Detecting Object Instances Without Discriminative Features
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1 Detecting Object Instances Without Discriminative Features Edward Hsiao June 19, 2013 Thesis Committee: Martial Hebert, Chair Alexei Efros Takeo Kanade Andrew Zisserman, University of Oxford 1
2 Object Instance Detection Find this object under arbitrary viewpoint, lighting, clutter and occlusions 2
3 3
4 4
5 Robotic Manipulation 5
6 Scene Understanding 6
7 Scene Understanding Microwave Coffee maker Paper towel Faucet Refrigerator Stove Dishwasher 7
8 Visual Search 8
9 Recognition Using [SIFT, Lowe 2004] Discriminative Features model test image 9
10 [SIFT, Lowe 2004] Extract Keypoints model test image 10
11 [SIFT, Lowe 2004] Generate 1-To-1 Correspondences model test image 11
12 Enforce Geometric Constraints [SIFT, Lowe 2004] model test image 12
13 [SIFT, Lowe 2004] Recognized Object model test image 13
14 Failure of Feature Matching model test image 0 correct correspondences 14
15 Overview Lack of Discriminative Features Ambiguous Keypoint Features Feature-poor objects Occlusions 15
16 Overview Lack of Discriminative Features Ambiguous Keypoint Features Feature-poor objects Occlusions 16
17 Ambiguous Keypoint Features 17
18 Repeated Patterns 18
19 Failure of Discriminative Matching mdesc 1 mdesc 2... Image keypoint descriptor Model descriptors Geometric model 19
20 Failure of Discriminative Matching? or One-to-one matching mdesc 1 mdesc 2... Image keypoint descriptor Model descriptors Geometric model 20
21 Failure of Discriminative Matching? or One-to-one matching mdesc 1 mdesc 2... Image keypoint descriptor Model descriptors Geometric model Most approaches discard ambiguous features 21
22 Quantized Matching qdesc 1 qdesc 2... Image keypoint descriptor Quantized model descriptors Geometric model 22
23 Quantized Matching qdesc 1 Quantized matching qdesc 2... Image keypoint descriptor Quantized model descriptors Geometric model Preserve ambiguity of match until geometric verification 23
24 Detection Performance CMU Grocery Dataset 0.9 Average Precision (higher is better) images, 10 household objects 0 one-to-one matching [Collet et al. 2009] quantized matching 24
25 Failure of Feature Matching model test image 0 correct correspondences 25
26 Keypoint Comparison Success Failure 26
27 Uninformative Keypoints 27
28 Uninformative Keypoints 28
29 Uninformative Keypoints 29
30 Informative Keypoints 980 keypoints 10 keypoints Keypoints contained entirely within the object 30
31 Informative Keypoints 980 keypoints 10 keypoints Keypoints due to specularities 31
32 Feature-richness More keypoints Less keypoints 32
33 Feature-richness More keypoints Less keypoints 33
34 Feature-richness More keypoints Less keypoints 34
35 Feature-richness More keypoints Less keypoints 35
36 Feature Matching Experiment 36
37 Feature Matching Experiment 37
38 Feature Matching Experiment 38
39 Feature Matching Experiment At least 5 good correspondences between all pairs of images 39
40 Works Fails More keypoints Less keypoints 40
41 Works Fails More keypoints Less keypoints 41
42 Works Fails More keypoints Less keypoints 42
43 Feature-rich Feature-poor More keypoints Less keypoints 43
44 Feature-rich Feature-poor More keypoints Less keypoints 44
45 Overview Lack of Discriminative Features Ambiguous Keypoint Features Feature-poor objects Occlusions 45
46 46
47 Feature-poor Objects Shape Matching Template shape Input window Matched shape 47
48 Representing Feature-poor Objects Sparse Edge Points [Berg 2005], [Leordeanu 2007], [Duchenne 2009], [Hinterstoisser 2011] Lines & Contour Fragments [Ferrari 2006 & 2008], [Opelt 2006], [Srinivasan 2010] Histogram of Oriented Gradients (HOG) [Dalal and Triggs 2005], [Lai 2011] 48
49 Sparse Edge Points Local information: gradient orientation and color 49
50 Sparse Edge Points Matched Not matched 50
51 Sparse Edge Points Matched Not matched 51
52 Sparse Edge Points Matched Not matched Edge connectivity is lost 52
53 Lines & Contour Fragments 53
54 Lines & Contour Fragments Dependent on edge extraction Splines sensitive to occlusions Line fitting is brittle Difficult to parameterize 54
55 Lines & Contour Fragments Dependent on edge extraction Splines sensitive to occlusions Line fitting is brittle Difficult to parameterize 55
56 Histogram of Oriented Gradients Coarse statistics of gradient orientation and magnitude 56
57 Histogram of Oriented Gradients patch HOG patch HOG Corrupted by background clutter Ambiguous shape 57
58 Histogram of Oriented Gradients patch HOG patch HOG Corrupted by background clutter Ambiguous shape 58
59 Gradient Networks Our Approach 1. Match shape explicitly 2. Enforce connectivity without extracting edges 59
60 Gradient Networks Overview Shape template Input window 60
61 Gradient Networks Overview Shape template Input window 61
62 Gradient Networks Local Shape Potential How well does each pixel match locally? 62
63 Gradient Networks Predicted Shape Match Find long connected components which follow shape 63
64 Local Shape Potential Distance to template Local orientation Color Edge potential 64
65 Local Shape Potential Distance to template Local orientation Color Edge potential 65
66 Local Shape Potential Distance to template Local orientation Color Edge potential 66
67 Local Orientation Potential local orientation potential model test 67
68 Local Shape Potential Distance to template Local orientation Color Edge potential 68
69 Local Shape Potential Distance to template Local orientation Color Edge potential 69
70 Local Shape Potential 70
71 Gradient Networks p p Each pixel is a node in the network 71
72 Gradient Networks p Q 0 p p q p Q 1 Connect each node to neighbors in tangent direction 72
73 Gradient Networks p p Find paths in the network that match the shape well 73
74 [Bhat et al. 2010] Message Passing Local shape potential p shape similarity local shape potential message from left message from right 74
75 Message Passing Local shape potential p Initially, it is just the local shape potential 75
76 Message Passing Local shape potential p 76
77 Message Passing Local shape potential p 77
78 Message Passing Local shape potential p 78
79 Predicted Shape Match Message passing Local shape potential Predicted match 79
80 CMU Kitchen Occlusion Dataset 1600 images of 8 feature-poor objects Single and multiple viewpoints Cluttered scenes and occlusions Objects Example images 80
81 Shape Matching Results Template Input window Local shape potential Predicted match 81
82 Shape Matching Results Template Input window Local shape potential Predicted match 82
83 Shape Matching Results Template Input window Local shape potential Predicted match 83
84 Object Detection Sliding Window 84
85 Object Detection Sliding Window 85
86 Detection Performance better 86
87 False positives with shape only Object False positive window GN point-wise confidences 88
88 Interior Appearance Object False positive window GN point-wise confidences 89
89 BaRT Boundary and Region Templates 90
90 BaRT Boundary and Region Templates 91
91 Boundary Explicit shape: rline2d and GN 92
92 BaRT Boundary and Region Templates 93
93 Region Consider appearance within the object interior HOG and color 94
94 BaRT Boundary and Region Templates 95
95 BaRT Combines explicit boundary and region information 96
96 HOG Uniform Regions Uniform regions not represented well 97
97 HOG Normalization Each cell normalized with respect to magnitude of neighbors 98
98 HOG Normalization Amplifies noise if magnitude close to 0 99
99 Uniform Regions 100
100 Learning? HOG + SVM Multiple images weight = 0 HOG + exemplar SVM Single image weight = random 101
101 Learning? HOG + SVM Multiple images weight = 0 HOG + exemplar SVM Single image weight = random 102
102 Learning? HOG + SVM Multiple images weight = 0 HOG + exemplar SVM Single image weight = random 103
103 Modify HOG Normalization HOG Modified HOG Set cell to zero if normalization below threshold 104
104 Matching Uniform Regions HOG Ours Test image: HOG Ours 105
105 Matching Uniform Regions HOG Ours Test image: HOG Ours 106
106 Matching Uniform Regions HOG Ours Test image: HOG Ours More accurate confidences in uniform regions 107
107 Example Detections detection zoomed in boundary (GN) region (HOG+color) 108
108 Example Detections detection zoomed in boundary (GN) region (HOG+color) 109
109 Example Detections detection zoomed in boundary (GN) region (HOG+color) 110
110 Detection Performance 112
111 Detection Performance 113
112 Detection Performance Under Different Occlusion Levels 114
113 Detection Performance Under Different Occlusion Levels 115
114 Overview Lack of Discriminative Features Ambiguous Keypoint Features Feature-poor objects Occlusions 116
115 Occlusions 117
116 Occlusions 118
117 Occlusions happen in 3D 119
118 Occlusions happen in 3D 120
119 Occlusions happen in 3D 121
120 Occlusions happen in 3D 122
121 Occlusion Reasoning Matched Not matched Which of these hypotheses is most likely? 123
122 Occlusion Reasoning Matched Not matched Which of these hypotheses is most likely? 124
123 Occlusion Reasoning Matched Not matched Which of these hypotheses is most likely? 125
124 Occlusion Reasoning Matched Not matched Which of these hypotheses is most likely? 126
125 Occlusion Reasoning Local Coherency Fransens 06, Wang 09 Object Detection Depth Ordering Wu 05, Wang 11 Learn Occlusion Structure Gao 11, Kwak
126 Structure of Occlusions Occlusion Conditional Likelihood Probability a point is visible given the visibility labeling of all other points Binary variable that equals 1 if is visible Matched Not matched Occlusion under a given camera view point c 128
127 Occlusion Reasoning Per Environment H obj L obj W obj Estimate of object dimensions Distribution of object dimensions for a given environment 129
128 Occlusion Model 130
129 Occlusion Model Object Occluder 131
130 Occlusion Model Wˆobj Object Ĥ obj ĥ Occluder ŵ 132
131 Occlusion Model Wˆobj Object Ĥ obj ĥ Occluder ŵ 133
132 Occlusion Conditional Likelihood X i X j X j A Vj,O c A Vi,V j,o c Integral Geometry 134
133 Occlusion Conditional Likelihood X i X j X j A Vj,O c A Vi,V j,o c Area covering all positions where X j is visible and object occluded 135
134 Occlusion Conditional Likelihood X i X j X j A Vj,O c A Vi,V j,o c Area covering all positions where X j is visible and object occluded 136
135 Occlusion Conditional Likelihood X i X j X j A Vj,O c A Vi,V j,o c Area covering all positions where X j is visible and object occluded 137
136 Occlusion Conditional Likelihood X i X j X j A Vj,O c A Vi,V j,o c Area covering all positions where X j and X j are visible and object occluded 138
137 Occlusion Conditional Likelihood X j 139
138 Occlusion Conditional Likelihood Under Different Viewpoints 140
139 Occlusion Conditional Likelihood Under Different Viewpoints 141
140 Occlusion Conditional Likelihood Penalty (OCLP) X i Matched Not matched f OCLP : High penalty if unlikely to be occluded by a valid object on same support surface 142
141 Occlusion Conditional Likelihood Penalty (OCLP) X i Matched Not matched f OCLP : Low penalty if likely to be occluded by a valid object on same support surface 143
142 Occlusion Conditional Likelihood Penalty (OCLP) X i Matched Not matched f OCLP : Low penalty if likely to be occluded by a valid object on same support surface 144
143 Example Detections 145
144 Detection Performance 146
145 Detection Performance Under Different Occlusion Levels 147
146 Limitation Binary Matching Pattern Occlusion Conditional Likelihood 148
147 Limitation Binary Matching Pattern Occlusion Conditional Likelihood Misclassifications can have impact on distribution 149
148 Occlusion Efficient Subwindow Search (OESS) Probabilistic Matching Pattern Probabilistic Matching Pattern 150
149 OESS for True Positive Occlusion can be explained well 151
150 OESS for True Positive 95% explained 152
151 OESS for False Positive 153
152 OESS for False Positive Only 50% explained 154
153 OESS Scoring Matching Pattern p = p = 0 score = (1) + (1) + (-1) + (-1) = 0 155
154 OESS Scoring Matching Pattern p = 1 rewarded +1 Occluding block -1 p = 0 score = (1) + (1) + (1) + (-1) = 2 156
155 OESS Scoring Matching Pattern penalized p = p = 0 Occluding block score = (-1) + (1) + (1) + (-1) = 0 157
156 OESS Reformulate as Efficient Subwindow Search (ESS) 158
157 OESS Find best occluder object 159
158 OESS Remove all explained points 160
159 OESS Iterate 161
160 OESS Iterate 162
161 OESS Iterate 163
162 OESS Final prediction 164
163 Results detection window boundary region oboxes predicted groundtruth 165
164 Results detection window boundary region oboxes predicted groundtruth 166
165 Results detection window boundary region oboxes predicted groundtruth 167
166 Results detection window boundary region oboxes predicted groundtruth 168
167 Occlusion Prediction Performance predicted vs. groundtruth Average Intersection over Union (IoU) 169
168 Occlusion Prediction Performance vs. predicted groundtruth 170
169 Detection Performance 171
170 172
171 Summary Lack of Discriminative Features Gradient Networks Occlusion Conditional Likelihood Boundary and Region Templates Occlusion Efficient Subwindow Search Ambiguous Keypoint Features Feature-poor objects Occlusions 173
172 Main Contributions Ambiguous Keypoint Features Making specific features less discriminative 174
173 Main Contributions Representing Feature-poor Objects Gradient Networks Explicit shape matching without extracting edges Boundary and Region Templates Capture explicit boundary and region information 175
174 Main Contributions Representing Feature-poor Objects Gradient Networks Explicit shape matching without extracting edges Boundary and Region Templates Capture explicit boundary and region information 176
175 Main Contributions Representing Feature-poor Objects Gradient Networks Explicit shape matching without extracting edges Boundary and Region Templates Capture explicit boundary and region information 177
176 Main Contributions Occlusion Reasoning Occlusion Conditional Likelihood Representing occlusion structure under arbitrary viewpoint Occlusion Efficient Subwindow Search Directly search for occluding blocks to explain matching pattern 178
177 Main Contributions Occlusion Reasoning Occlusion Conditional Likelihood Representing occlusion structure under arbitrary viewpoint Occlusion Efficient Subwindow Search Directly search for occluding blocks to explain matching pattern 179
178 Main Contributions Occlusion Reasoning Occlusion Conditional Likelihood Representing occlusion structure under arbitrary viewpoint Occlusion Efficient Subwindow Search Directly search for occluding blocks to explain matching pattern 180
179 Acknowledgements Martial Hebert Alexei Efros Takeo Kanade Andrew Zisserman 181
180 182
181 183
182 Background 184
183 Augmented Reality 3D model Target environment 185
184 Augmented Reality 3D model Target environment 186
185 Instance vs. Category Recognition Instance Arbitrary viewpoint and lighting Single image per view Category Intra-class variations Many images per view 187
186 Ambiguous Viewpoint 188
187 Failure of SIFT Matching 189
188 Invariant Approaches 190
189 Future Directions Fine-grained verification Scalability 3D 191
190 Fine-grained Verification 192
191 Scalability 193
192 3D 194
193 Datasets 195
194 CMU Grocery Dataset 620 images of household objects 10 objects 25 single instance, 25 double instance 12 with ground truth pose Clutter, viewpoint, lighting, occlusion
195 CMU Kitchen Occlusion Dataset 1600 images of 8 household objects Single and multiple viewpoints Cluttered scenes and occlusions Objects Example images Hsiao and Hebert, CVPR
196 Gradient Networks 198
197 Local Shape Potential Region of influence Appearance Edge 199
198 Local Appearance Gradient Orientation Color 200
199 Potentials Unary Pairwise 201
200 Message Passing Shape Similarity 202
201 Probability Calibration Weibull fit to tail of negative distribution CDF of NOT Object Density of NOT Object Probability of Object NOT Object Object scores 203 Scheirer et al. CVPR 2012
202 Soft Shape Model 204
203 Additional Results 205
204 Color Potential 206
205 LINE2D Similarity Quantized gradient orientation of model point, p i θ i Quantized gradient orientation of the best matching image point in a local neighborhood p i Model point score LINE N 2 D = cos( θi ) i= 1 o cos( 0 ) = 1.00 o cos( 45 ) = 0.71 LINE2D (Hinterstoisser et al., PAMI 2011) 207
206 Robust LINE2D Similarity Quantized gradient orientation of model point, p i θ i Quantized gradient orientation of the best matching image point in a local neighborhood p i Model point N score rline 2 D = δ ( θi = 0) i= 1 rline2d (Hsiao and Hebert, CVPR 2012) 208
207 Message Passing Iterations 209
208 Probability Calibration 210
209 F-Measure of Shape Matching 211
210 Single View 212
211 Multiple View 213
212 Detection 1.0 FPPI 214
213 Detection 1.0 FPPI 215
214 False Positives 216
215 BaRT 217
216 Grid Optimization Un-optimized : 57 cells Optimized : 60 cells 218
217 HOG Normalization Amplifies noise in uniform region! 219
218 HOG Normalization Sensitive to shading effects! 220
219 HOG Normalization Pedestrians 221
220 Average Precision 222
221 Single View 223
222 Multiple View 224
223 False positives Match both boundary and region 225
224 BaRT False Positives Insufficient edge evidence Unlikely occlusion configuration Region information is only informative after there is a plausible hypothesis based on the boundary 226
225 Occlusion Reasoning 227
226 Occlusion Model 228
227 Occlusion Scoring Object detector Occlusion model Score of window Sliding window Occlusion hypothesis (binary) 229
228 Occlusion Conditional Likelihood 230
229 Occlusion Conditional Likelihood Approximation Approximate Analytic 231
230 Distribution of Physical Dimensions Household Objects 232
231 Occlusion Statistics 233
232 Validity of Occlusion Model 234
233 Occlusion Penalty Occlusion Prior Penalty (OPP) Occlusion Conditional Likelihood Penalty (OCLP) 235
234 Average Precision 236
235 Performance vs. Occlusion 237
236 Learning from Data 238
237 Parameter Sensitivity 239
238 OESS 240
239 Occlusion Upper Bound 241
240 OESS Algorithm 242
241 OESS vs. Brute Force 243
242 Occlusion Prediction 244
243 Object Detection Performance 245
244 Ambiguous Features 246
245 Problem Not enough correct matches Difficult to obtain matches Result of our system
246 Discriminative hierarchical matching (DHM) discriminative match Model features (Level 0) Image features discriminative match Quantized features (Level 1) aggregate Candidate correspondences discriminative match Quantized features (Level 2)
247 DHM example All features
248 DHM result Ratio test 3 correct matches (soymilk can) DHM 11 correct matches (soymilk can)
249 Simulated Affine (SA) Morel & Yu 2009
250 Baseline systems Gordon & Lowe SIFT + RANSAC Levenberg-Marquardt non-linear optimization Enhanced PnP (EPnP) Gordon & Lowe EPnP non-iterative pose estimation algorithm Collet et al. Gordon & Lowe Mean-shift spatial clustering of image features
251 Averaged precision-recall
252 Average Precision
253 Object detection results
254 Failure cases Pose ambiguity Repeated patterns Extreme lighting, occlusion, viewpoint etc
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