Usage of needle maps and shadows to overcome depth edges in depth map reconstruction

Photometric stereo is a method of recovering surface normals (needle map) from images. The surface integral of surface normals is used to reconstruct a depth map; however, the depth edges, which are discontinuous boundaries of the depth map, pose a problem for photometric stereo. When the surface of objects includes depth edges, the reconstructed depth map may contain errors. To solve this problem, we detect depth edges using shadows and compute a relative depth between two distant points using the widths of the corresponding shadows. We define an error function and reconstruct the depth map by minimizing the error function. Experimental results with synthetic and with real image data demonstrate the effectiveness of our approach.