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Multi-View Geometry (Cont.). Stereo Constraints (Review). p’. ?. p. Given p in left image, where can the corresponding point p’ in right image be?. Epipolar Line. p’. Y 2. X 2. Z 2. O 2. Epipole. Stereo Constraints (Review). M. Image plane. Y 1. p. O 1. Z 1. X 1. Focal plane.
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Stereo Constraints (Review) p’ ? p Given p in left image, where can the corresponding point p’in right image be?
Epipolar Line p’ Y2 X2 Z2 O2 Epipole Stereo Constraints (Review) M Image plane Y1 p O1 Z1 X1 Focal plane
P p p’ O’ O From Geometry to Algebra (Review)
P p p’ O’ O From Geometry to Algebra (Review)
Linear Constraint:Should be able to express as matrix multiplication.
The Essential Matrix • Based on the Relative Geometry of the Cameras • Assumes Cameras are calibrated (i.e., intrinsic parameters are known) • Relates image of point in one camera to a second camera (points in camera coordinate system). • Is defined up to scale • 5 independent parameters
The Essential Matrix Similarly p is the epipolar line corresponding to p in theright camera
The Essential Matrix Similarly, Essential Matrix is singular with rank 2 e’
Velocity Vector Translational Component of Velocity Angular Velocity Motion Models (Review) 3D Rigid Motion
Small Motions Velocity Vector Translational Component of Velocity Angular Velocity
Translating Camera Focus of expansion (FOE): Under pure translation, the motionfield at every point in the image points toward the focus ofexpansion
Review: Intrinsic Camera Parameters Y M Image plane C Z v X Focal plane m u P
Fundamental Matrix If u and u’ are corresponding image coordinates then we have
Fundamental Matrix Fundamental Matrix is singular with rank 2 In principal F has 7 parameters up to scale and can be estimatedfrom 7 point correspondences Direct Simpler Method requires 8 correspondences
Estimating Fundamental Matrix The 8-point algorithm Each point correspondence can be expressed as a linear equation
Basic Stereo Derivations Derive expression for Z as a function of x1, x2, f and B
Basic Stereo Derivations Define the disparity: