Points and tangents across a spline

lawrence_rosdobutko

Hey all, I'm crazy new to onshape so I might ramble a bit trying to get to the point of my question but I'll try to keep it short. From the title it might not be quite clear what it is I'd like to do, but what I want is to be able to change the degree of curvature between points on a spline. For instance, in this screenshot http://puu.sh/ipj9U/769d66092c.png the 3 point spline has nodes that you can move around to adjust the position and the radius/curve of the end points, but not the middle point. 
Further, on a closed spline such as in this screenshot http://puu.sh/ipjeM/a7641d44d9.jpg none of the 4 points has a node for adjusting the curve between each point in a parametric way.
Is there such a way to adjust the points numerically, or at least with some manner of control?
I'd love to hear from you guys who are in the know!
Thanks for your time!

andrew_troup

At present one way (possibly the only way?) to achieve this is by stringing together a contiguous, closed loop from a series of 2-point splines, setting each end of each spline tangent to the near end of the adjacent spline.

I would build an underlying criss-cross network of lines which intersected at the desired points, in a separate sketch, so you can snap the spline points to those intersections.

You can then dimension the tangency angles to the underlying lines, and finally dimension the lengths of the tangency handles to adjust the weighting.

This represents quite a lot of somewhat exacting work, and is possibly not a viable proposition unless you only have a relatively small number of profiles to build.

andrew_troup

@lawrence_rosdobutko
I don't know of a better way than the one I describe.

Onshape is in its infancy, and curvy shapes based on analytical geometry will doubtless receive considerable attention from the development team in due course, but at present I get the sense that they are trying to create a solid foundation, with emphasis on the creation of "primitive" geometry, 

_Ðave_

You could dimension the node points like in this pic. hope that helps.

andrew_troup

At present one way (possibly the only way?) to achieve this is by stringing together a contiguous, closed loop from a series of 2-point splines, setting each end of each spline tangent to the near end of the adjacent spline.

I would build an underlying criss-cross network of lines which intersected at the desired points, in a separate sketch, so you can snap the spline points to those intersections.

You can then dimension the tangency angles to the underlying lines, and finally dimension the lengths of the tangency handles to adjust the weighting.

This represents quite a lot of somewhat exacting work, and is possibly not a viable proposition unless you only have a relatively small number of profiles to build.

lawrence_rosdobutko

Might I ask then, how best would you recommend working around the limitations of the spline function? If it helps, I'm sketching the outline (and later the interior routes) for a custom electric guitar. I'm very familiar with Maxon Cinema 4D and thought that splines would be the best way to go about sketching this particular shape in OnShape. Would you recommend a different way?

andrew_troup

@lawrence_rosdobutko
I don't know of a better way than the one I describe.

Onshape is in its infancy, and curvy shapes based on analytical geometry will doubtless receive considerable attention from the development team in due course, but at present I get the sense that they are trying to create a solid foundation, with emphasis on the creation of "primitive" geometry, 

lawrence_rosdobutko

I guess I can understand that. Thanks for the help then! I appreciate it greatly!