Need help with loft and guide curves...

[dwc]

I am in way over my head.
As some may know one of my projects is making 3d printed violins, that in the meantime are pretty good. My motto is that to sound like a violin it has to vibrate like a violin, not necessarily look like a traditional violin.
As a next step in controlling the vibrational modes I want to make the zone where the curvature on the belly goes from convex to concave to be a straight line. I could use a straight line guide curve, but I can't figure out how to do that. I need to be able to make splines coincedent with the straight guide curves at several levels. But how? The guide curves will be determining the final curve form of the splines. I need to be able to find the point where the guide curve goes through a sketch plane and modify my spline at each level so that it does go through that point.

I have made a volumetric model using plain extrudes instead of a loft to show what I am looking for. The straight "fins" show where the guide curve should be. But even there I can't find a way to get the points where the guide curves cross each plane.

Many thanks in advance for any help you can give me.
Don

 

[Ex Machina]

The way I would do it is:

I would create the straight lines, I would use a 3D sketch but you can also create the appropriate plane and draw the line on there,
then I would create an axis from that sketch line with the "axis from line" sketch tool
Then I would create the planes onto which these splines will be drawn.
Finally I would create point where the plane and the axis intersect.

You can then project that point into the spline sketch and make it coincident with your spline. I can't test it right now but I think this method would work.

P.S. Amazing Looking violins!!!

 

[dwc]

Thanks Konstantinos, I will try that.
Don

 

[dwc]

Great !
I've got it working for my simple method test, now on to the real stuff.
One further question, is it really only possible to constrain to the end points of a spline? And if so, how can I ensure a continuous smooth curve through the end points of two successive splines? I though maybe a tangent constraint, but AD doesn't seem to think that is a good idea.
I am worried about introducing unwanted cusp points at the end points that might throw the loft.
This violin loft is a bit much for AD, it needs lots of tweaking to get it to work.

 

[Ex Machina]

Hey Don,

Check out this video I've made:

It involves using 3D sketch. The problem is that the loft command will not accept a 3D sketch as a guide curve (I think, give it a try). If that doesn't work, start the 3D sketch, get the spline tangent with the method I show here, and then project it into the 2D sketch of the guide curve. You will not see the tangent constraint but it will be tangent.

 

[NateLiquidGravity]

You can use a 3D sketch for the guide curves if you want.

 

[dwc]

It works with a 3D sketch.
I did the inverse of what you said (by mistake) first putting in the axis, then the points where it crosses the planes and then drew the guide curves between the points on a 3D sketch.
My remaining problem is putting constraints on a spline, but if it has to be I will use several splines and constrain the end points as that seems to work.

Thanks for all the help and tips. Although I have been using AD since V10 I have never used a 3D sketch before. There is still lots for me to learn.

For some reason I am not seeing your video.