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, 19 insertions, 16 deletions

diff --git a/source/blender/editors/space_view3d/view3d_gizmo_navigate.c b/source/blender/editors/space_view3d/view3d_gizmo_navigate.c
index 422cba7c52e..91a2ee297ad 100644
--- a/source/blender/editors/space_view3d/view3d_gizmo_navigate.c
+++ b/source/blender/editors/space_view3d/view3d_gizmo_navigate.c
@@ -252,14 +252,14 @@ static void WIDGETGROUP_navigate_draw_prepare(const bContext *C, wmGizmoGroup *g
       (navgroup->state.rect_visible.ymax == rect_visible->ymax) &&
       (navgroup->state.rv3d.is_persp == rv3d->is_persp) &&
       (navgroup->state.rv3d.is_camera == (rv3d->persp == RV3D_CAMOB)) &&
-      (navgroup->state.rv3d.viewlock == rv3d->viewlock)) {
+      (navgroup->state.rv3d.viewlock == RV3D_LOCK_FLAGS(rv3d))) {
     return;
   }
 
   navgroup->state.rect_visible = *rect_visible;
   navgroup->state.rv3d.is_persp = rv3d->is_persp;
   navgroup->state.rv3d.is_camera = (rv3d->persp == RV3D_CAMOB);
-  navgroup->state.rv3d.viewlock = rv3d->viewlock;
+  navgroup->state.rv3d.viewlock = RV3D_LOCK_FLAGS(rv3d);
 
   const bool show_navigate = (U.uiflag & USER_SHOW_GIZMO_NAVIGATE) != 0;
   const bool show_rotate_gizmo = (U.mini_axis_type == USER_MINI_AXIS_TYPE_GIZMO);
@@ -296,7 +296,6 @@ static void WIDGETGROUP_navigate_draw_prepare(const bContext *C, wmGizmoGroup *g
     WM_gizmo_set_flag(gz, WM_GIZMO_HIDDEN, true);
   }
 
-  /* RV3D_LOCKED or Camera: only show supported buttons. */
   if (show_rotate_gizmo) {
     gz = navgroup->gz_array[GZ_INDEX_ROTATE];
     gz->matrix_basis[3][0] = co_rotate[0];
@@ -306,26 +305,30 @@ static void WIDGETGROUP_navigate_draw_prepare(const bContext *C, wmGizmoGroup *g
 
   if (show_navigate) {
     int icon_mini_slot = 0;
-    gz = navgroup->gz_array[GZ_INDEX_ZOOM];
-    gz->matrix_basis[3][0] = roundf(co[0]);
-    gz->matrix_basis[3][1] = roundf(co[1] - (icon_offset_mini * icon_mini_slot++));
-    WM_gizmo_set_flag(gz, WM_GIZMO_HIDDEN, false);
-
-    gz = navgroup->gz_array[GZ_INDEX_MOVE];
-    gz->matrix_basis[3][0] = roundf(co[0]);
-    gz->matrix_basis[3][1] = roundf(co[1] - (icon_offset_mini * icon_mini_slot++));
-    WM_gizmo_set_flag(gz, WM_GIZMO_HIDDEN, false);
+    if ((RV3D_LOCK_FLAGS(rv3d) & RV3D_LOCK_ZOOM_AND_DOLLY) == 0) {
+      gz = navgroup->gz_array[GZ_INDEX_ZOOM];
+      gz->matrix_basis[3][0] = roundf(co[0]);
+      gz->matrix_basis[3][1] = roundf(co[1] - (icon_offset_mini * icon_mini_slot++));
+      WM_gizmo_set_flag(gz, WM_GIZMO_HIDDEN, false);
+    }
 
-    if ((rv3d->viewlock & RV3D_LOCKED) == 0) {
-      gz = navgroup->gz_array[GZ_INDEX_CAMERA];
+    if ((RV3D_LOCK_FLAGS(rv3d) & RV3D_LOCK_LOCATION) == 0) {
+      gz = navgroup->gz_array[GZ_INDEX_MOVE];
       gz->matrix_basis[3][0] = roundf(co[0]);
       gz->matrix_basis[3][1] = roundf(co[1] - (icon_offset_mini * icon_mini_slot++));
       WM_gizmo_set_flag(gz, WM_GIZMO_HIDDEN, false);
+    }
+
+    if ((RV3D_LOCK_FLAGS(rv3d) & RV3D_LOCK_ROTATION) == 0) {
+      gz = navgroup->gz_array[GZ_INDEX_CAMERA];
+      gz->matrix_basis[3][0] = co[0];
+      gz->matrix_basis[3][1] = co[1] - (icon_offset_mini * icon_mini_slot++);
+      WM_gizmo_set_flag(gz, WM_GIZMO_HIDDEN, false);
 
       if (navgroup->state.rv3d.is_camera == false) {
         gz = navgroup->gz_array[rv3d->is_persp ? GZ_INDEX_PERSP : GZ_INDEX_ORTHO];
-        gz->matrix_basis[3][0] = roundf(co[0]);
-        gz->matrix_basis[3][1] = roundf(co[1] - (icon_offset_mini * icon_mini_slot++));
+        gz->matrix_basis[3][0] = co[0];
+        gz->matrix_basis[3][1] = co[1] - (icon_offset_mini * icon_mini_slot++);
         WM_gizmo_set_flag(gz, WM_GIZMO_HIDDEN, false);
       }
     }