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, 8 insertions, 0 deletions

diff --git a/source/blender/draw/engines/external/external_engine.h b/source/blender/draw/engines/external/external_engine.h
index c645fb99e0e..14ec4e2d3c5 100644
--- a/source/blender/draw/engines/external/external_engine.h
+++ b/source/blender/draw/engines/external/external_engine.h
@@ -22,4 +22,12 @@
 
 #pragma once
 
+extern DrawEngineType draw_engine_external_type;
 extern RenderEngineType DRW_engine_viewport_external_type;
+
+/* Check whether an external engine is to be used to draw content of an image editor.
+ * If the drawing is possible, the render engine is "acquired" so that it is not freed by the
+ * render engine for until drawing is finished.
+ *
+ * NOTE: Released by the draw engine when it is done drawing. */
+bool DRW_engine_external_acquire_for_image_editor(void);