The polysurface offset fails in Rhino WIP.
elmo(1).3dm (4.4 MB)
The offset works only on individual surfaces, and even in that case the edges do not align properly.
Anyway, I manually fixed the single surface.
The offset works only on individual surfaces, and even in that case the edges do not align properly.
Anyway, I manually fixed the single surface.
this is, I hate to say, expected behavior from the offset tool. To be clear, expected, not desired.
what is your ultimate goal from this model? Are you printing, cnc machining, etc?
or do you just need thickness for a rendering?
if you need thickness for a rendering, you can use the thickness render modifier in properties.
if you are printing, shrinkwrap shelling would be a great option.
if you want to cnc or need a nurbs out put, quadremesh with a subd conversion and then offsetting the subd may be a path forward.
or one of my old professors used to say, “sometimes to do the work, you just need to do the work”
and offset the whole shebang, and then repair the result as needed. The upside of rhinos offset is it gives you something as opposed to a offset fail in solidworks which simply just says “no”
Is this ideal? no…Ideally we’d love it to work brilliantly, but this is where we are.
I’m modeling a medieval helmet intended for 3D printing.
The helmet is made of multiple functional parts — visor, bevor, and aventail — which are mechanical, moving components. These parts must slide, rotate, and fit together precisely, so a proper surface offset is not optional, it’s required for functionality.
So yes, I agree with you: having an offset, even imperfect, is better than having none.
However, what I don’t understand — and this is the core issue — is the inconsistent behavior of the tool: the offset works correctly on a single surface, but fails or behaves unpredictably when the same geometry is part of a polysurface.
Even though this is a personal project, my approach is industrial: I usually design parts intended for molding, so even here I’m already taking into account undercuts, draft angles, and how the part would be released from a mold.
The polysurface has several creases where there is only G0, not G1, continuity between adjacent surfaces. That can cause challenges when offsetting because the basic offset of a surface moves the edges normal to the surface. Across the crease the normal direction changes which means the edges of the basic offset surface do not coincide. This requires extending the surfaces and then trimming the surface to each other. Depending on the geometry that can leave gaps which need to be filled. Also extending a surface with edges that end in a cusp can have problems.
Yes, in fact I had to extend the surface and, in other areas, trim it to eliminate undercuts.