I made a sweep with an arc and 2 freehand rails and then used the Shell command and it works. I can't do the same thing with Network surface.Is this normal?

Hi JTB, normally I wouldn't expect that. But often a Network surface can end up with a more complex control point structure which I guess could affect some other operations such as shelling.

Can you please post a model file with those curves in it so I can take a look? It is possible I can tune things up to work better.

- Michael

Here it is...

Hi JTB, in this case it looks like your resulting surface has some corners that fold back over themselves. Like for example in this spot here:



That's actually a corner point of a 4-sided surface at that spot, but the control points near that corner are rather jumbled around - this type of situation will tend to mess up the calculation of an offset surface (which is part of the shell operation), because it causes the surface normals to wildly flip around at that fold-over spot.

Surfaces need to have somewhat more of a regular grid layout with a more distinct corner to be able to be offset.

Also, normally you want to try and have your input curves to the Network surface be touching each other. I did some work so that you could get some results without requiring exact touching, but in this case your curves are really quite far away from each other, that will tend to make less predictable results.

You can get better results for this type of a shape if you try to make a slightly larger, more rectangular shaped layout of your curves to start with, and then trim away the excess outer portion of that rectangular patch to get your smooth exterior outline.

- Michael

Thank you Michael.

Hi Michael,

These curves produce a smooth single surface in Rhino as a network surface.
They do work in MoI with a 2 rail sweep and a scale rail as a polysurface, but there are some creases.

Are there a certain number of curves that work in MoI's
network surface or a particular orientation of curves that is more conducive to smooth surfaces?
Rhino has that option to sort curves by direction when they are going every which way..
I can't usually get it to work, but at least I know the direction is the problem, then. ;-)

Jesse

Hi Jesse - your "central rail" there is not entirely smooth - it comes to a sharp point where it starts the upward bulge. Generally those types of sharp points are not going to work well in a scaling rail.

Your network layout is very clear there, MoI is not getting confused about the directions, instead it is having a hard time combining the multiple curves together into one single surface, the resulting surface is getting too dense. I should be able to do some work that will help to solve this and also for other areas that combine multiple curves together into a single surface such as loft and sweep.

I thought a bit about putting in some sort of "manual direction" picking like Rhino has an option for, but I haven't yet seen the type of network that would need it. I'll add it later if something like that shows up, but I think that anything that can't be sorted automatically probably won't be a valid grid network for this command anyway.

I tried your curves in Rhino, and got a nice smooth surface result, but it is also a bit strange in a couple of aspects, it seems to ignore the sharp corner in your central section, and seems to sag away from some spots nearby that by more than the allowed tolerance:



Do you think it is better for creases in your input curves to be ignored like this and sort of automatically smoothed out?

I kind of would expect for there to be a crease in the resulting surface corresponding to the crease in your input curve...

- Michael

Hi Michael,

This was originally a Rhino model. I put the sharp angle
in there to replicate a jade ring that someone wanted
redesigned for a faceted stone, but I agree that it's not
consistent with the rest of the design.

My curves from last year weren't smooth...I just drew them over
in MoI using blends and G3 fillets...the sweep turned out a lot better, perfectly
actually. :-)


The option to smooth creases in surfaces might be good.
I know you want to keep the "tinkering" aspects of modeling behind the scenes in MoI,
but the ability to rebuild with a certain number of control points is useful when the default sweep settings aren't producing the desired result.


Jesse