We recently launched an application for our client that utilizes the same model with two UV maps to allow for the simulation of self- shadows.
The tiled version of the roof consists of heavily optimized UV coordinates that allow for the reuse of a dynamically created high res roof tile pattern. This was essential to the success of our project as users would be able to adjust the ratio of the tile colours, and pre- building this texture was not possible. The shadowed version of the roof consists of a greyscale image that is used to multiply the tiled roof model. We tried to find a solution that allows for real-time dynamic lighting, but it simply wasn't possible. One option that showed some promise was to render the shadow map into a video that simulated lighting from sunrise to sunset with the user being able to drag a slider to control the lighting. By interpolating between the frames in the video it is possible to simulate sunlight from almost any time of day by creating sample images at 30-minute to 1-hour increments. If anyone is interested I can try to assemble a demo showcasing this approach. You can see the final application here: http://frontiertiles.com/ Thank you to the Away3D team for making this possible.
