VR: Reset pose offsets when changing base pose

The offsets are applied after toggling positional tracking off, so that
the view does not jump at that moment. But when changing the base pose,
keeping that offset doesn't make sense. Especially with landmarks, which
are supposed to give precise positions/rotations to jump to. For that
part the VR Scene Inspection Add-on will need a little adjustment
though.

Also exposes an explicit function to the Python API to reset the
offsets, to be used by the Add-on.

This is mostly untested since I don't have access to an HMD currently.

1 files changed, 20 insertions, 1 deletions

diff --git a/source/blender/windowmanager/xr/intern/wm_xr_session.c b/source/blender/windowmanager/xr/intern/wm_xr_session.c
index dc228d1b18b..e9ff38c5a92 100644
--- a/source/blender/windowmanager/xr/intern/wm_xr_session.c
+++ b/source/blender/windowmanager/xr/intern/wm_xr_session.c
@@ -95,6 +95,11 @@ bool WM_xr_session_exists(const wmXrData *xr)
   return xr->runtime && xr->runtime->context && xr->runtime->session_state.is_started;
 }
 
+void WM_xr_session_base_pose_reset(wmXrData *xr)
+{
+  xr->runtime->session_state.force_reset_to_base_pose = true;
+}
+
 /**
  * Check if the session is running, according to the OpenXR definition.
  */
@@ -154,6 +159,17 @@ static void wm_xr_session_draw_data_populate(wmXrData *xr_data,
   wm_xr_session_base_pose_calc(r_draw_data->scene, settings, &r_draw_data->base_pose);
 }
 
+static bool wm_xr_session_draw_data_needs_reset_to_base_pose(const wmXrSessionState *state,
+                                                             const XrSessionSettings *settings)
+{
+  if (state->force_reset_to_base_pose) {
+    return true;
+  }
+  return ((settings->flag & XR_SESSION_USE_POSITION_TRACKING) == 0) &&
+         ((state->prev_base_pose_type != settings->base_pose_type) ||
+          (state->prev_base_pose_object != settings->base_pose_object));
+}
+
 void wm_xr_session_draw_data_update(const wmXrSessionState *state,
                                     const XrSessionSettings *settings,
                                     const GHOST_XrDrawViewInfo *draw_view,
@@ -166,7 +182,8 @@ void wm_xr_session_draw_data_update(const wmXrSessionState *state,
 
   /* Set the eye position offset, it's used to offset the base pose when changing positional
    * tracking. */
-  if (!state->is_view_data_set) {
+  if (!state->is_view_data_set ||
+      wm_xr_session_draw_data_needs_reset_to_base_pose(state, settings)) {
     /* Always use the exact base pose with no offset when starting the session. */
     copy_v3_fl(draw_data->eye_position_ofs, 0.0f);
   }
@@ -223,6 +240,8 @@ void wm_xr_session_state_update(const XrSessionSettings *settings,
 
   copy_v3_v3(state->prev_eye_position_ofs, draw_data->eye_position_ofs);
   state->prev_settings_flag = settings->flag;
+  state->prev_base_pose_type = settings->base_pose_type;
+  state->prev_base_pose_object = settings->base_pose_object;
   state->is_view_data_set = true;
 }