Results 3 comments of dev-zuo

@goldenratio @jnsmalm I needed this feature too, so I made a pull request for it here: https://github.com/jnsmalm/pixi3d/pull/163

@jnsmalm Sure thing! Should be fixed here: https://github.com/jnsmalm/pixi3d/pull/168

@jnsmalm Cleaned up PR here https://github.com/jnsmalm/pixi3d/pull/170