          tile_y + tile_params.window_height,
                                           0,
                                           1,
                                           TypeDesc::FLOAT,
-                                          pixels)) {
+                                          pixels,
+                                          xstride,
+                                          ystride,
+                                          zstride)) {
     LOG(ERROR) << "Error writing tile " << write_state_.tile_out->geterror();
     return false;
   }
@@ -531,12 +564,15 @@ void TileManager::finish_write_tiles()
          ++tile_index) {
       const Tile tile = get_tile_for_index(tile_index);
 
-      VLOG(3) << "Write dummy tile at " << tile.x << ", " << tile.y;
+      const int tile_x = tile.x + tile.window_x;
+      const int tile_y = tile.y + tile.window_y;
+
+      VLOG(3) << "Write dummy tile at " << tile_x << ", " << tile_y;
 
-      write_state_.tile_out->write_tiles(tile.x,
-                                         tile.x + tile.width,
-                                         tile.y,
-                                         tile.y + tile.height,
+      write_state_.tile_out->write_tiles(tile_x,
+                                         tile_x + tile.window_width,
+                                         tile_y,
+                                         tile_y + tile.window_height,
                                          0,
                                          1,
                                          TypeDesc::FLOAT,
diff --git a/intern/cycles/render/tile.h b/intern/cycles/render/tile.h
index 08eaa4034f0..a13afaea64e 100644
--- a/intern/cycles/render/tile.h
+++ b/intern/cycles/render/tile.h
@@ -35,6 +35,9 @@ class Tile {
   int x = 0, y = 0;
   int width = 0, height = 0;
 
+  int window_x = 0, window_y = 0;
+  int window_width = 0, window_height = 0;
+
   Tile()
   {
   }
@@ -128,6 +131,9 @@ class TileManager {
 
   int2 tile_size_ = make_int2(0, 0);
 
+  /* Number of extra pixels around the actual tile to render. */
+  int overscan_ = 0;
+
   BufferParams buffer_params_;
 
   /* Tile scheduling state. */