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Message 1 of 14 (159 Views)

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

159 Views, 13 Replies
11-12-2013 06:23 AM

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.

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Message 2 of 14 (131 Views)

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

11-12-2013 09:52 PM in reply to: pocketmerlin

You should be able to accomplish this with Geometric Constraints

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Message 3 of 14 (121 Views)

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

11-13-2013 07:33 AM in reply to: nestly

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.

**Master
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Message 4 of 14 (117 Views)

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

11-13-2013 08:09 AM in reply to: pocketmerlin

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.

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Message 5 of 14 (112 Views)

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

11-13-2013 08:21 AM 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.

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Message 6 of 14 (105 Views)

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

11-13-2013 08:42 AM in reply to: pocketmerlin

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.

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Message 7 of 14 (102 Views)

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

11-13-2013 08:46 AM in reply to: dmfrazier

I don't see an attached drawing.

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Message 8 of 14 (96 Views)

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

11-13-2013 08:48 AM in reply to: pocketmerlin

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

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Message 9 of 14 (87 Views)

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

11-13-2013 08:59 AM 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.

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Message 10 of 14 (84 Views)

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

11-13-2013 09:06 AM in reply to: pocketmerlin

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?

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