Projected Curve in 2D? (average of two splines)

NAE

Hello,

I am trying to get an average of 2 splines on the same sketch. Ideally, it could be a single, or multiple splines between the two splines.

Single line between:



Multiple lines between:


Any ideas?

Alex_Kempen

You can average two straight (non-spline) lines by creatively using a symmetric constraint - make the two lines you want to average symmetric about another line which goes down the middle. You’ll still need to do some work constraining the ends, but it should be pretty close to what you want.

As to 2D splines, I’m not sure there’s an easy way to do so in sketches since their shape is quite custom. You also can’t use custom features in sketches, so there’s not a lot that can be done outside of the standard toolset provided by Onshape.

if you explain why you need averaged splines and/or what you’re trying to accomplish with this, myself and others might be able to provide better suggestions.

NAE

I am literally trying to accomplish lines 

This is more art than engineering, here's a recent piece:

NAE

Through a search, I found that Rhino has a tool called "TweenCurves"
http://docs.mcneel.com/rhino/5/help/en-us/commands/tweencurves.htm

I'm an engineer at heart, so my first tools are CAD tools. I think I'll jump the shark and try something like Rhino for this - not everything is a nail, as they say.

BenTaylor

I'm not sure how robust this technique is, but you could:

• create a sketch with 2 base splines.
• create another sketch on the same plane.
• draw vertical construction lines with as many segments as you want between the points of the base splines.
• constrain all collinear construction lines to be equal.
• draw a spline with a point on each of those points.

Here's an example: Spline Averaging

If you really want this functionality in OnShape, you could write a FeatureScript that allowed you to select the top and bottom curve, set the number of internal curves, and have it generate them for you. I'm not experienced in that area of OnShape yet, though.

NAE

@BenTaylor
I like it! That makes a lot of sense, I don't know FeatureScript either. 

Can anyone suggest a starting point on this?

NeilCooke

evEdgeTangentLines() will give you points along a spline, then all you have to do is simple math to get interpolated points and then use opFitSpline() - simples

steve_shubin

@NAE

Here is a workaround

Utilizing @Evan_Reese Face Curves featurescript —

1) take two splines

2) loft them

3) use the Face Curves FS to tween

4) project curves to plane with USE tool

steve_shubin

@NAE

https://cad.onshape.com/documents/856584e90d438305da9f92ae/w/c1797f57d9cd6a6b27d59a69/e/1f3e0dfb57eaf3a2fc7b7643

steve_shubin

@NAE

EvanReese

@steve_shubin
this use case is literally one of the reasons I was so excited to make that feature. Loft + Face Curves = Tween Curves. As someone who also uses Rhino, this got me excited. If all you want is lines, Adobe Illustrator can do this with the blend tool too.

steve_shubin

@Evan_Reese

You know Evan, it seems like lately, whenever I’m doing something, there’s a real good chance I’m gonna be looking for one of yours or Konstantin’s tools.

Both of you guys are making some great FeatureScripts 

Thanks for all the hard work

NAE

@Evan_Reese Nice work on the Face Curves! 
I very much appreciate you sharing your work with the world. #goodhuman

Thanks, @steve_shubin for the tutorial as well! 

EvanReese

☺️