K, RT, el, inl, az are frequently used variables to represent camera matrix and I’ve already added comments in the code so I hope it won’t be a problem to understand. The code will be used elsewhere as a standard python script outside Blender environment as well, so using Blender libs wouldn’t be an option. As for numpy instead of Python math lib, that’s just a personal preference, wouldn’t make a difference to simplicity anyway, besides I don’t know how to use Python math. >.<