4

I have a line segment defined as its starting and ending points.

L = [(x1, y1), (x2, y2)]

So

               (x1, y1)                       (x2, y2)
L:                A-------------------------------B

I now wish to extend the line by pulling apart these two points like so

              a                                         a
L:      A'--------A-------------------------------B-----------B'

So I need to update the coordinates of point A and B.

Suppose A'A = B'B = a

How to do it in Python?

This question may be quite related, but mine mainly focuses on the algorithm that does the task, instead of visualizing it in the figure.

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Sibbs Gambling
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    You do it in python just like in any other language - by computing the translation and adding to the coordinates, this is not even close to the programming issue – lejlot Oct 12 '13 at 17:00
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    I think this is a math problem rather than a python problem. – Leon Young Oct 12 '13 at 17:02

1 Answers1

3

Using vector math:

B = A + v
where
   v = B - A = (x2-x1, y2-y1)
   ||v|| = sqrt((x2-x1)^2 + (y2-y1)^2)

The normalized vector v^ with ||v^|| = 1 is: v^ = v / ||v||

To get the values of A' and B' you can now use the direction
of v^ and the length of a:
   B' = B + a * v^
   A' = A - a * v^
poke
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