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

3 files changed, 82 insertions, 2 deletions

diff --git a/source/blender/draw/intern/DRW_render.h b/source/blender/draw/intern/DRW_render.h
index 660a4adaf51..fb8b8536897 100644
--- a/source/blender/draw/intern/DRW_render.h
+++ b/source/blender/draw/intern/DRW_render.h
@@ -623,6 +623,7 @@ const DRWView *DRW_view_default_get(void);
 void DRW_view_default_set(DRWView *view);
 void DRW_view_reset(void);
 void DRW_view_set_active(DRWView *view);
+const DRWView *DRW_view_get_active(void);
 
 void DRW_view_clip_planes_set(DRWView *view, float (*planes)[4], int plane_len);
 void DRW_view_camtexco_set(DRWView *view, float texco[4]);
diff --git a/source/blender/draw/intern/draw_manager.c b/source/blender/draw/intern/draw_manager.c
index 47adc0acc60..e65fdce5f2e 100644
--- a/source/blender/draw/intern/draw_manager.c
+++ b/source/blender/draw/intern/draw_manager.c
@@ -1197,6 +1197,18 @@ static void drw_engines_enable_basic(void)
   use_drw_engine(&draw_engine_basic_type);
 }
 
+static void drw_engine_enable_image_editor(void)
+{
+  if (DRW_engine_external_acquire_for_image_editor()) {
+    use_drw_engine(&draw_engine_external_type);
+  }
+  else {
+    use_drw_engine(&draw_engine_image_type);
+  }
+
+  use_drw_engine(&draw_engine_overlay_type);
+}
+
 static void drw_engines_enable_editors(void)
 {
   SpaceLink *space_data = DST.draw_ctx.space_data;
@@ -1205,8 +1217,7 @@ static void drw_engines_enable_editors(void)
   }
 
   if (space_data->spacetype == SPACE_IMAGE) {
-    use_drw_engine(&draw_engine_image_type);
-    use_drw_engine(&draw_engine_overlay_type);
+    drw_engine_enable_image_editor();
   }
   else if (space_data->spacetype == SPACE_NODE) {
     /* Only enable when drawing the space image backdrop. */
@@ -3188,3 +3199,66 @@ void DRW_draw_state_init_gtests(eGPUShaderConfig sh_cfg)
 #endif
 
 /** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Draw manager context release/activation
+ *
+ * These functions are used in cases when an OpenGL context creation is needed during the draw.
+ * This happens, for example, when an external engine needs to create its own OpenGL context from
+ * the engine initialization.
+ *
+ * Example of context creation:
+ *
+ *   const bool drw_state = DRW_opengl_context_release();
+ *   gl_context = WM_opengl_context_create();
+ *   DRW_opengl_context_activate(drw_state);
+ *
+ * Example of context destruction:
+ *
+ *   const bool drw_state = DRW_opengl_context_release();
+ *   WM_opengl_context_activate(gl_context);
+ *   WM_opengl_context_dispose(gl_context);
+ *   DRW_opengl_context_activate(drw_state);
+ *
+ *
+ * NOTE: Will only perform context modification when on main thread. This way these functions can
+ * be used in an engine without check on whether it is a draw manager which manages OpenGL context
+ * on the current thread. The downside of this is that if the engine performs OpenGL creation from
+ * a non-main thread, that thread is supposed to not have OpenGL context ever bound by Blender.
+ *
+ * \{ */
+
+bool DRW_opengl_context_release(void)
+{
+  if (!BLI_thread_is_main()) {
+    return false;
+  }
+
+  if (GPU_context_active_get() != DST.gpu_context) {
+    /* Context release is requested from the outside of the draw manager main draw loop, indicate
+     * this to the `DRW_opengl_context_activate()` so that it restores drawable of the window. */
+    return false;
+  }
+
+  GPU_context_active_set(NULL);
+  WM_opengl_context_release(DST.gl_context);
+
+  return true;
+}
+
+void DRW_opengl_context_activate(bool drw_state)
+{
+  if (!BLI_thread_is_main()) {
+    return;
+  }
+
+  if (drw_state) {
+    WM_opengl_context_activate(DST.gl_context);
+    GPU_context_active_set(DST.gpu_context);
+  }
+  else {
+    wm_window_reset_drawable();
+  }
+}
+
+/** \} */
diff --git a/source/blender/draw/intern/draw_manager_exec.c b/source/blender/draw/intern/draw_manager_exec.c
index 22356a3c57b..aa01ca7a262 100644
--- a/source/blender/draw/intern/draw_manager_exec.c
+++ b/source/blender/draw/intern/draw_manager_exec.c
@@ -367,6 +367,11 @@ void DRW_view_set_active(DRWView *view)
   DST.view_active = (view) ? view : DST.view_default;
 }
 
+const DRWView *DRW_view_get_active(void)
+{
+  return DST.view_active;
+}
+
 /* Return True if the given BoundSphere intersect the current view frustum */
 static bool draw_culling_sphere_test(const BoundSphere *frustum_bsphere,
                                      const float (*frustum_planes)[4],