Add support for Ammo.js physics.

dist/super-hands.js

@@ -1074,6 +1074,9 @@ module.exports = {
   schema: {
     usePhysics: {
       default: 'ifavailable'
+    },
+    constraintComponentName: {
+      default: 'constraint'
     }
   },
   physicsInit: function () {
@@ -1091,7 +1094,7 @@ module.exports = {
     // initiate physics constraint if available and not already existing
     if (this.data.usePhysics !== 'never' && this.el.body && evt.detail.hand.body && !this.constraints.has(evt.detail.hand)) {
       const newConId = Math.random().toString(36).substr(2, 9);
-      this.el.setAttribute('constraint__' + newConId, {
+      this.el.setAttribute(this.data.constraintComponentName + '__' + newConId, {
         target: evt.detail.hand
       });
       this.constraints.set(evt.detail.hand, newConId);
@@ -1106,7 +1109,7 @@ module.exports = {
   physicsEnd: function (evt) {
     const constraintId = this.constraints.get(evt.detail.hand);
     if (constraintId) {
-      this.el.removeAttribute('constraint__' + constraintId);
+      this.el.removeAttribute(this.data.constraintComponentName + '__' + constraintId);
       this.constraints.delete(evt.detail.hand);
     }
   },
@@ -1245,8 +1248,11 @@ AFRAME.registerComponent('stretchable', inherit(base, {
     }
     let physicsShape;
     let offset;
-    for (let i = 0; i < el.body.shapes.length; i++) {
-      physicsShape = el.body.shapes[i];
+
+    // CANNON.js has el.body.shapes.  Ammo has collisionShapes in the shape component.
+    const shapesList = el.body.shapes ? el.body.shapes : el.components['ammo-shape'].collisionShapes;
+    for (let i = 0; i < shapesList.length; i++) {
+      physicsShape = shapesList[i];
       if (physicsShape.halfExtents) {
         physicsShape.halfExtents.scale(deltaStretch, physicsShape.halfExtents);
         physicsShape.updateConvexPolyhedronRepresentation();
@@ -1261,7 +1267,12 @@ AFRAME.registerComponent('stretchable', inherit(base, {
       offset = el.body.shapeOffsets[i];
       offset.scale(deltaStretch, offset);
     }
-    el.body.updateBoundingRadius();
+    if (el.body.updateBoundingRadius) {
+      // This only exists in CANNON, not Ammo.js
+      // I'm not aware of any requirement to call an equivalent function
+      // in Ammo.js
+      el.body.updateBoundingRadius();
+    }
   }
 }));