12.07.2015 Views

To the Graduate Council: I am submitting herewith a dissertation ...

To the Graduate Council: I am submitting herewith a dissertation ...

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Chapter 3: A Feature Saliency Descriptor for Registration and Pose Recovery 34Table. 3.7. Variation of NSwithas <strong>the</strong> quality of <strong>the</strong> reconstruction degrades ( ϕ : correct rotation).ϕx: <strong>the</strong> number of salient points will decrease significantly0x0ϕxϕxϕ + 20x0ϕ + 40x0ϕ + 60x0N 1930 858 425 224SWe recall that in <strong>the</strong> 2D case <strong>the</strong> voting process for a point-set P is performed using astick field, which encodes unit vectors pointing from one siteXiT= ( x , y ) ∈ P toiiano<strong>the</strong>r siteXjT= ( x , y ) ∈ P where <strong>the</strong> vote is being cast. Following <strong>the</strong>jjformalism described in [Medioni00] <strong>the</strong> unit vector pointing from <strong>the</strong> first site to <strong>the</strong>second (indexed i and j)X − Xt )X − Xrepresentation using <strong>the</strong> covariance matrix of equation (3.8).ij i j ij ij T= = ( tx, tyis encoded in tensorijij 2 ij ij⎡(t ⎤x) txtyTij= ⎢ ij ij ij 2⎥(3.8)⎢⎣txty( ty) ⎥⎦1+ ( y2⎡ ( xi−xj)⎢⎢⎣( xi−xj)(yi− y( x −x)( y= i j i22( x − ) − )) ( − )2ixj iyjjyiyj− yj) ⎤⎥⎥⎦As we mentioned above <strong>the</strong> strength of <strong>the</strong> votes is made to decay exponentially withdistance. This decay is controlled by a par<strong>am</strong>eterσ , which is related to <strong>the</strong> scale of <strong>the</strong>

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