# ch01b - Ch1 Object Modeling Overview Point Selection...

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Ch1 – Object Modeling • Overview • Point Selection • Bounding Box Line Equation • Least Square Line Equation • Conclusions

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Overview • Assume that we have an image of a table • How can we create a mathematical model this geometric object?
Overview • One option is to calculate the the 2D line equations for the visible edges A 1 x + B 1 y + C 1 = 0 A 2 x + B 2 y + C 2 = 0 A 3 x + B 3 y + C 3 = 0 A 4 x + B 4 y + C 4 = 0

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Overview • Assume that we have calculated the (x,y) coordinates of the table top edge pixels !! X Y 12 15 13 17 15 19 16 19 . . . . . .
Point Selection • How can we decide which points belong together on the same line? • Trial and error point selection algorithm: – Take any two points at random (x 1 ,y 1 ), (x 2 ,y 2 ) – Calculate line equation Ax+By+C=0 where A=(y 1 -y 2 ), B=(x 2 -x 1 ), C=x 1 (y 2 -y 1 )+y 1 (x 1 -x 2 ) – Find all points (x i ,y i ) that are close enough to the line by checking if Ax i +By i +C < threshold – Remove these points from the list and repeat until there are no points left to consider

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Point Selection !! Select two points and calculate line equation Ax+By+C=0
Point Selection !! Set of points that are close to the first line equation

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!! Select two more
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## This note was uploaded on 12/01/2011 for the course CSCE 5013 taught by Professor Staff during the Fall '08 term at Arkansas.

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ch01b - Ch1 Object Modeling Overview Point Selection...

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