Intersecting lines and circles

[dwade]

To get the correct intersect results for line - circle, does it make a difference which direction the line is measured or constructed from? Sometimes I get off the wall results and am wondering if direction is important.

TIA
Duane

[Matthew D. Hoedeman]

If the line intersects the circle twice, it will make a difference (so I have been told) which direction the line goes. If it goes left-to-right, you get teh intersection on the right, right-to-left and you get the left intersect.

As I said, this is what I have been told. If this is not true, blame someone else! LOL

[Wes Cisco]

Yes, the vector is critical. Are you using intersection or pierce point to construct the intersect point? If you are using Pierce the order of selection is also important, first feature selected pierces second feature selected. HTH

[#2#]

If you are creating a pierce point pc-dmis determines which side of the circle based on the line direction. I haven't really figured out which way to measure to get which side of the circle etc. Mostly I just create the point and if it is on the wrong side delete it. Then I create a line that is the reverse of the measured and create the point with that line.

[Scott Appleyard]

You have to remember that a line is "infinite". PC-DMIS will create the pierce pt where the line would first intersect the circle based on the "start" of the line, moving to the "end" of the line.

[dwade]

Well the direction of the line is backwards of what I would have thought it would be but it works.

Thanks for the help guys.

Duane