Just thought id let you know that i have uploaded a project to ticalc.org today. It is a 3D engine for the TI-83+ series calculators.
The program is a 3D model viewer that enables the user to view and interact with a 3D model in real-time. Note that it renders flat pattern-shaded polygons. Also included is a utility to convert Wavefront OBJ models to .8xp programs for use with this viewer.
It is written in z80 assembly and a 15MHz calculator is recommended.
It is in beta testing so there could be problems. Please report any bugs if you find any.