VR: Initial Virtual Reality support - Milestone 1, Scene Inspection

NOTE: While most of the milestone 1 goals are there, a few smaller features and
improvements are still to be done.

Big picture of this milestone: Initial, OpenXR-based virtual reality support
for users and foundation for advanced use cases.
Maniphest Task: https://developer.blender.org/T71347
The tasks contains more information about this milestone.

To be clear: This is not a feature rich VR implementation, it's focused on the
initial scene inspection use case. We intentionally focused on that, further
features like controller support are part of the next milestone.

- How to use?
Instructions on how to use this are here:
https://wiki.blender.org/wiki/User:Severin/GSoC-2019/How_to_Test
These will be updated and moved to a more official place (likely the manual) soon.

Currently Windows Mixed Reality and Oculus devices are usable. Valve/HTC
headsets don't support the OpenXR standard yet and hence, do not work with this
implementation.

---------------

This is the C-side implementation of the features added for initial VR
support as per milestone 1. A "VR Scene Inspection" Add-on will be
committed separately, to expose the VR functionality in the UI. It also
adds some further features for milestone 1, namely a landmarking system
(stored view locations in the VR space)

Main additions/features:
* Support for rendering viewports to an HMD, with good performance.
* Option to sync the VR view perspective with a fully interactive,
  regular 3D View (VR-Mirror).
* Option to disable positional tracking. Keeps the current position (calculated
  based on the VR eye center pose) when enabled while a VR session is running.
* Some regular viewport settings for the VR view
* RNA/Python-API to query and set VR session state information.
* WM-XR: Layer tying Ghost-XR to the Blender specific APIs/data
* wmSurface API: drawable, non-window container (manages Ghost-OpenGL and GPU
  context)
* DNA/RNA for management of VR session settings
* `--debug-xr` and `--debug-xr-time` commandline options
* Utility batch & config file for using the Oculus runtime on Windows.
* Most VR data is runtime only. The exception is user settings which are saved
  to files (`XrSessionSettings`).
* VR support can be disabled through the `WITH_XR_OPENXR` compiler flag.

For architecture and code documentation, see
https://wiki.blender.org/wiki/Source/Interface/XR.

---------------

A few thank you's:
* A huge shoutout to Ray Molenkamp for his help during the project - it would
  have not been that successful without him!
* Sebastian Koenig and Simeon Conzendorf for testing and feedback!
* The reviewers, especially Brecht Van Lommel!
* Dalai Felinto for pushing and managing me to get this done ;)
* The OpenXR working group for providing an open standard. I think we're the
  first bigger application to adopt OpenXR. Congratulations to them and
  ourselves :)

This project started as a Google Summer of Code 2019 project - "Core Support of
Virtual Reality Headsets through OpenXR" (see
https://wiki.blender.org/wiki/User:Severin/GSoC-2019/).
Some further information, including ideas for further improvements can be found
in the final GSoC report:
https://wiki.blender.org/wiki/User:Severin/GSoC-2019/Final_Report

Differential Revisions: D6193, D7098

Reviewed by: Brecht Van Lommel, Jeroen Bakker

1 files changed, 26 insertions, 0 deletions

diff --git a/source/blender/makesrna/intern/rna_wm.c b/source/blender/makesrna/intern/rna_wm.c
index 929540f10ac..261f1fb9d3b 100644
--- a/source/blender/makesrna/intern/rna_wm.c
+++ b/source/blender/makesrna/intern/rna_wm.c
@@ -1266,6 +1266,20 @@ static void rna_wmClipboard_set(PointerRNA *UNUSED(ptr), const char *value)
   WM_clipboard_text_set((void *)value, false);
 }
 
+static PointerRNA rna_WindowManager_xr_session_state_get(PointerRNA *ptr)
+{
+  wmWindowManager *wm = ptr->data;
+  struct wmXrSessionState *state =
+#  ifdef WITH_XR_OPENXR
+      WM_xr_session_state_handle_get(&wm->xr);
+#  else
+      NULL;
+  UNUSED_VAR(wm);
+#  endif
+
+  return rna_pointer_inherit_refine(ptr, &RNA_XrSessionState, state);
+}
+
 #  ifdef WITH_PYTHON
 
 static bool rna_operator_poll_cb(bContext *C, wmOperatorType *ot)
@@ -2484,6 +2498,18 @@ static void rna_def_windowmanager(BlenderRNA *brna)
       prop, "rna_wmClipboard_get", "rna_wmClipboard_length", "rna_wmClipboard_set");
   RNA_def_property_ui_text(prop, "Text Clipboard", "");
 
+  prop = RNA_def_property(srna, "xr_session_settings", PROP_POINTER, PROP_NONE);
+  RNA_def_property_pointer_sdna(prop, NULL, "xr.session_settings");
+  RNA_def_property_flag(prop, PROP_NEVER_NULL);
+  RNA_def_property_ui_text(prop, "XR Session Settings", "");
+
+  prop = RNA_def_property(srna, "xr_session_state", PROP_POINTER, PROP_NONE);
+  RNA_def_property_struct_type(prop, "XrSessionState");
+  RNA_def_property_pointer_funcs(prop, "rna_WindowManager_xr_session_state_get", NULL, NULL, NULL);
+  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
+  RNA_def_property_ui_text(
+      prop, "XR Session State", "Runtime state information about the VR session");
+
   RNA_api_wm(srna);
 }