Chris Rebert wrote:
On Fri, Apr 9, 2010 at 8:04 AM, Peyman Askari <peter_peyman_...@yahoo.ca> wrote:
Hello
This is partly Python related, although it might end up being more math related.
I am using PyGTK (GUI builder for Python) and I need to find the intersection
point for two lines. It is easy to do, even if you only have the four points
describing line segments
(http://www.maths.abdn.ac.uk/~igc/tch/eg1006/notes/node23.html). However, it
requires that you solve for two equations. How can I do this in Python, either
solve equations, or calculating intersection points some other way?
Just solve the equations ahead of time by using generic ones.
Given:
y = mx + b
y = nx + c
We set them equal and solve for x:
mx + b = nx + c
mx - nx = c - b
(m-n)x = c - b
x = (c - b) / (m-n)
Actually, you don't want to do it that way, because it fails for vertical
lines, when m and n go to infinity.
See Wikipedia for the usual solution, given points on both lines:
http://en.wikipedia.org/wiki/Line-line_intersection
This is done all the time in computer graphics work.
John Nagle
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