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, 18 insertions, 0 deletions

diff --git a/source/blender/blenloader/intern/versioning_280.c b/source/blender/blenloader/intern/versioning_280.c
index 87442a10d12..3535897aa66 100644
--- a/source/blender/blenloader/intern/versioning_280.c
+++ b/source/blender/blenloader/intern/versioning_280.c
@@ -30,6 +30,8 @@
 #include "BLI_string.h"
 #include "BLI_utildefines.h"
 
+#include "DNA_defaults.h"
+
 #include "DNA_anim_types.h"
 #include "DNA_object_types.h"
 #include "DNA_camera_types.h"
@@ -4845,5 +4847,21 @@ void blo_do_versions_280(FileData *fd, Library *UNUSED(lib), Main *bmain)
         }
       }
     }
+
+    if (!DNA_struct_find(fd->filesdna, "XrSessionSettings")) {
+      for (wmWindowManager *wm = bmain->wm.first; wm; wm = wm->id.next) {
+        const View3D *v3d_default = DNA_struct_default_get(View3D);
+
+        wm->xr.session_settings.shading = v3d_default->shading;
+        /* Don't rotate light with the viewer by default, make it fixed. */
+        wm->xr.session_settings.shading.flag |= V3D_SHADING_WORLD_ORIENTATION;
+        wm->xr.session_settings.draw_flags = (V3D_OFSDRAW_SHOW_GRIDFLOOR |
+                                              V3D_OFSDRAW_SHOW_ANNOTATION);
+        wm->xr.session_settings.clip_start = v3d_default->clip_start;
+        wm->xr.session_settings.clip_end = v3d_default->clip_end;
+
+        wm->xr.session_settings.flag = XR_SESSION_USE_POSITION_TRACKING;
+      }
+    }
   }
 }