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Artificial Intelligence and Soft Computing: Behavioral ... - Arteimi.info

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I (u, v)<br />

YI<br />

Fig. 17.12: Camera model of 3-D perspective projection.<br />

The reason: why parallel rail lines at the furthest end seem to be<br />

unparallal (converging) can now be ascertained. Let us consider a point Pm on<br />

the line passing through (x, y, z) in the direction (p, q, r). The coordinate of<br />

the point then will be (x + m p, y + m q, z + m r). The perspective projection<br />

of Pm on the image plane is given by<br />

(u, v) = ( -f (x + m p) / (z+ m r), -f (y + m q) / (z +m r)). (17.14)<br />

When m approaches infinity, (u, v) approaches (- f p / r, -f q / r), then<br />

we call Pm at m →∝ to be the vanishing point. It may be noted that as m →∝,<br />

the projected image point does not depend on the point (x, y, z). Thus parallel<br />

lines are mapped at a given point (- f p / r, -f q / r) <strong>and</strong> consequently the<br />

parallel lines seem to be converging at the furthest end.<br />

17.4.2.2 Stereo Vision<br />

f<br />

Optical<br />

Center<br />

XI<br />

Yc=Y<br />

Xc=X<br />

Global <strong>and</strong> camera<br />

coordinate system<br />

(coincident)<br />

Front<br />

Projection<br />

Option<br />

P (x, y, z)<br />

3D object point<br />

Zc=Z (Optical Axis)<br />

The objective of stereo vision is to recover the geometric structure of objects in<br />

a scene from multiple images. Generally the images of a scene are taken from

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