I’m trying to draw a 3d surface reflecting the negative shape of a violin. It will be lated machined with CNC on wood.
I have the violin contour, and 5 depth curves. What would be the smoothest method to do this? Below are some images. Thanks in advance!
can you get 2-3 curves in direction perpendicular to the one you have?
If so, you can use surface from network of curves command. But you’ll need to explode the closed curves shown on the pictures and use only the curve that defines the shape of the surface.
Do you want the surface to go through these curves, or they will act as controls?
Could you upload the file with the curves or similar. With the contour of the violin (or similar). This way we can try and give you a solution approach.
You can’t really do that if you don’t have more curves.
If you rely only on the curves provided, in the middle area where the sharp edges are you’ll get gaps. I think Patch does the job pretty well. If only there were more curves at the critical locations especially.
I model similar shapes often and find that while patch through 4 or 5 cross sections will give me a smooth shape with no creases it will often deviate more than i want from a co planar perimeter, and not follow my design intent sufficiently even if the surface is modeled larger and trimmed back to your final outside shape afterwards. Networksrf and even a series of adjacent sweep2 surfaces with tangent continuity can follow your design intent more closely but i often need to smooth out the surface afterwards to get rid of little creases, ripples and dips that can show up when your cross sections are followed too closely. So i often model for accuracy first then run the contour command to generate a relatively dense series of cross section wires in both x and y axis-maybe 5 mm spacing. Then i run the patch command through this denser network of wires to “relax” the surface a little but still not deviate too far from my original design intent. You can play around with contour and patch wire density to get the balance you want between accuracy and smoothness.
Don’t expect to generate viable violin top plates from that little information you have. If you understand german, you may try look into the Institut für Musikinstrumentenbau in Zwota (www.ifm-zwota.de) they did some research in CNC machining back in 2006. They even used Rhino to reverse engineer the surfaces.
The actual plate geometry is way more complicated. And the geometry defines the sound so you may want do get it right.
as it was explained to me by the customer, those depth curves are the ones used as templates for handmade violin. The mould i’m trying to make here is an negative mould of the back plates so she can place the plate and carve the inner side, so it doesn’t have to be perfect. Great data though! i’m not fluent on german but I’ll check it
As a template for further manual tuning, you don’t need a lot of detail. In fact it’s probably better to leave room for the work.
Precision should not really be an issue, as you can expect the whole surface to be retouched. I think @Stratosfear’s approach is probably the best. It gives you a simple and good quality surface and closely resembles the original process.