trackBall method
Implementation
void trackBall(Vector2 to, [double sensitivity = 1.0]) {
final double x = (!cameraControls.orbitX)?0:-(to.x - _from.x)/100 * sensitivity;
final double y = (!cameraControls.orbitY)?0:(to.y - _from.y)/100 * sensitivity;
rotation.x += x;
rotation.y += y;
_from.x = to.x;
_from.y = to.y;
}