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, 55 insertions, 0 deletions

diff --git a/intern/cycles/integrator/adaptive_sampling.h b/intern/cycles/integrator/adaptive_sampling.h
new file mode 100644
index 00000000000..d98edd9894c
--- /dev/null
+++ b/intern/cycles/integrator/adaptive_sampling.h
@@ -0,0 +1,55 @@
+/*
+ * 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.
+ */
+
+#pragma once
+
+CCL_NAMESPACE_BEGIN
+
+class AdaptiveSampling {
+ public:
+  AdaptiveSampling();
+
+  /* Align number of samples so that they align with the adaptive filtering.
+   *
+   * Returns the new value for the `num_samples` so that after rendering so many samples on top
+   * of `start_sample` filtering is required.
+   *
+   * The alignment happens in a way that allows to render as many samples as possible without
+   * missing any filtering point. This means that the result is "clamped" by the nearest sample
+   * at which filtering is needed. This is part of mechanism which ensures that all devices will
+   * perform same exact filtering and adaptive sampling, regardless of their performance.
+   *
+   * `start_sample` is the 0-based index of sample.
+   *
+   * NOTE: The start sample is included into the number of samples to render. This means that
+   * if the number of samples is 1, then the path tracer will render samples [align_samples],
+   * if the number of samples is 2, then the path tracer will render samples [align_samples,
+   * align_samples + 1] and so on. */
+  int align_samples(int start_sample, int num_samples) const;
+
+  /* Check whether adaptive sampling filter should happen at this sample.
+   * Returns false if the adaptive sampling is not use.
+   *
+   * `sample` is the 0-based index of sample. */
+  bool need_filter(int sample) const;
+
+  bool use = false;
+  int adaptive_step = 0;
+  int min_samples = 0;
+  float threshold = 0.0f;
+};
+
+CCL_NAMESPACE_END