Really like your idea of the milk for acquiring images. Here in the US one can purchase ORGANIC diluted milk as the real thing. It's sold as 1%, 2%, or 5% fat content.
I think that if someone could build a STEREO digital camera with electronics that could calculate the difference in the different pixels from the two images and would give an output for the X, Y, and Z coordinates, that we would be in business; That is, if we could afford the camera.
Anyone care to take on the task?