FIX #109121: VR: Render controllers only if they are active

When turning on VR mode, if no controllers are available,
a fallback model (a sphere) is rendered in the middle of the VR area.

This change uses the OpenXR API to check if the controllers are
available, sets new properties in `GHOST_XrPose` and `wmXrController`
that store if each controller is active or not, and uses
those properties to render the controllers in the VR view only
when they are active.

NOTE: in `wmXrController`, two state properties have been included,
but only `grip_active` is currently used. `aim_active` has been
included for consistency, but it could be removed.

Pull Request: https://projects.blender.org/blender/blender/pulls/119989

intern/ghost/GHOST_Types.h

@@ -788,6 +788,7 @@ typedef void (*GHOST_XrDrawViewFn)(const struct GHOST_XrDrawViewInfo *draw_view,
 typedef const GHOST_TXrGraphicsBinding *GHOST_XrGraphicsBindingCandidates;
 
 typedef struct {
+  bool is_active;
   float position[3];
   /* Blender convention (w, x, y, z) */
   float orientation_quat[4];

intern/ghost/intern/GHOST_XrAction.cc

@@ -339,6 +339,7 @@ void GHOST_XrAction::updateState(XrSession session,
           CHECK_XR(xrGetActionStatePose(session, &state_info, &state),
                    (std::string("Failed to get state for pose action \"") + action_name + "\".")
                        .data());
+          ((GHOST_XrPose *)m_states)[subaction_idx].is_active = state.isActive;
           if (state.isActive) {
             XrSpace pose_space = ((subaction != nullptr) && (subaction->space != nullptr)) ?
                                      subaction->space->getSpace() :

source/blender/windowmanager/xr/intern/wm_xr_draw.cc

@@ -259,6 +259,10 @@ static void wm_xr_controller_model_draw(const XrSessionSettings *settings,
   GPU_blend(GPU_BLEND_ALPHA);
 
   LISTBASE_FOREACH (wmXrController *, controller, &state->controllers) {
+    if (!controller->grip_active) {
+      continue;
+    }
+
     blender::gpu::Batch *model = controller->model;
     if (!model) {
       model = controller->model = wm_xr_controller_model_batch_create(xr_context,
@@ -334,9 +338,13 @@ static void wm_xr_controller_aim_draw(const XrSessionSettings *settings, wmXrSes
     GPU_depth_test(GPU_DEPTH_LESS_EQUAL);
     GPU_blend(GPU_BLEND_ALPHA);
 
-    immBegin(GPU_PRIM_LINES, uint(BLI_listbase_count(&state->controllers)) * 2);
-
     LISTBASE_FOREACH (wmXrController *, controller, &state->controllers) {
+      if (!controller->grip_active) {
+        continue;
+      }
+
+      immBegin(GPU_PRIM_LINES, 2);
+
       const float(*mat)[4] = controller->aim_mat;
       madd_v3_v3v3fl(ray, mat[3], mat[2], -scale);
 
@@ -344,9 +352,9 @@ static void wm_xr_controller_aim_draw(const XrSessionSettings *settings, wmXrSes
       immVertex3fv(pos, mat[3]);
       immAttr4ubv(col, color);
       immVertex3fv(pos, ray);
-    }
 
-    immEnd();
+      immEnd();
+    }
   }
   else {
     const uchar r[4] = {255, 51, 82, 255};
@@ -358,9 +366,13 @@ static void wm_xr_controller_aim_draw(const XrSessionSettings *settings, wmXrSes
     GPU_depth_test(GPU_DEPTH_NONE);
     GPU_blend(GPU_BLEND_NONE);
 
-    immBegin(GPU_PRIM_LINES, uint(BLI_listbase_count(&state->controllers)) * 6);
-
     LISTBASE_FOREACH (wmXrController *, controller, &state->controllers) {
+      if (!controller->grip_active) {
+        continue;
+      }
+
+      immBegin(GPU_PRIM_LINES, 6);
+
       const float(*mat)[4] = controller->aim_mat;
       madd_v3_v3v3fl(x_axis, mat[3], mat[0], scale);
       madd_v3_v3v3fl(y_axis, mat[3], mat[1], scale);
@@ -380,9 +392,9 @@ static void wm_xr_controller_aim_draw(const XrSessionSettings *settings, wmXrSes
       immVertex3fv(pos, mat[3]);
       immAttr4ubv(col, b);
       immVertex3fv(pos, z_axis);
-    }
 
-    immEnd();
+      immEnd();
+    }
   }
 
   immUnbindProgram();

source/blender/windowmanager/xr/intern/wm_xr_intern.hh

@@ -128,10 +128,12 @@ struct wmXrController {
   char subaction_path[64]; /* #XR_MAX_USER_PATH_LENGTH. */
 
   /** Pose (in world space) that represents the user's hand when holding the controller. */
+  bool grip_active;
   GHOST_XrPose grip_pose;
   float grip_mat[4][4];
   float grip_mat_base[4][4];
   /** Pose (in world space) that represents the controller's aiming source. */
+  bool aim_active;
   GHOST_XrPose aim_pose;
   float aim_mat[4][4];
   float aim_mat_base[4][4];

source/blender/windowmanager/xr/intern/wm_xr_session.cc

@@ -639,6 +639,7 @@ static void wm_xr_session_controller_data_update(const XrSessionSettings *settin
   wm_xr_pose_scale_to_mat(&state->nav_pose, state->nav_scale, nav_mat);
 
   LISTBASE_FOREACH_INDEX (wmXrController *, controller, &state->controllers, subaction_idx) {
+    controller->grip_active = ((GHOST_XrPose *)grip_action->states)[subaction_idx].is_active;
     wm_xr_session_controller_pose_calc(&((GHOST_XrPose *)grip_action->states)[subaction_idx],
                                        view_ofs,
                                        base_mat,
@@ -646,6 +647,7 @@ static void wm_xr_session_controller_data_update(const XrSessionSettings *settin
                                        &controller->grip_pose,
                                        controller->grip_mat,
                                        controller->grip_mat_base);
+    controller->aim_active = ((GHOST_XrPose *)aim_action->states)[subaction_idx].is_active;
     wm_xr_session_controller_pose_calc(&((GHOST_XrPose *)aim_action->states)[subaction_idx],
                                        view_ofs,
                                        base_mat,