Celestia Forums

I'm trying to create a randomised cratered texture, just wondering if there are any equations to describe how a circle appears when it is represented in the cylindrical projection used in Celestia?

Craters that are small in comparison to the planetary radius become ellipses with vertical dimension = (crater radius) and horizontal dimension = (crater radius)/cos(latitude).
Large craters become noticeably distorted from a simple ellipse, as (of course) do those that actually contain a rotation pole within their rimwall. When I played with this myself I ended up writing a routine that plotted the rims of large craters in short segments - it wasn't a huge computational overhead, since large craters are rare.

Grant