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How to Modify a Simple Spline?


How to Modify a Simple Spline?

Hey all,

I'm back to Pro/E after a recess on SolidWorks and it seems that somethings changed on modifying sketched spline curves.

If you sketch a simple two-point spline curve between two line segments, you typically make the spline tangent to each line segment to produce a smooth spline curve. Then, to modify the look of the curve, you right-click the spline, pick "modify", then click the button that says modify the spline by control points. This makes the little polygon that allows you to drag around the shape of the spline while keeping tangency to the line segments on each end. Or, at least this is how it used to work.

What I'm faced with now is the inability to click the "modify control points" button if I have any tangency constraints or other dimensions on the spline curve. It the spline curve is free, the button is clickable and I can drag around the control points. Further, if I make the spline tangent, then delete my tangency constraints, the control points seem to be modifiable and keep their tangency as they should (the control points only move along lines coincident with the end line segments). But, when I exit out of the modification tab, I have to reapply my tangent constraints. Usually to set up curves for boundary surfaces it a lot of playing with the end line segment to "aim" the spline, and using the "modify" tab to influence the spline to get the shape you want.

I feel like I'm going crazy, because this is a fundamental tool in surfacing that I've used for years. Something must have changed in the past couple releases. Say, in SolidWorks, if you set up the same sketch, little arrows automatically appear on the ends of the spline curve that you can pull around to influence the shape.

Thanks for any help! I feel like I'm really close, but I'm missing something here...


Good morning Karl,

You can make a "conic" as you suggest in your second paragraph. The spline creation, with 3 or more points, is 3 buttons down from there (if you have your buttons on the right side of the screen)

Wecome back from Solidworks!

Best regards,



So, I got in contact with my VAR about this issue. It seems that in WF4, the functionality that I'm talking about works with no problems. Once you go to WF5, you can no longer drag the control polygon. They have no idea why this changed. There may be a config setting or something that changes this.

If anyone knows, let me know!

--> Karl


Yeah, you could approximate a spline with conics, but its not really what I've done in the past. Thats a good workaround, though. I'd forgotten about using conics.

One person on a different forum recomended modifying the spline first, then making it tangent to your segment "levers" at each end. However, if you have to fine tune it more, then you have to delete your tangency in order to modify the spline again, then replace them again. PITA.

Another person on the same forum said my usual method worked for them and they have WF5. Somethings up...

There is a way...must use The Force...

Double Update:

I guess its a knows bug that spreads between early WF5 and Creo Versions

My vendor's response:

"It looks like PTC knows about the issue we went over this morning. It also appears there is no solution yet for Creo but it looks like if you get WF 5.0 build code m110 you should get that functionality back. See attached picture. I know this probably is not the answer you are looking for but at least you are not crazy right. I also checked to see what build code of WF 5.0 is out and it appears M120 is out so if you get WF 5.0 M120 you should be good to go. Let me know if you have any other questions."

I'm shocked that a bug like this would spread out over two full releases. If I had to make modifications to a surface model that I created in WF4, I'd be screwed. This is like not being able to change the dimensions of a circle once you tied down it's center point. So, now I have do download the latest WF5 release, do my work, then make another copy of my work in Creo so that I can send it to my client. I used to think that the one thing I liked better in Pro over SolidWorks was surfacing. Without this functionality, surfacing is almost unuseable.

Let's get it together, PTC.

This, and many other issues, is why I'm staying on WF4 until I absolutely HAVE to switch. Every time I use Creo, I get a massive headache.

hi Karl,

I think this is only possible inside style feature now.

Have you got ISDX? (interactive surface design extension) At least thats how they call it in Creo 1.0 these days.

Apparently fixed in Creo 2.0. Can edit control polys for free, 1-tangent, and 2-tangent.

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