\\textbf{Left}: A sample frame of the Crossing video. Two pedestrians at left are crossing the street while the one at right is waiting. The provided bounding boxes were used instead of running the \ntracking/segmentation algorithm. \\textbf{Center}: Affinity matrix. \\textbf{Right}: Binarized affinity matrix after applying the threshold $\\tau = 0.9/2= 0.45$. Two groups are correctly detected. \n(This is a color figure.)