poselets body part detectors trained using 3d human pose
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Poselets: Body Part Detectors Trained Using 3D Human Pose Annotations Lubomir Bourdev and Jitendra Malik Experiments Presented by Randall Smith Friday, November 2, 12 1 Outline Introduction Dataset Overview Annotations


  1. Poselets: Body Part Detectors Trained Using 3D Human Pose Annotations Lubomir Bourdev and Jitendra Malik Experiments Presented by Randall Smith Friday, November 2, 12 1

  2. Outline • Introduction • Dataset • Overview • Annotations • Distance Function • Segmentation • Experiments • Conclusion Friday, November 2, 12 2

  3. Dataset • Humans in 3D (H3D) • 2480 annotations • (1500 train / 500 test / 240 validate) • Java3D annotation tool Friday, November 2, 12 3

  4. Dataset Friday, November 2, 12 4

  5. Overview : Training Random Seed Select Nearby Train SVMs Prune Patches Patches Residual Error Friday, November 2, 12 5

  6. Overview : Detection Run All Mean Shift Compute Max Margin Poselets Cluster Activations Hough Friday, November 2, 12 6

  7. Annotations • Bounding box placed over annotated figure Friday, November 2, 12 7

  8. Annotations • Live Demo Friday, November 2, 12 8

  9. Annotations • Live Demo Friday, November 2, 12 9

  10. Annotations : Skeleton • Annotated skeleton Friday, November 2, 12 10

  11. Annotations : Keypoints • 20 manually annotated keypoints • 15 manually annotated segments Friday, November 2, 12 11

  12. Annotations : Query Mean Examples Distance 0 0 0 0.0001 0.0001 0.0002 0.0002 0.0003 0.0005 0.0005 • Query at green box Friday, November 2, 12 12

  13. Annotations : Query Mean Examples Distance 0 0.0017 0.0020 0.0020 0.0028 0.0031 0.0032 0.0035 0.0041 0.0043 Friday, November 2, 12 13

  14. Annotations : Query Mean Examples Distance 0 0.0019 0.0079 0.0093 0.0096 0.0104 0.0134 0.0139 0.0154 0.0169 Friday, November 2, 12 14

  15. Annotations : Query Mean Examples Distance 0 0.0067 0.0086 0.0167 0.0176 0.0178 0.0180 0.0183 0.0186 0.0198 Friday, November 2, 12 15

  16. Distance Function • Paper: computes a weighted sum of Euclidean distances with additive penalty. • Implementation: Procrustes distance plus penalty. • What is the Procrustes distance? Friday, November 2, 12 16

  17. Distance Function D proc ( x 1 , x 2 ) = min s,R,t k x 1 � ( sRx 2 + t ) k • Scale so that RMS is 1.0, translate to origin, and solve for rotation matrix R. • Non visible key points ignored Friday, November 2, 12 17

  18. Distance Function D ( x s , x r ) = D proc ( x s , s r ) + Penalty • Need to compute linear least squares / SVD to solve. • Is this very expensive? Friday, November 2, 12 18

  19. Distance Function • Live Demo: 2D Toy Example Friday, November 2, 12 19

  20. Segments : UpperClothes Friday, November 2, 12 20

  21. Segments : LowerClothes Friday, November 2, 12 21

  22. Segments : Faces Friday, November 2, 12 22

  23. Detection • A simple, occlusion free test Friday, November 2, 12 23

  24. Detection Task Time Features 0.69s Detect Poselets 0.56s Score 0.82s Cluster 0.61s Localize 0.11s Total 2.49s Friday, November 2, 12 24

  25. Detection : Example • Score: 14.10. How did the clusters vote? Friday, November 2, 12 25

  26. Detection : Votes • Inspect top hits • Inspect bottom hits Friday, November 2, 12 26

  27. Detection : Best Votes Friday, November 2, 12 27

  28. Detection : Best Votes Friday, November 2, 12 28

  29. Detection : Best Votes Friday, November 2, 12 29

  30. Detection : Best Votes Friday, November 2, 12 30

  31. Detection : Worst Votes Friday, November 2, 12 31

  32. Detection : Worst Votes Friday, November 2, 12 32

  33. Detection : Worst Votes Friday, November 2, 12 33

  34. Detection : Worst Votes Friday, November 2, 12 34

  35. Detection : Tests • Some samples from PASCAL VOC2007 • With varying degrees of occlusion • Comparison with Discriminatively Trained Deformable Part Models (DPM) • Some pictures taken from my iPhone 4S • Increasingly difficult in terms of occlusion Friday, November 2, 12 35

  36. Detection : Tests • PASCAL VOC2007 Friday, November 2, 12 36

  37. Detection : Tests • Some more difficult occlusion cases Friday, November 2, 12 37

  38. Detection : Comparison • Scores: 11.50 and 2.03. • DPM failed. Friday, November 2, 12 38

  39. Detection : Comparison • Score: 5.21. 31 poselet clusters contributed. • DPM HOG parts and bounding box shown. Friday, November 2, 12 39

  40. Detection : Comparison • Scores 12.48, 9.67, and 5.40. • DPM failed. Friday, November 2, 12 40

  41. Detection : Comparison • Score 12.01. • HOG parts and bounding box shown. Friday, November 2, 12 41

  42. Detection : Comparison • Score: 5.21. • HOG parts and bounding box shown. Friday, November 2, 12 42

  43. Detection : Comparison • Both fail. Friday, November 2, 12 43

  44. Detection : Comparison • When both succeed, DPM seems to get better bounding boxes. • The poselet algorithm always tries to get the best bounding box it can. • DPM has no way of degrading gracefully. Friday, November 2, 12 44

  45. Detection : Occlusion • Score: 22.4. 54 poselet clusters contributed. Friday, November 2, 12 45

  46. Detection : Occlusion • Score: 0.29. 3 poselet clusters contributed. Friday, November 2, 12 46

  47. Detection : Occlusion • Score: 0.38. 2 poselet clusters contributed. Friday, November 2, 12 47

  48. Detection : Occlusion • Score: 0.27. 1 poselet cluster contributed. Friday, November 2, 12 48

  49. Detection : Occlusion • Score: 0.21. 2 poselet clusters contributed. Friday, November 2, 12 49

  50. Detection : Occlusion • DPM fails on all of these. • Poselets do pretty poorly, but it still computes a bounding box. • Poselets have the chance of getting it right. Friday, November 2, 12 50

  51. Conclusions • Poselets are intuitive to find in an image. • If a body part is exposed, a poselet might match it. • Poselet ranking and scoring can be understood in an intuitive way. • Can handle some occlusion • Will always try to compute a bounding box. Friday, November 2, 12 51

  52. Conclusions • Sometimes poselet activations can be misleading. • Sometimes, some poselets should have higher scores than others. • This is sort of like getting the right answer for the wrong reasons. • The dataset is very labor intensive. Friday, November 2, 12 52

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