Solved

Calculation of the intersection of two 3D lines in space.

Posted on 2012-04-12
6
2,605 Views
Last Modified: 2012-04-24
If I have two lines in 3 dimensional space defined by:

Line 1:  (x1,y1,z1) and (x2,y2,z2)
Line 2: (x3,y3,z3) and (x4,y4,z4)

Does anyone have the source code to solve this?
I am working in C#.Net
0
Comment
Question by:cupper
  • 2
  • 2
  • 2
6 Comments
 
LVL 27

Accepted Solution

by:
d-glitch earned 500 total points
ID: 37839817
The method of solution is described here:  http://mathforum.org/library/drmath/view/63719.html
0
 

Author Comment

by:cupper
ID: 37839967
The proposed solution is for a point-vector pair. I'm looking for the equations for two lines, each defined by two points in space.

Line 1:  (x1,y1,z1) and (x2,y2,z2)
Line 2: (x3,y3,z3) and (x4,y4,z4)
0
 
LVL 27

Expert Comment

by:d-glitch
ID: 37840046
For each of your line segments, you can convert to point-vector form by using either point, and the difference between the two points as the direction vector.

       (x ,y ,z ) =  (x1,y1,z1)  =  t*( x2-x1), (y2-y1), (z2-z1))   for the first line.    t=0  gives  (x1,y1,z1)     and    t=1  gives  (x2,y2,z2)
0
IT, Stop Being Called Into Every Meeting

Highfive is so simple that setting up every meeting room takes just minutes and every employee will be able to start or join a call from any room with ease. Never be called into a meeting just to get it started again. This is how video conferencing should work!

 

Author Comment

by:cupper
ID: 37860770
Sorry for getting back to this so late.
In the example provided, the final answer is unclear to me (i.e. the (X,Y,Z) location of the intersection point).
Is the final intersection point (X,Y,Z) = (5,6,2)?

Also as an aside, I'm not getting the cross product he is getting in his example (see below)

from article
"Using Bensegueni's method, we find

  a(V1 x V2) = a(-10,-11,-13)"


I get  a(V x V2) =  a (-10, 11, -13)   (i.e. middle term positive).
0
 
LVL 18

Expert Comment

by:JoseParrot
ID: 37874532
In 2D, if two lines aren't parallel, it exists, for sure, an interception point.
In 3D there is another requirement: besides to be not parallel, the lines must be coplanar, say, they must be in a same plane.

The John Taylor's article Intersecting Lines in 3D: describes these conditions and gives some examples.

Jose
0
 
LVL 18

Expert Comment

by:JoseParrot
ID: 37878141
Assuming the lines are defined by their end points (x1, y1, z1) and (x2, y2, z2) lets use the general parametric equation:

      x = x1 + (x2 - x1)*t
      y = y1 + (y2 - y1)*t
      z = z1 + (z2 - z1)*t

if lines are
Line A --> (xa1,ya1, za1,  xa2,ya2, za2) and
Line B --> (xb1,yb1, zb1,  xb2,yb2, zb2),

first define the parametric equations

Line A
x = xa1 + (xa2 - xa1) * ta
y = ya1 + (ya2 - ya1) * ta
z = za1 + (za2 - za1) * ta

Line B
x = xb1 + (xb2 - xb1) * tb
y = yb1 + (yb2 - yb1) * tb
z = zb1 + (zb2 - zb1) * tb

To check if they are parallel,  get the vectors for each line.

Line A
(the components of the vector are the coefficients of ta):
M1 = (xa2 - xa1) * i + (ya2 - ya1) * j + (za2 - za1) * k

Line B
(do the same as for Line A, by using the coefficients of tb):
M2 = (xb2 - xb1) * i + ...

If M1 and M2 are equal or proportional, the lines are parallel, so there is no interception point.
If not, go ahead.

Now set the x and y values.
Of course, x and y must be the same in both lines equations, so,

x = xa1 + (xa2 - xa1) * ta = xb1 + (xb2 - xb1) * tb
and
y = ya1 + (ya2 - ya1) * ta = yb1 + (yb2 - yb1) * tb

By solving tha above equations, we have values for ta and tb.
Now, just apply these values in the z equations to chek is they are true.
If so, you found the interception point, if not, they don't intercept each another.

Jose
0

Featured Post

Threat Intelligence Starter Resources

Integrating threat intelligence can be challenging, and not all companies are ready. These resources can help you build awareness and prepare for defense.

Join & Write a Comment

This article is for Object-Oriented Programming (OOP) beginners. An Interface contains declarations of events, indexers, methods and/or properties. Any class which implements the Interface should provide the concrete implementation for each Inter…
It was really hard time for me to get the understanding of Delegates in C#. I went through many websites and articles but I found them very clumsy. After going through those sites, I noted down the points in a easy way so here I am sharing that unde…
This tutorial demonstrates a quick way of adding group price to multiple Magento products.
This video demonstrates how to create an example email signature rule for a department in a company using CodeTwo Exchange Rules. The signature will be inserted beneath users' latest emails in conversations and will be displayed in users' Sent Items…

746 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

12 Experts available now in Live!

Get 1:1 Help Now