Box2D tank - rendering over faked conveyor belts

Here is the Box2D tank using fake conveyor belts, dressed up with some even more fake textures to make it look like the track is moving.
The same surface tangent speed given to the track fixtures is used to move textures around a series of spline points and turn the wheel textures at the right speed. The points along the bottom are attached to the track segment bodies, and the points along the top are attached to a 'swing bridge' type chain which is has nothing to do with movement of the tank and is only there to calculate the points for rendering. The wheels are also only for show.
Source code and demo available here: