This simple little tool was originally designed to be used in conjunction with other PixelPlan software, as it was capable of loading and displaying PixelPlan O4C signed models and virtual 3D walks. Anyway, it can now be used as a viewer that opens and displays various types of 3D object files, including 3DS, DAE (Collada), MDL, OBJ, B3D, DXF with textures, VRML, and WRL. Furthermore, this neat 3D object file viewer can even load 3D files and textures directly form a ZIP archive, allowing you to preview 3D object files that are inside ZIP archives. That's rather convenient.
Pixelplan O4C Viewer is very simple and straightforward. But except for zooming and moving the loaded object around, it doesn't offer you much. On the other hand, though advanced users might miss some functions, the simplicity makes this tool suitable for beginners. Anyway, it's capable of providing dynamic lighting with bum-mapping and shadowing, so the quality of the displayed objects should be top class.
Since Pixelplan O4C Viewer is also free, it gets my vote of confidence and my recommendation. It's a fast and convenient solution for viewing 3D object files.