For my 15-112 (Fundamentals of Computer Programming) final project I created a 3D STL viewer. It is a 3D renderer complete with ray teaching light reflections, as well as rotation based on the user's mouse input. Take a look at my video for information on this project.
If you would like to take a look at my code go ahead. Just please don't copy it without permission.
Here is a link. The code is written entirely in Python and only uses the built in image library TkInter. It includes a couple of STL files to view as well.