WSCG2008, Plzen, 04-07, Febrary 2008 Comparative Evaluation of Random Forest and Fern classifiers...
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WSCG2008, Plzen, 04-07, Febrary 2008WSCG2008, Plzen, 04-07, Febrary 2008
Comparative Evaluation of Random Forest and Fern Comparative Evaluation of Random Forest and Fern classifiers for Real-Time Feature Matchingclassifiers for Real-Time Feature Matching
I. Barandiaran1, C.Cottez1, C.Paloc1 , M.Graña2
1Departamento de Aplicaciones Biomédicas Asociación VICOMTech, San Sebastián, {ibarandiaran,ccottez,cpaloc}@vicomtech.org
2University of Basque Country Computer Science School, Pº. Manuel de Lardizabal, 1 20009, San Sebastián, Spain [email protected]
VISUAL INTERACTION AND COMMUNICATIONS TECHNOLOGIES
22
SummarySummary
1.Introduction.
2.Random Forest, FERNS
1.Mixed/Augmented Reality Application.
2.Conclusions/Questions.
33
IntroductionIntroduction
Motivation and objectives
• Motivated by the work of Vincent LePetit (CVLab).
• Real-Time Augmented Reality.
• Camera Pose Estimation.
• Markerless tracking.
• Model-based tracking.
• Tracking by detection.
• Test and compare different parameters.
• Scale.
• Size of the Training Set.
• Number of Classes.
• Training Time.
44
Augmented Reality Features:
• Mix Virtual and Real Objects..
• Real-Time.
• Portable Devices (Head Mounted Display, Tablet PC, PDA Device, Movil Phone..)
IntroductionIntroduction
55
Problems:
• Rendering.
• Real-Time(Delay).
• Registration/Pose Estimation.
IntroductionIntroduction
66
Non model-based Tracking
• No a priori knowledge of the object to be tracked.
• Updates/Propagates an estimation over time.
• Partial object occlusions.
• Tend to tracking reinitialization.
Model Based Tracking
• Some a priori knowledge is available.
• May not depend on the past.
• Frame by Frame estimation.
• Robust against partial object occlusion.
• Automatic tracking initialization.
IntroductionIntroduction
77
1. Introduction
2. Random Forest, FERNS
3. Mixed/Augmented Reality
4. Conclusions/Questions
SummarySummary
88
Random Forest, FERNSRandom Forest, FERNS
Tracking of Planar Surfaces.The Classifiers are applied for interest point (feature) matching.Matched Points are used during camera pose estimation Process.
99
Random Forest, FERNSRandom Forest, FERNS
Building the training set.
• Frontal view of the object to be detected.
• Feature Point extraction FAST (Rosten06) and YAPE (CvLab).
• Sub-images (patches) are generated for each class.
Classes to Be recognized by the Classifier
1010
Random Forest, FERNSRandom Forest, FERNS
Building the training set.
• Generate Random Affine transformations.
• Generate new examples of each Class.
…..
Random Affine transformations
Training Set (examples)Training Set (examples)
1111
Random ForestRandom Forest
Multiclassifier based on Randomized Trees.Firstly introduced in 1997 handwritten recognition (Amit, Y.,German, D.)Developed by Leo Breiman (Medical Data Analisys).Recently Applied to tracking by detection (LePetit06).
Main Features
• Fast Training Step, and execution.
• Good Precision.
• Random selection of the independent variables (features).
• Random selection of Examples.
• Easy to Implement and paralelizable.
1212
Random ForestRandom Forest
Classifier Training.
• N Binary-Trees are Grown.
• Pixel intensity tests are executed in any non-terminal node.
• Pixels can be selected at Random.
• Posterior Distributions P(Y=c |T=Tk,n) are stored in leave nodes.
1313
Random ForestRandom Forest
Example Classification.
• Every example is dropped down the trees.
• The Example traverse the tree towards the leaf nodes.
Pixels to be tested
TT11 TT22 TTnn
Random ForestRandom Forest
1414
Random ForestRandom Forest
Combine Results
• The example labeling is obtained as a combination of partial results obtained by every tree in the forest.
T
k
nkitlabelclass tcYPExample
1_ |maxarg
1515
FERNSFERNS
Introduced in 2007 (Mustafa Özuysal).Multiclassifier.Applied to 3D keypoint recognition.Successfully applied to image recognition/retrieval (Zisserman07).
Main Features
• Non hierarchical structure.
• Semi Naive-Bayes Combination Strategy.
• Random selection of the independent variables (features).
• Random selection of Examples.
• Easy to Implement and paralelizable.
1616
FERNSFERNS
Semi-Naive Bayes Combination.
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2121
otherwise
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1 2,1, ini cCfffPc |,....,maxarg 21
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ijin cCfPcCfffP1
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1717
FERNSFERNS
Classifier Training
x x x
32 Possible Outputs
0 7
.
.
.
ik cCFP |Posterior Distributions
(Look-up Tables)
1818
FERNSFERNS
Classifier Training
1 1 0
0 0 0
0 1 06
0 0 1 1
2
3
Class 1Class 1
Class 2Class 2
Class 1Class 1
Class 2Class 2
..
..
..
..
..
..
..
..
..
..
Fern 1Fern 1
Fern 2Fern 2
Fern Fern nn
Posterior Distributions
(Look-up Tables)
..
..
..
..
1919
FERNSFERNS
Example Classification.
M
ikflabelclass cCFPExample1
_ |maxarg
2 6 1
Posterior Distributions
(Look-up Tables)
Fern 1Fern 1 Fern 2Fern 2 Fern 3Fern 3
2020
Random Forest vs FERNSRandom Forest vs FERNS
Rotation Range
• 20 Trees, 15 Depth.
• 225 Different Clases.
• 400 Images per class.
2121
Random Forest vs FERNSRandom Forest vs FERNS
Scale Range
• 20 Trees, 15 Depth.
• 225 Different Clases.
• 400 Images per class.
2222
Random Forest vs FERNSRandom Forest vs FERNS
Size of the training Set
• 20 Trees, 15 Depth.
• 225 Different Classes.
• [0.5-1.5] Scale Range.
2323
Random Forest vs FERNSRandom Forest vs FERNS
Number of different Classes.
• 20 Trees, 15 Depth.
• [0.8-1.2] Scale Range.
• 1500 Training images per class.
2424
Random Forest vs FERNSRandom Forest vs FERNS
Training time.
• 20 Trees, 15 Depth.
• 225 Different Classes.
• [0.5-1.5] Scale Range.
0
50
100
150
200
250
300
350 550 750 1000 1500 1800 2500 2800 3800
Tra
inin
go
Tim
e (s
)
2525
Pose EstimationPose Estimation
Homography Estimation
• Robust Estimation (RANSAC).
• Non-Linear Minimization (Levenberg-Marquardt).
•
2626
SummarySummary
1. Introduction.
2. Random Forest, FERNS.
3. Mixed/Augmented Reality Application.
4. Conclusions/Questions.
2727
European Project IMPROVE (Improving Display and Rendering Technology for Virtual Environments)
• Develop of new interaction metaphors.
• Develop of new Displays.
• Photo Realistic Rendering.
• Development of Markerless Tracking Techniques.
Augmented Reality ApplicationAugmented Reality Application
2828
Augmented Reality ApplicationAugmented Reality Application
Architectural ScenarioArchitectural Scenario Automotive ScenarioAutomotive Scenario
2929
Marker-Less tracking (InDoor Scenario)Marker-Less tracking (InDoor Scenario)
Feature Points TrackingFeature Points Tracking
Textured planeTextured plane
Image AugmentationImage Augmentation
Augmented Reality ApplicationAugmented Reality Application
3030
Marker-Less tracking (OutDoor Scenario)Marker-Less tracking (OutDoor Scenario)
Image AcquisitionImage Acquisition
Feature points TrackingFeature points Tracking Image AugmentationImage Augmentation
Augmented Reality ApplicationAugmented Reality Application
3131
Performance
• 20 Trees.
• Full Rotation Range and [0.8-1.2] Scale Range.
• 1000 images per Class.
• 250 Different Classes.
Augmented Reality ApplicationAugmented Reality Application
CPU Type
0
5
10
15
20
25
Intel Core2 Duo 1,6 Ghz AMD 2,1+Ghz Pentium4 1,4Ghz Intel Centrino 1Ghz
3232
SummarySummary
1. Introduction.
2. Random Forest, FERNS.
3. Mixed/Augmented Reality Application.
4. Conclusions/Questions.
3333
ConclusionsConclusions
Both Approaches are very Similar.The classifier is more sensitive to variations in scale.The classifier is robust against variations in object orientation.When the classifier converges, increase the number of trees does not improve accuracy.The node test can be selected at random.FERNS Requires more Memmory Than Random Forest.Training and classification Time is Higher in FERNS than in Random Forest.Random Forest are Faster than FERNS (without heuristics)FERNS Supports more classes than Random Forest.The Output of both classifiers must be filtered.The higher the classification accuracy, the better the performance of the tracking.
Thanks For ListeningThanks For Listening
Iñigo Barandiaran Martirena ([email protected])
Researcher, VICOMTech
Paseo Mikeletegi 57
20009 San Sebastián
Tfno: +34 943 30 92 30 Fax : +34 943 30 93 93