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, 116 insertions, 0 deletions

diff --git a/intern/cycles/kernel/kernel_shadow_catcher.h b/intern/cycles/kernel/kernel_shadow_catcher.h
new file mode 100644
index 00000000000..824749818a4
--- /dev/null
+++ b/intern/cycles/kernel/kernel_shadow_catcher.h
@@ -0,0 +1,116 @@
+/*
+ * 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
+
+#include "kernel/integrator/integrator_state_util.h"
+#include "kernel/kernel_path_state.h"
+
+CCL_NAMESPACE_BEGIN
+
+/* Check whether current surface bounce is where path is to be split for the shadow catcher. */
+ccl_device_inline bool kernel_shadow_catcher_is_path_split_bounce(INTEGRATOR_STATE_ARGS,
+                                                                  const int object_flag)
+{
+#ifdef __SHADOW_CATCHER__
+  if (!kernel_data.integrator.has_shadow_catcher) {
+    return false;
+  }
+
+  /* Check the flag first, avoiding fetches form global memory. */
+  if ((object_flag & SD_OBJECT_SHADOW_CATCHER) == 0) {
+    return false;
+  }
+  if (object_flag & SD_OBJECT_HOLDOUT_MASK) {
+    return false;
+  }
+
+  const int path_flag = INTEGRATOR_STATE(path, flag);
+
+  if ((path_flag & PATH_RAY_TRANSPARENT_BACKGROUND) == 0) {
+    /* Split only on primary rays, secondary bounces are to treat shadow catcher as a regular
+     * object. */
+    return false;
+  }
+
+  if (path_flag & PATH_RAY_SHADOW_CATCHER_PASS) {
+    return false;
+  }
+
+  return true;
+#else
+  (void)object_flag;
+  return false;
+#endif
+}
+
+/* Check whether the current path can still split. */
+ccl_device_inline bool kernel_shadow_catcher_path_can_split(INTEGRATOR_STATE_CONST_ARGS)
+{
+  if (INTEGRATOR_PATH_IS_TERMINATED && INTEGRATOR_SHADOW_PATH_IS_TERMINATED) {
+    return false;
+  }
+
+  const int path_flag = INTEGRATOR_STATE(path, flag);
+
+  if (path_flag & PATH_RAY_SHADOW_CATCHER_HIT) {
+    /* Shadow catcher was already hit and the state was split. No further split is allowed. */
+    return false;
+  }
+
+  return (path_flag & PATH_RAY_TRANSPARENT_BACKGROUND) != 0;
+}
+
+/* NOTE: Leaves kernel scheduling information untouched. Use INIT semantic for one of the paths
+ * after this function. */
+ccl_device_inline bool kernel_shadow_catcher_split(INTEGRATOR_STATE_ARGS, const int object_flags)
+{
+#ifdef __SHADOW_CATCHER__
+
+  if (!kernel_shadow_catcher_is_path_split_bounce(INTEGRATOR_STATE_PASS, object_flags)) {
+    return false;
+  }
+
+  /* The split is to be done. Mark the current state as such, so that it stops contributing to the
+   * shadow catcher matte pass, but keeps contributing to the combined pass. */
+  INTEGRATOR_STATE_WRITE(path, flag) |= PATH_RAY_SHADOW_CATCHER_HIT;
+
+  /* Split new state from the current one. This new state will only track contribution of shadow
+   * catcher objects ignoring non-catcher objects. */
+  integrator_state_shadow_catcher_split(INTEGRATOR_STATE_PASS);
+
+  return true;
+#else
+  (void)object_flags;
+  return false;
+#endif
+}
+
+#ifdef __SHADOW_CATCHER__
+
+ccl_device_forceinline bool kernel_shadow_catcher_is_matte_path(INTEGRATOR_STATE_CONST_ARGS)
+{
+  return (INTEGRATOR_STATE(path, flag) & PATH_RAY_SHADOW_CATCHER_HIT) == 0;
+}
+
+ccl_device_forceinline bool kernel_shadow_catcher_is_object_pass(INTEGRATOR_STATE_CONST_ARGS)
+{
+  return INTEGRATOR_STATE(path, flag) & PATH_RAY_SHADOW_CATCHER_PASS;
+}
+
+#endif /* __SHADOW_CATCHER__ */
+
+CCL_NAMESPACE_END