This project assumes that the disparity is only along a single direction (vertical in our case), and builds a three-dimensional similarity accumulator based on image shifts in that direction. The three-dimensional accumulator is essentially a stack of images, where each “layer” in the stack is the original image with a shifted second image subtracted from it.
Schmidt, H. Niemann, and S. Vogt, “Dense disparity maps in real-time with an application to augmented reality,” in Applications of Computer Vision, 2002. (WACV 2002). Proceedings. Sixth IEEE Workshop on, 2002, pp. 225–230.