Cycles: merge of cycles-x branch, a major update to the renderer

This includes much improved GPU rendering performance, viewport interactivity,
new shadow catcher, revamped sampling settings, subsurface scattering anisotropy,
new GPU volume sampling, improved PMJ sampling pattern, and more.

Some features have also been removed or changed, breaking backwards compatibility.
Including the removal of the OpenCL backend, for which alternatives are under
development.

Release notes and code docs:
https://wiki.blender.org/wiki/Reference/Release_Notes/3.0/Cycles
https://wiki.blender.org/wiki/Source/Render/Cycles

Credits:
* Sergey Sharybin
* Brecht Van Lommel
* Patrick Mours (OptiX backend)
* Christophe Hery (subsurface scattering anisotropy)
* William Leeson (PMJ sampling pattern)
* Alaska (various fixes and tweaks)
* Thomas Dinges (various fixes)

For the full commit history, see the cycles-x branch. This squashes together
all the changes since intermediate changes would often fail building or tests.

Ref T87839, T87837, T87836
Fixes T90734, T89353, T80267, T80267, T77185, T69800

1 files changed, 138 insertions, 0 deletions

diff --git a/intern/cycles/integrator/work_tile_scheduler.cpp b/intern/cycles/integrator/work_tile_scheduler.cpp
new file mode 100644
index 00000000000..3fc99d5b74d
--- /dev/null
+++ b/intern/cycles/integrator/work_tile_scheduler.cpp
@@ -0,0 +1,138 @@
+/*
+ * Copyright 2011-2021 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.
+ */
+
+#include "integrator/work_tile_scheduler.h"
+
+#include "device/device_queue.h"
+#include "integrator/tile.h"
+#include "render/buffers.h"
+#include "util/util_atomic.h"
+#include "util/util_logging.h"
+
+CCL_NAMESPACE_BEGIN
+
+WorkTileScheduler::WorkTileScheduler()
+{
+}
+
+void WorkTileScheduler::set_max_num_path_states(int max_num_path_states)
+{
+  max_num_path_states_ = max_num_path_states;
+}
+
+void WorkTileScheduler::reset(const BufferParams &buffer_params, int sample_start, int samples_num)
+{
+  /* Image buffer parameters. */
+  image_full_offset_px_.x = buffer_params.full_x;
+  image_full_offset_px_.y = buffer_params.full_y;
+
+  image_size_px_ = make_int2(buffer_params.width, buffer_params.height);
+
+  offset_ = buffer_params.offset;
+  stride_ = buffer_params.stride;
+
+  /* Samples parameters. */
+  sample_start_ = sample_start;
+  samples_num_ = samples_num;
+
+  /* Initialize new scheduling. */
+  reset_scheduler_state();
+}
+
+void WorkTileScheduler::reset_scheduler_state()
+{
+  tile_size_ = tile_calculate_best_size(image_size_px_, samples_num_, max_num_path_states_);
+
+  VLOG(3) << "Will schedule tiles of size " << tile_size_;
+
+  if (VLOG_IS_ON(3)) {
+    /* The logging is based on multiple tiles scheduled, ignoring overhead of multi-tile scheduling
+     * and purely focusing on the number of used path states. */
+    const int num_path_states_in_tile = tile_size_.width * tile_size_.height *
+                                        tile_size_.num_samples;
+    const int num_tiles = max_num_path_states_ / num_path_states_in_tile;
+    VLOG(3) << "Number of unused path states: "
+            << max_num_path_states_ - num_tiles * num_path_states_in_tile;
+  }
+
+  num_tiles_x_ = divide_up(image_size_px_.x, tile_size_.width);
+  num_tiles_y_ = divide_up(image_size_px_.y, tile_size_.height);
+
+  total_tiles_num_ = num_tiles_x_ * num_tiles_y_;
+  num_tiles_per_sample_range_ = divide_up(samples_num_, tile_size_.num_samples);
+
+  next_work_index_ = 0;
+  total_work_size_ = total_tiles_num_ * num_tiles_per_sample_range_;
+}
+
+bool WorkTileScheduler::get_work(KernelWorkTile *work_tile_, const int max_work_size)
+{
+  /* Note that the `max_work_size` can be higher than the `max_num_path_states_`: this is because
+   * the path trace work can decice to use smaller tile sizes and greedily schedule multiple tiles,
+   * improving overall device occupancy.
+   * So the `max_num_path_states_` is a "scheduling unit", and the `max_work_size` is a "scheduling
+   * limit". */
+
+  DCHECK_NE(max_num_path_states_, 0);
+
+  const int work_index = atomic_fetch_and_add_int32(&next_work_index_, 1);
+  if (work_index >= total_work_size_) {
+    return false;
+  }
+
+  const int sample_range_index = work_index % num_tiles_per_sample_range_;
+  const int start_sample = sample_range_index * tile_size_.num_samples;
+  const int tile_index = work_index / num_tiles_per_sample_range_;
+  const int tile_y = tile_index / num_tiles_x_;
+  const int tile_x = tile_index - tile_y * num_tiles_x_;
+
+  KernelWorkTile work_tile;
+  work_tile.x = tile_x * tile_size_.width;
+  work_tile.y = tile_y * tile_size_.height;
+  work_tile.w = tile_size_.width;
+  work_tile.h = tile_size_.height;
+  work_tile.start_sample = sample_start_ + start_sample;
+  work_tile.num_samples = min(tile_size_.num_samples, samples_num_ - start_sample);
+  work_tile.offset = offset_;
+  work_tile.stride = stride_;
+
+  work_tile.w = min(work_tile.w, image_size_px_.x - work_tile.x);
+  work_tile.h = min(work_tile.h, image_size_px_.y - work_tile.y);
+
+  work_tile.x += image_full_offset_px_.x;
+  work_tile.y += image_full_offset_px_.y;
+
+  const int tile_work_size = work_tile.w * work_tile.h * work_tile.num_samples;
+
+  DCHECK_GT(tile_work_size, 0);
+
+  if (max_work_size && tile_work_size > max_work_size) {
+    /* The work did not fit into the requested limit of the work size. Unschedule the tile,
+     * allowing others (or ourselves later one) to pick it up.
+     *
+     * TODO: Such temporary decrement is not ideal, since it might lead to situation when another
+     * device sees there is nothing to be done, finishing its work and leaving all work to be
+     * done by us. */
+    atomic_fetch_and_add_int32(&next_work_index_, -1);
+    return false;
+  }
+
+  *work_tile_ = work_tile;
+
+  return true;
+}
+
+CCL_NAMESPACE_END