XR Controller Support Step 4: Controller Drawing

Addresses T77127 (Controller Drawing).

Adds VR controller visualization and custom drawing via draw
handlers. Add-ons can draw to the XR surface (headset display) and
mirror window by adding a View3D draw handler of region type 'XR' and
draw type 'POST_VIEW'.  Controller drawing and custom overlays can be
toggled individually as XR session options, which will be added in a
future update to the VR Scene Inspection add-on.

For the actual drawing, the OpenXR XR_MSFT_controller_model extension
is used to load a glTF model provided by the XR runtime. The model's
vertex data is then used to create a GPUBatch in the XR session
state. Finally, this batch is drawn via the XR surface draw handler
mentioned above.

For runtimes that do not support the controller model extension, a
a simple fallback shape (sphere) is drawn instead.

Reviewed By: Severin, fclem

Differential Revision: https://developer.blender.org/D10948

1 files changed, 4 insertions, 1 deletions

diff --git a/source/blender/makesdna/DNA_screen_types.h b/source/blender/makesdna/DNA_screen_types.h
index f557890e3e8..86fd6b9744a 100644
--- a/source/blender/makesdna/DNA_screen_types.h
+++ b/source/blender/makesdna/DNA_screen_types.h
@@ -666,8 +666,11 @@ typedef enum eRegion_Type {
   RGN_TYPE_EXECUTE = 10,
   RGN_TYPE_FOOTER = 11,
   RGN_TYPE_TOOL_HEADER = 12,
+  /* Region type used exclusively by internal code and add-ons to register draw callbacks to the XR
+     context (surface, mirror view). Does not represent any real region. */
+  RGN_TYPE_XR = 13,
 
-#define RGN_TYPE_LEN (RGN_TYPE_TOOL_HEADER + 1)
+#define RGN_TYPE_LEN (RGN_TYPE_XR + 1)
 } eRegion_Type;
 
 /* use for function args */