I’ve been looking at the positions and rotations of the individual particles. Updating position while in billboard mode seems to behave as I would initially expect. I’m assuming that the individual particle positions are in global space, since the position updates are independent of my camera position.

However, the same cannot be said for rotation. I know that there’s some coordinate transformation math needed, and this is where I wonder whether there exist constants that I can use which would do quick global/local space transform. Since rotation is entirely based on the local space of the particle, how would I go about having billboard particles rotating about the center of this scene globally?

I don’t know how I would go about performing these transformations, as the camera view vector affects how the billboards (and, thus, their local Y axis) face.