handleMouseMoveRotate method
      
void
handleMouseMoveRotate(
    
    
- dynamic event
Implementation
void handleMouseMoveRotate(event) {
  rotateEnd.setValues(event.clientX, event.clientY);
  rotateDelta.sub2(rotateEnd, rotateStart).scale(scope.rotateSpeed);
  final element = scope.domElement;
  rotateLeft(2 * math.pi * rotateDelta.x / element.clientHeight); // yes, height
  rotateUp(2 * math.pi * rotateDelta.y / element.clientHeight);
  rotateStart.setFrom(rotateEnd);
  scope.update();
}