https://beyond-all-reason.github.io/spring/lua-api/types/UnsyncedCallins mentions a bunch of Draw* callins. This was fancy 15 years ago, but nowadays it's a performance antipattern due to engine - Lua - engine roundtrips for each drawable object. Some games might still use them and they work, but generally we should mark it such that it's clear we don't want people to do it like that.