code: public void addBody(final GVRRigidBody gvrBody) {
          mPhysicsContext.runOnPhysicsThread(new Runnable() {
              @Override
              public void run() {
                  if (contains(gvrBody)) {
                      return;
                  }
  
                  if (gvrBody.getCollisionGroup() < 0 || gvrBody.getCollisionGroup() > 15
                          || mCollisionMatrix == null) {
                      NativePhysics3DWorld.addRigidBody(getNative(), gvrBody.getNative());
                  } else {
                      NativePhysics3DWorld.addRigidBodyWithMask(getNative(), gvrBody.getNative(),
                              mCollisionMatrix.getCollisionFilterGroup(gvrBody.getCollisionGroup()),
                              mCollisionMatrix.getCollisionFilterMask(gvrBody.getCollisionGroup()));
                  }
  
                  mPhysicsObject.put(gvrBody.getNative(), gvrBody);
                  getGVRContext().getEventManager().sendEvent(GVRWorld.this, IPhysicsEvents.class, "onAddRigidBody", GVRWorld.this, gvrBody);
              }
          });
      }
docs: Add a {@link GVRRigidBody} to this physics world.
  
  @param gvrBody The {@link GVRRigidBody} to add.