tailieunhanh - Robot Vision 2011 Part 6

Tham khảo tài liệu 'robot vision 2011 part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 192 Robot Vision where a and b are weights. Experiments have shown that q effectively discriminates points that are quite dissimilar whereas Ci j expresses more detailed differences which should have a high impact on the final cost only when tangent orientations are alike. According to this observation we weight the difference in tangent orientation Ọij higher than shape context distances Cij. Preliminary experiments show that the method is not too sensitive to the choice of these weights but a ratio of 1 to 3 yields good results . a 1 and b 3. The costs of matching all point pairs between the two silhouettes are calculated. The Hungarian method Papadimitriou Steiglitz 1998 is used to solve the square assignment problem of identifying which one-to-one mapping between the two point sets that minimizes the total cost. All point pairs are included in the cost minimization . the ordering of the points is not considered. This is because points sampled from a silhouette with holes will have a very different ordering compared to points sampled from a silhouette without holes but with similar leg configuration see row three of Fig. 5. c second and third image for an example. By finding the best one-to-one mapping between the input silhouette and each of the database silhouettes we can now identify the best match in the whole database as the database silhouette involving the lowest total cost. 7. Gait analysis The gait analysis consists of two steps. First we do classification into one of the three gait types . walking jogging or running. Next we calculate the duty-factor D based on the silhouettes from the classified gait type. This is done to maximize the likelihood of a correct duty-factor estimation. Fig. 7. illustrates the steps involved in the gait type analysis. Note that the silhouette extraction silhouette description and silhouette comparison all process a single input frame at a time whereas the gait analysis is based on a sequence of input frames. To .