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Can the "tangent" constraint be fixed, please?

Discussion in 'General Discussion' started by JST, Apr 29, 2020.

  1. JST

    JST Alibre Super User

    Most of the constraints in Alibre constrain in a manner limited to the specific constraint dimension. If the end of a rod is constraint to align with the X-Y plane, or a planar surface of a part, it can move any where within that plane. Or if a rod is aligned with an axis, it can freely move anywhere on that axis.

    The "Tangent" constraint is unique in that it seems to constrain in multiple dimensions. This is a problem.

    For instance, I have some client work, and I needed to constrain a piece of structural pipe to lay against a piece of 5 x 5 x 3/8" angle. So of course I used tangent (I suppose I could have used align, with an offset).

    When I completed the tangent command, the piece of pipe was aligned tangent, bit was ALSO constrained, somehow, so that it could only move axially. It was not possible to move it closer to the final location. I expect that it would still respond to actual further constraints, but it could not be dragged. (In this case, I only needed it to look OK for an illustration, so I did not want to go through the hassle of establishing more planes to locate the thing.)

    I find this behavior of the tangent constraint to be anomalous, as well as extremely annoying. It create problems in workflow, since tangent must not be applied until last.

    The most irritating thing is that not every part behaves like that. Some are fine. But, cylindrical parts are particularly subject to it.

    I wonder if it is possible to fix it so that it behaves the same as the bulk of (if not all) other constraints, in limiting ONLY to its actual constraining action. The goal is to allow a tangent constrained part to be moved around "manually" in any way possible without violating the tangent constraint itself (or that combined with any other concurrent constraint).

    Is that possible? If so, can this be put on the list for an upcoming service pack or release? If not, why not?
  2. NateLiqGrav

    NateLiqGrav Alibre Super User

    Did you try turning off minimum motion mode and moving the pipe? Perhaps Alibre Design interpreted your mouse movements into rotation of the pipe instead of translation of it?
  3. JST

    JST Alibre Super User

    Possible. Last I checked MM WAS off..... got bit by that a while back.

    I'll try to remember to check that. Busy now.

    Thing is, I do not ever recall needing to fiddle with that in the past. I have not had to do the exact type of alignment for a version or two. Seems like the last couple versions have really gotten very fussy.
    Last edited: Apr 29, 2020
  4. JST

    JST Alibre Super User

    OK, checked that.

    MM is OFF.

    SOME cases will move freely, , but for some reason, others will not, even when there is only the tangent and an "orient" (offset---free) active on the part. I have no good idea what is different about the ones that do not.

    Case examined was getting some pipes mated up to flat plates.
  5. JST

    JST Alibre Super User

    I have discovered that the minimum motion mode is the default, it is ALWAYS reset to ON each time you open a model.

    AND, there seems to be no way to turn it to default of "OFF". (So you will be "bitten by it every tie unless you remember to turn it off each and every time you open a model.....:eek::rolleyes:

    PLUS, the help has exactly one entry for it, and that is terrifically non-helpful.
  6. Drutort

    Drutort Senior Member

    ya, I had strange results where it would flip and not work as it was originally defined, and this was in v21 going and reopening at a different date the asm... seems that after redoing the constraint, it had to do with the flip tag in the constraint editor. But that was strange.

    sad that MM is always on by default, this should be a setting, and should be saved in each parent file IMO

    talking about a different constraint, the angle one caused some strange behaviors when I was trying to define a - degree and on other end a 90 or so, it would flip and do strange things, so I had to cheat with an angled plane, then reference that constraint from that plane in a more traditional style of 0-89 or something along those lines

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