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Does anyone use the Sketch Spline Tool?

todd_broustodd_brous Member Posts: 5
edited March 2019 in Community Support
Does anyone out there use the Sketch Spline Tool?  Basically, I think it is an unusable tool.  Its behavior appears unpredictable and genuinely unproductive.  Am I missing something?

For example, if one were to adjust a section of a curve, it will affect other areas.  This makes no sense to me.  (I think it may be time for Onshape to consider rebuilding the Spline Tool.)

Please note, that I was provided a workaround by Onshape tech support (6 months ago).  In a nutshell, rather than creating a "single spline", create multiple separate splines, and then add "tangent constraints" between the splines.  After considerable work, this can help build a desired curve shape, but this is really not a productive solution.  This is a workaround.

Also, if one needs to make any adjustments (creative or otherwise) one may find themselves wading through puddles of constraints that need to be managed/deleted/replaced.

Can we please have Adobe Illustrator-type Spline tools?

Best Answers


  • philip_thomasphilip_thomas Member, Moderator, Onshape Employees, Developers Posts: 1,381
    Todd - as a Pro user, you can submit enhancement requests like this directly to Onshape through the 'Contact Support' option on the help pulldown. Please add a few notes about the specific capabilities that you are looking for. Note also that we have added several new curve types over the past year and if there are specific cases you would help with, either tech support can help you, or a public link here will get you multiple solutions from the community at large.
    Have fun! :)
    Philip Thomas - Onshape
  • todd_broustodd_brous Member Posts: 5
    Thanks, Philip!
  • billy2billy2 Member, OS Professional, Mentor, Developers, User Group Leader Posts: 1,943 PRO
    I believe Onshape uses a b-spline as most CAD systems do.

    It's a basic spline which is a 3rd order polynomial.

    The top is one spline segment which is what I use most of the time.

    The bottom is a mirrored spline which I use often.

    I'm interested in what more do you need/want?

  • todd_broustodd_brous Member Posts: 5

    Thank you for your reply!  

    First off, using a mirrored spline is a super brilliant idea!

    I think the problem that I am experiencing is with a longer spline curve that contains multiple points and segments.  In Onshape, moving one side of the spline affects the other side.  Does that make sense?  

    Take a look at how Adobe Illustrator deals with splines.  To me, that feels like a better behavior.

    (As an aside, Onshape's auto-constraints can sometimes get in the way while "designing" a spline curve.  If you are just working out a design shape, and you accidentally place a spline point on or near an auto-constraint location, then the whole spline behavior changes until you can find and delete that constraint.  Sometimes, I think it would be nice to have an "ignore all constraints" mode while drawing in a sketch. Then one could add any needed constraints afterwards.  I, for one, do not always have my "design intent" well defined before I start working.)  

    In the below image I compare the behavior of moving a spline point in Illustrator vs Onshape.  I drew a similar "M" curve in both applications.  First, note where Onshape places the curve above and around the Spline Points.  Second, as the middle point is moved up and down, note how Onshape changes the curve shape and handle locations.  Illustrator's curve is stable and does not move or wiggle.

    To my knowledge, the way to avoid this in Onshape is to make splines with only 2 or 3 points each.  If you need a longer curve, then one will need to join and constrain multiple curves together.  I feel like this is an inefficient method, and I think it could be improved. 

    Does any of this make sense?  Note, I am quite possibly doing everything wrong in the universe.  This is just my experience.

    Thanks again for your reply!


  • todd_broustodd_brous Member Posts: 5

    Wow!  Thank you for this insight.  This demonstrates using Onshape in ways I never considered.  That is incredibly helpful.  In short, it appears that you are building a "rig" to adjust the design of the curve.  I will need to explore how this can be applied to my projects.  Regardless, this is brilliant.

    Personally, I still think I would prefer Adobe Illustrator's behavior, but you have explained and demonstrated how Onshape's curves work.  I can hope that some day the developers will take a look at expanding the Spline functionality, but in the mean time you have helped tremendously.

    My take away: 
    • Use multiple 2-point curves and connect them together.
    • Constraints are friends and enemies. 
    • Construction Guide Lines can be used to shape the curve.



  • michael_mcclainmichael_mcclain Member Posts: 198 PRO
    @billy2 thank you for showing your workflow. There are definitely some points to take away from this discussion.

    @todd_brous Hold "shift" to ignore auto constraints in sketches.
  • todd_broustodd_brous Member Posts: 5
    @michael_mcclain OMG! omg! omg... 
    Thank you!  You have just changed my life.
  • michael_mcclainmichael_mcclain Member Posts: 198 PRO
    @todd_brous check the keyboard shortcuts menu. There's a lot of good stuff in there to help make your workflow more efficient.
  • owen_sparksowen_sparks Member, Developers Posts: 2,660 PRO
    Add in some variables / configurations / relationships that drive the construction geometry and you're controlling your part without ever editing the sketch.
    Business Systems and Configuration Controller
    HWM-Water Ltd
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