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Using Spline Handles

Question asked by Robert Jost

on Oct 26, 2012
Latest reply on Jul 3, 2015 by Guy Pommares

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Hi All,

Rob with SolidWorks Product Definition here. I have a question for anyone that uses spline handles.

When using the handles on spline control points, note we can pull the handle on each side separately. If you want each side to move symmetrically, you can hold down the Alt key and drag just one side.

My question is, who out there wants to weight either side of a control point separately, like this?

The reason I ask is because if you do, if affects the curvature of the spline.

I realize smooth surfaces are not the only use case for splines. So, if you typically do weight each side of a spline point separately, please let me know, and why you find this helpful.

Also, while we’re on the subject, currently it is possible to apply dimensions and constraints to spline handles in order to control various things (tangency weighting, angle etc.). Is there anything additional you wish you could do to spline handles? For example, set two to be equal, or rotate them separately?

If so, please let me know the use case as well.

Thanks everyone,

Rob

SolidWorks Product Definition

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Jerry Steiger Oct 27, 2012 1:03 PM
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Rob,

I would normally rather not manipulate the two handles separately, but sometimes it seems to be the only way to get the shape right.

Setting two handles to be equal would be nice.

I would not want to put a kink in a spline by rotating the handles separately. That seems like asking for trouble. I would use two separate splines for that case.

Jerry S.
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Neil Larsen Nov 1, 2012 12:15 AM
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ok so Richard has seen fit to remove another one of my posts because it isnt flattering.
Honestly I wish Richard wouldnt be so zealous with his censorship protective chap he is and all.
I'm trying to make a serious contribution here.
I'll try again shall I, being a little less abrupt.
I was horrified to read this is even being considered. It scares me that someone charged with the task of defining program content would ask about this.
I really dont know how someone who has a good practical understanding of the software for ID purposes would seriously propose it.
This is exactly the type of random nonsensical thing experienced users get riled and short about.
At one point someone thought it would be a good idea to rip out spline curvature comb outlines too and we saved that from improvement. Give us some credit for knowing whats needed.
Recently a Product Definition job was advertised here and I suggested rather than hire another person they should listen to early critical feedback from real world users. I'm trying to provide that here. Head it off at the pass, before it gets away on us, as it were.
If this is some intro to justify ripping out separate weighting to accomodate the inclusion of some more conics integration because the Siemens spline code is different/simpler and its convenient to cut SW down to fit the kit I would strongly oppose it.
Please put the extra effort in to doing it properly rather than taking the easy way out.
Dassault say they are committed to SW development so take some time and do it right.
Please leave the handles code as it is. Having separate weighting is very useful. Just because Product Definition types cant see the worth of it doesnt mean it should be tidied up by removing it. You want to deliberately affect the curvature like that pictured above.
I cant think of any practical use for the bent in the middle spline for sketches or surfaces constructed from them.. Like Jerry I would use 2 splines for that situation.
If you want to improve splines please fix the flipping out spline handles issue that has been in there since their introduction.
Thank you.
So Richard is that one more acceptible?
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- Jerry Steiger @ Neil Larsen on Oct 29, 2012 4:27 PM
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  Neil,
  
  I have to say that I didn't see any reason to pull your original post. It was a trifle inflammatory, but not libelous. (Well, at least not in the US.) Badly done, SolidWorks, badly done!
  
  I did almost respond to your post, but then decided that I would let Rob defend himself, or not, as he chose. I was going to say that I have seen several of the SolidWorks people post rather naive sounding questions because they don't want to presume that they already have the answers, nor to sway us in our answers. Someone posted that it is a suggested technique for soliciting input.
  
  Jerry S.
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  - Robert Jost @ Jerry Steiger on Oct 29, 2012 5:15 PM
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    Jerry, Neil,
    
    Thanks for the feedback, that’s all we are looking for. These questions are only for research, there is no intent to change any handle behavior or take anything away. We are just collecting data, and it’s very important to us that it comes directly from users. In fact, it has to. We are lucky to have a forum like this where we can easily reach out to users of all experience levels and ask a question. You both provided the answers we’re looking for, and thanks for that.
    
    Also, noted on the flipping problem being the main concern, and Neil, the suggestions you made relating to the PD position.
    
    Thanks,
    Rob
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Matt Lombard Oct 29, 2012 5:48 PM
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If someone wants a spline that isn't smooth (or even one that isn't internally c2), they should consider two splines. I avoid using interior handles because a bug in them has cost me a few thousand dollars and a good customer.

The asymmetrical interior handles are something I never really fully embraced. It's a pretty esoteric area when compared against other things that need attention, even other things within splines that need attention.

At this point, I think the less you eff with it, the better. We have workarounds for most of the bugs, and re-finding bugs, re-learning workarounds isn't attractive unless there's going to be some major trade-off.
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- Jerry Steiger @ Matt Lombard on Oct 30, 2012 2:28 PM
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  Matt,
  
  Can you remind me what the problem was with the interior handles? I am tempted to use them every once in a while. A little reminder of how I could get burned would be helpful.
  
  Jerry S.
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  - Neil Larsen @ Jerry Steiger on Oct 30, 2012 7:48 PM
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    I think Matt is talking about the issue he described in this blog post
    http://www.dezignstuff.com/blog/?p=7033
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    - Jerry Steiger @ Neil Larsen on Oct 31, 2012 5:10 PM
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      Neil,
      
      Thanks! Even if it is not the issue Matt was thinking of it was a good reminder.
      
      Jerry S.
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Guy Pommares Jul 3, 2015 11:32 PM
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Yes I very much would like the spline handles to be controlled separately.
This is necessary when modelling Coons surfaces, for example in a car hood.
Also if I could move them at distinct angles, that would allow me to make
curves with breaks in them. I do it frequently in other environments. Is
there a way to do this in SolidWorks. As per the last sketch in your post.
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Using Spline Handles

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