How to invert BufferGeometry, and let's add it to BufferGeometryUtils?

[trusktr]

@orion_prime that looks correct. A glass ball make the world look upside down. See some images on Google:

https://www.google.com/search?q=refracting+glass+ball&tbm=isch

And this thread:

Refracting glass sphere, how to add some reflection

PS: I found the answer: It has to be implemented in GLSL. Thus too complex for me.