Bloch Sphere axis labels orientation

[stewdio]

Currently the axis labels on the Bloch Sphere explorer attempt to always face the camera (like billboarded sprites) but instead rotate in strange ways. The proper way to fix this is to raycast from the anchor in 3D space out toward the viewer and use point where that ray intersects with the viewing plane to fix a 2D label instead. Who want to help make this happen? 😉