How to draw a 3D circle that is tangent to two lines

Hi,

May I ask that, I have two 3D lines on the same plane, and I have two known point on the individual line. the angle between two lines is unknown. And now I want to draw a circle that is tangent to both of the lines (on the same plane), and intersect the two known points. Is there a way to do this in matlab. Really appreciated for the help.

Thank you.

[Sindar]

First, you need to know how to do it "by hand," then you can code the math up in Matlab. This (non-Matlab) question seems relevant

[MingCheng Zhang]

yap, totally agreely, I should have done that. Thank you for the help~

Answer 1

[John D'Errico]

First, if the lines are in the same plane, then you can pretend this is a problem in 2-dimensions. You can always rotate everything into the plane containing the lines. That part is easy enough. So pretend you have done so.

Now consider two lines that are NOT parallel, both of which lie in the plane. They must intersect at some point.

What is the circle that is tangent to both lines? Hint: There is no unique circle. There are INFINTELY many circles tangent to two intersecting lines. All such circles have their center along the line passing through the intersection of the lines.

So you cannot draw THE circle.

[MingCheng Zhang]

Thank you!