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2D sketch tangent constraint between line and spline


Hi, I don't know what I'm doing wrong, but I can't seem to reliably get a tangent constraint between a straight line and a spline in a 2D sketch (in Atom3D). I can get it to do it about probably 1 time in 20, is there some trick other than setting the end points coincident and then selecting the two lines and hitting tangent? Note that I am a complete noob to this, as all I've done so far is load up an example file and tnen try drawing this sketch with arbitrary geometry.

I've attached a file where I've managed to create the tangent constraint. But if I delete that constraint and try to readd it (without moving anything around) then it won't add it again. Very strange (or more likely user incompetence!).



  • test - spline tangent.AD_PRT
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Alibre Super User
Splines do not seem to be quite "real" in Alibre (or other programs).

Some things may not attach to them, at least not where you prefer. They act like they are "generated anew" every time the file is opened or refreshed, and maybe they are. They do not act as if they are well-defined objects.


Senior Member
If you are a newbie, practice on other things and stay away from splines until you REALLY need to.
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Ex Machina

Hello everyone,

I have the same issue as the OP and I can't seem to find a solution to it either. Is there a way to get a spline to end tangent or perpendicular to another line?

I tried using a spline by control points and constraining them to a suitable reference line, which gets me the geometry I want but is then not parametric. Changing the location of that line by a linear or angular dimension does not bring the control point along. Only the end point of the spline.

Any help is much appreciated.


Alibre Super User
Hello Konstantinos,

one way to get a spline tangetial to a line is:
draw a line, add a spline by reference points to the line

move the reference point next from the line to spline connection point as long as the tangential contraint symbol occurs


adding dimensions to the reference point seems to be not possible...

overall splines are in Alibre are not the best tool...


Ex Machina

Oh, cool. I did figure out it had something to do with spline by control points, but I hadn't tried it like that. I made reference lines and used the coincident constraint.

Do you know if that tangent constraint will regen if the first line (on the left of your pic) moves?

P.S. By the way, if those control points were sketch entities, like nodes, for example, that would help the spline design process immensely.
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