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, 91 insertions, 8 deletions

diff --git a/source/blender/editors/space_view3d/view3d_view.c b/source/blender/editors/space_view3d/view3d_view.c
index b27bdf93389..159ea249337 100644
--- a/source/blender/editors/space_view3d/view3d_view.c
+++ b/source/blender/editors/space_view3d/view3d_view.c
@@ -36,6 +36,7 @@
 #include "BKE_action.h"
 #include "BKE_camera.h"
 #include "BKE_context.h"
+#include "BKE_idprop.h"
 #include "BKE_object.h"
 #include "BKE_global.h"
 #include "BKE_layer.h"
@@ -228,7 +229,7 @@ void ED_view3d_smooth_view_ex(
             ob_camera_old_eval, sms.src.ofs, sms.src.quat, &sms.src.dist, &sms.src.lens);
       }
       /* grid draw as floor */
-      if ((rv3d->viewlock & RV3D_LOCKED) == 0) {
+      if ((RV3D_LOCK_FLAGS(rv3d) & RV3D_LOCK_ROTATION) == 0) {
         /* use existing if exists, means multiple calls to smooth view
          * wont loose the original 'view' setting */
         rv3d->view = RV3D_VIEW_USER;
@@ -291,7 +292,7 @@ void ED_view3d_smooth_view_ex(
       ED_view3d_camera_lock_sync(depsgraph, v3d, rv3d);
     }
 
-    if (rv3d->viewlock & RV3D_BOXVIEW) {
+    if (RV3D_LOCK_FLAGS(rv3d) & RV3D_BOXVIEW) {
       view3d_boxview_copy(sa, region);
     }
 
@@ -344,7 +345,7 @@ static void view3d_smoothview_apply(bContext *C, View3D *v3d, ARegion *region, b
       ED_view3d_camera_lock_autokey(v3d, rv3d, C, true, true);
     }
 
-    if ((rv3d->viewlock & RV3D_LOCKED) == 0) {
+    if ((RV3D_LOCK_FLAGS(rv3d) & RV3D_LOCK_ROTATION) == 0) {
       rv3d->view = sms->org_view;
     }
 
@@ -384,7 +385,7 @@ static void view3d_smoothview_apply(bContext *C, View3D *v3d, ARegion *region, b
     WM_event_add_mousemove(CTX_wm_window(C));
   }
 
-  if (sync_boxview && (rv3d->viewlock & RV3D_BOXVIEW)) {
+  if (sync_boxview && (RV3D_LOCK_FLAGS(rv3d) & RV3D_BOXVIEW)) {
     view3d_boxview_copy(CTX_wm_area(C), region);
   }
 
@@ -494,7 +495,7 @@ static bool view3d_camera_to_view_poll(bContext *C)
   if (ED_view3d_context_user_region(C, &v3d, &region)) {
     RegionView3D *rv3d = region->regiondata;
     if (v3d && v3d->camera && !ID_IS_LINKED(v3d->camera)) {
-      if (rv3d && (rv3d->viewlock & RV3D_LOCKED) == 0) {
+      if (rv3d && (RV3D_LOCK_FLAGS(rv3d) & RV3D_LOCK_ANY_TRANSFORM) == 0) {
         if (rv3d->persp != RV3D_CAMOB) {
           return 1;
         }
@@ -826,7 +827,7 @@ void view3d_viewmatrix_set(Depsgraph *depsgraph,
     bool use_lock_ofs = false;
 
     /* should be moved to better initialize later on XXX */
-    if (rv3d->viewlock & RV3D_LOCKED) {
+    if (RV3D_LOCK_FLAGS(rv3d) & RV3D_LOCK_ROTATION) {
       ED_view3d_lock(rv3d);
     }
 
@@ -991,6 +992,7 @@ int view3d_opengl_select(ViewContext *vc,
                          eV3DSelectObjectFilter select_filter)
 {
   struct bThemeState theme_state;
+  const wmWindowManager *wm = CTX_wm_manager(vc->C);
   Depsgraph *depsgraph = vc->depsgraph;
   Scene *scene = vc->scene;
   View3D *v3d = vc->v3d;
@@ -1097,7 +1099,7 @@ int view3d_opengl_select(ViewContext *vc,
   /* Important we use the 'viewmat' and don't re-calculate since
    * the object & bone view locking takes 'rect' into account, see: T51629. */
   ED_view3d_draw_setup_view(
-      vc->win, depsgraph, scene, region, v3d, vc->rv3d->viewmat, NULL, &rect);
+      wm, vc->win, depsgraph, scene, region, v3d, vc->rv3d->viewmat, NULL, &rect);
 
   if (!XRAY_ACTIVE(v3d)) {
     GPU_depth_test(true);
@@ -1165,7 +1167,8 @@ int view3d_opengl_select(ViewContext *vc,
   }
 
   G.f &= ~G_FLAG_PICKSEL;
-  ED_view3d_draw_setup_view(vc->win, depsgraph, scene, region, v3d, vc->rv3d->viewmat, NULL, NULL);
+  ED_view3d_draw_setup_view(
+      wm, vc->win, depsgraph, scene, region, v3d, vc->rv3d->viewmat, NULL, NULL);
 
   if (!XRAY_ACTIVE(v3d)) {
     GPU_depth_test(false);
@@ -1684,3 +1687,83 @@ void ED_view3d_local_collections_reset(struct bContext *C, const bool reset_all)
 }
 
 /** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name XR Functionality
+ * \{ */
+
+#ifdef WITH_XR_OPENXR
+
+static void view3d_xr_mirror_begin(RegionView3D *rv3d)
+{
+  /* If there is no session yet, changes below should not be applied! */
+  BLI_assert(WM_xr_session_exists(&((wmWindowManager *)G_MAIN->wm.first)->xr));
+
+  rv3d->runtime_viewlock |= RV3D_LOCK_ANY_TRANSFORM;
+  /* Force perspective view. This isn't reset but that's not really an issue. */
+  rv3d->persp = RV3D_PERSP;
+}
+
+static void view3d_xr_mirror_end(RegionView3D *rv3d)
+{
+  rv3d->runtime_viewlock &= ~RV3D_LOCK_ANY_TRANSFORM;
+}
+
+void ED_view3d_xr_mirror_update(const ScrArea *area, const View3D *v3d, const bool enable)
+{
+  ARegion *region_rv3d;
+
+  BLI_assert(v3d->spacetype == SPACE_VIEW3D);
+
+  if (ED_view3d_area_user_region(area, v3d, &region_rv3d)) {
+    if (enable) {
+      view3d_xr_mirror_begin(region_rv3d->regiondata);
+    }
+    else {
+      view3d_xr_mirror_end(region_rv3d->regiondata);
+    }
+  }
+}
+
+void ED_view3d_xr_shading_update(wmWindowManager *wm, const View3D *v3d, const Scene *scene)
+{
+  if (v3d->runtime.flag & V3D_RUNTIME_XR_SESSION_ROOT) {
+    View3DShading *xr_shading = &wm->xr.session_settings.shading;
+
+    BLI_assert(WM_xr_session_exists(&wm->xr));
+
+    if (v3d->shading.type == OB_RENDER) {
+      if (!(BKE_scene_uses_blender_workbench(scene) || BKE_scene_uses_blender_eevee(scene))) {
+        /* Keep old shading while using Cycles or another engine, they are typically not usable in
+         * VR. */
+        return;
+      }
+    }
+
+    if (xr_shading->prop) {
+      IDP_FreeProperty(xr_shading->prop);
+      xr_shading->prop = NULL;
+    }
+
+    /* Copy shading from View3D to VR view. */
+    *xr_shading = v3d->shading;
+    if (v3d->shading.prop) {
+      xr_shading->prop = IDP_CopyProperty(xr_shading->prop);
+    }
+  }
+}
+
+bool ED_view3d_is_region_xr_mirror_active(const wmWindowManager *wm,
+                                          const View3D *v3d,
+                                          const ARegion *region)
+{
+  return (v3d->flag & V3D_XR_SESSION_MIRROR) &&
+         /* The free region (e.g. the camera region in quad-view) is always the last in the list
+            base. We don't want any other to be affected. */
+         !region->next &&  //
+         WM_xr_session_is_ready(&wm->xr);
+}
+
+#endif
+
+/** \} */