Wire3D (Wii Independent Rendering Engine 3D) is an open source, object oriented, multiplatform 3D engine written in C++, supporting homebrew Wii and Windows (DirectX). It provides a framework to developers for writing platform agnostic 3D applications (including physics using the Bullet Physics library) that run on Wii and Windows out of the box.

http://wiibrew.org/wiki/Wire3D