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How to constrain an object based on the intersection of two other objects?

13 REPLIES 13
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Message 1 of 14
ltmullen
1022 Views, 13 Replies

How to constrain an object based on the intersection of two other objects?

Is it possible to constrain the location of one object based on the intersection of two other objects (for example, force the midpoint of one line to be at the intersection of two other lines?)

 

The reason I want to do this is specific to Civil 3D but I figured I might get the most attention for my post on this board and it might be more likely that someone who knows the answer would see it here.

 

Thanks in advance for any help you can give.

13 REPLIES 13
Message 2 of 14
nestly2
in reply to: ltmullen

You should be able to accomplish this with Geometric Constraints

 

 

Message 3 of 14
ltmullen
in reply to: nestly2

Care to elaborate, nestly?

 

I'm aware that I could constrain two lines such that the midpoint of one is always at the endpoint of another, but I'm talking about setting the midpoint of one at the intersection of two other lines. I read the descriptions of all of the GEOMCONSTRAINT methods and couldn't figure out how to make it work.

Message 4 of 14
dmfrazier
in reply to: ltmullen

Is the "intersection of two lines" always at the same point?  (Or will it change as the geometry changes?)

I'm guessing it changes, in which case I don't think there is a constraint that will do what you want (as you seem to have already discovered).

It would be helpful to all who might want to help you if you posted a simple DWG illustrating what you are trying to do and what you have already tried.

Message 5 of 14
ltmullen
in reply to: dmfrazier

No, it's not always the same point, otherwise I could just use snaps or coincident restraints.

 

It's OK, I think I know enough now to determine that I'll need to write something custom to do what I want...just wanted to see if I was missing something.

Message 6 of 14
dmfrazier
in reply to: ltmullen

See if this attached example DWG does what you are looking for.

I used COINCIDENT, selected midpoint of green line, then used Object option for one of the red lines, then repeated it for the other red line.

 

Edit: Sorry.  Attachment isn't cooperating.  I think you'll be able to figure it out from the description.

 

Message 7 of 14
ltmullen
in reply to: dmfrazier

I don't see an attached drawing.

Message 8 of 14
dmfrazier
in reply to: ltmullen

I'll try again, but in the meantime see if you can figure it out from my description.

Message 9 of 14
ltmullen
in reply to: dmfrazier

Sorry, I still couldn't make it work. What you're describing will "work" if the two lines are ending at a common point, but then it still won't let me do what I want to do.

Message 10 of 14
dmfrazier
in reply to: ltmullen

Hopefully this attachment will work.

The procedure is actually backward from what I wrote before:

Use COINCIDENT, use Object option to select one of the intersecting red lines, followed by midpoint of the green line, then repeat with the other intersecting red line.

Is that how you want things to behave?

Message 11 of 14
ltmullen
in reply to: dmfrazier

Thanks for continuing to try but I still don't see an attachment.

Message 12 of 14
dmfrazier
in reply to: ltmullen

Yes, very frustrating. Smiley Frustrated

I have now (re)installed Firefox and logged back on with it in the hope that the attachment function will work.

(I hope my efforts are not in vain, but I give up if this doesn't work... so, just in case, good luck.)

Message 13 of 14
ltmullen
in reply to: dmfrazier

Aha! You got it! Man, I'm surprised, I was becoming certain it wasn't possible. Thanks!

Message 14 of 14
dmfrazier
in reply to: ltmullen

Terrific! (Phew...)

You're welcome.

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