this is a general 3d models viewer using Irrlicht engine which support at least the following models:
and it can save any mesh to test.STL file for 3D printing

mouse and arrow keys to navigate the scene with the camera
Space key: to choose another model to view
W: wireframe
S: SolidFrame
V: save to test.STL

full working demo with the code in thinbasic and irrlicht dll and wrapper also i have added several models to test in different formats: