add headElement to schema, so non-6DOF model can apply when head is not the active camera e.g. spectator view

Author: machenmusik

docs/components/tracked-controls.md

@@ -38,6 +38,7 @@ so using idPrefix for Vive / OpenVR controllers is recommended.
 | id                | Selects the controller from the Gamepad API using exact match.  |                            |
 | idPrefix          | Selects the controller from the Gamepad API using prefix match. |                            |
 | rotationOffset    | Offset to add to model rotation.                                | 0                          |
+| headElement       | Head element for arm model if needed (if not active camera).    |                            |
 | hand              | Which hand to use, if arm model is needed.  (left negates X)    | right                      |
 | eyesToElbow       | Arm model vector from eyes to elbow as user height ratio.       | {x:0.175, y:-0.3, z:-0.03} |
 | forearm           | Arm model vector for forearm as user height ratio.              | {x:0, y:0, z:-0.175}       |

src/components/tracked-controls.js

@@ -19,6 +19,7 @@ module.exports.Component = registerComponent('tracked-controls', {
     idPrefix: {type: 'string', default: ''},
     rotationOffset: {default: 0},
     // Arm model parameters, to use when not 6DOF. (pose hasPosition false, no position)
+    headElement: {type: 'selector'},
     hand: {type: 'string', default: 'right'},
     eyesToElbow: {default: {x: 0.175, y: -0.3, z: -0.03}}, // vector from eyes to elbow (divided by user height)
     forearm: {default: {x: 0, y: 0, z: -0.175}}, // vector from eyes to elbow (divided by user height)
@@ -50,6 +51,11 @@ module.exports.Component = registerComponent('tracked-controls', {
     this.updateButtons();
   },
 
+  /**
+   * Return head element to use for non-6DOF arm model.
+   */
+  getHeadElement: function () { return this.data.headElement || this.el.sceneEl.camera.el; },
+
   /**
    * Handle update to `id` or `idPrefix.
    */
@@ -82,9 +88,11 @@ module.exports.Component = registerComponent('tracked-controls', {
     var pose;
     var standingMatrix = this.standingMatrix;
     var vrDisplay = this.system.vrDisplay;
-    var cameraEl = el.sceneEl.camera.el;
     var data = this.data;
-    var userHeight = cameraEl.components.camera.data.userHeight || data.defaultUserHeight;
+    var headEl = this.getHeadElement();
+    var headObject3D = headEl.object3D;
+    var headCamera = headEl.components.camera;
+    var userHeight = (headCamera ? headCamera.data.userHeight : 0) || data.defaultUserHeight;
 
     if (!controller) { return; }
 
@@ -94,7 +102,7 @@ module.exports.Component = registerComponent('tracked-controls', {
     if (pose.orientation) {
       dolly.quaternion.fromArray(pose.orientation);
     } else {
-      dolly.quaternion.copy(cameraEl.object3D.quaternion);
+      dolly.quaternion.copy(headObject3D.quaternion);
     }
     if (pose.position) {
       dolly.position.fromArray(pose.position);
@@ -103,7 +111,7 @@ module.exports.Component = registerComponent('tracked-controls', {
       // Use controllerPosition and deltaControllerPosition to avoid creating yet more variables...
 
       // Use camera position as head position.
-      controllerPosition.copy(cameraEl.object3D.position);
+      controllerPosition.copy(headObject3D.position);
       // Set offset for degenerate "arm model" to elbow.
       deltaControllerPosition.set(
         data.eyesToElbow.x * (data.hand === 'left' ? -1 : data.hand === 'right' ? 1 : 0),
@@ -112,7 +120,7 @@ module.exports.Component = registerComponent('tracked-controls', {
       // Scale offset by user height.
       deltaControllerPosition.multiplyScalar(userHeight);
       // Apply camera Y rotation (not X or Z, so you can look down at your hand).
-      deltaControllerPosition.applyAxisAngle(cameraEl.object3D.up, cameraEl.object3D.rotation.y);
+      deltaControllerPosition.applyAxisAngle(headObject3D.up, headObject3D.rotation.y);
       // Apply rotated offset to position.
       controllerPosition.add(deltaControllerPosition);
 
@@ -124,7 +132,7 @@ module.exports.Component = registerComponent('tracked-controls', {
       if (pose.orientation) {
         controllerQuaternion.fromArray(pose.orientation);
       } else {
-        controllerQuaternion.copy(cameraEl.object3D.quaternion);
+        controllerQuaternion.copy(headObject3D.quaternion);
       }
       controllerEuler.setFromQuaternion(controllerQuaternion);
       controllerEuler.set(controllerEuler.x, controllerEuler.y, 0);