Movable pivot setup

The title says it all. It's a movable pivot for rotating and scaling. Inspired by this video.

Setup

pickMatrix set to filter everything but translate. Using parentMatrix here but it could be anything else. (zoom)

I wanted to avoid using any pivot attributes. We're using matrix multiplication instead. This works by multiplying the pivot's translate matrix, inversed, with its worldMatirx. So basically, we're translating back the object after the rotation/scaling is applied.

You can't orient the pivot with this setup; we'll need an extra transform object in order to do that. I wanted this setup to be as simple as possible.