Hi plish - part of the Inset process involves calculating offset surfaces, and with a kind of chaotic surface like you are showing there with a lot of little bumps and wiggles it makes offset surface creation very difficult.

Part of the process of Inset involves doing offset calculations of the "side walls" around the inset face.

Basically an offset surface is a new surface that is created by tracking along the surface normal by a particular distance. It's sort of like sticking a pole on the surface and moving it around and making a surface tracking along at the other end of the pole. When you have a lot of little bumps and wiggles in a surface, you can imagine that the movements of the "end of the pole" become magnified, and it's easy for the result surface to become self intersecting. Once that happens it will then cause further problems because surface/surface intersections will have problems when self intersecting surfaces (surfaces that fold back and forth over themselves) are involved.

So the geometry that you have there with lots of bends and wiggles in it, is just generally unsuitable for anything involving offset calculations, so probably anything under the Offset set of commands (Offset, Shell, or Inset) will not be functional with that kind of geometry. You will need to create cleaner and less wiggly geometry in order for Offset, Inset, or Shell to really have much of a chance of working at all.

Just in general NURBS modeling is not good at making shapes with lots of little lumps and wiggles in it. If you need to do stuff that's shaped like that you would be better off using a polygon modeling package instead where you can do sub-d modeling, those programs are more focused on making organic shapes. MoI is much more focused on making sort of smoother semi-mechanical type shapes.

It is possible to make lumpy/bumpy/chaotic shapes for some purposes, but just as you've seen here there will be many areas of the toolset such as offsets and also booleans (when you have self-intersecting surfaces) that will not be usable with such geometry. That's a generally expected consequence of that kind of geometry.

- Michael

Also Filleting involves some offset calculations inside of it as well, so often times Fillet will also not work on chaotic lumpy things like that as well.

Booleans will probably work as long as the surfaces involved are not actually self intersecting.

The big problem really is in areas like indicated with the red arrow here:




You've got such a tight bend in both directions of the surface in those areas that hardly any offsetting at all will have the offset result end up sticking back through itself, once that happens it's very difficult for various other calculations to work on it very well.

It could even be possible that your surface there is actually self-intersecting already even before any offset is applied to it.... I can't be entirely certain by just looking at a screenshot. By the way it helps a lot if you can post the 3DM model file of the stuff you are asking about instead of just a screenshot, because 3DM files can be closely examined and looked at from different angles, etc... which is not really possible to do with a screenshot.


Here's an example of the kind of messy results that an offset of a relatively large amount will generate as it goes around a tight bend:





If your shapes are set up in such a way that will cause this kind of self-intersecting / bunching / self-crossing type results during part of the calculation it will generally not work, so this is generally a situation that you should try to avoid.

If the models that you need to build are typically full of lots of wiggly bumpy surfaces like this, that's usually a sign that you're not really using "the right tool for the job" - that kind of stuff is better suited for either a polygon modeling program or a brush sculpting program like ZBrush, and not a precision drawing / CAD type program like MoI. Depending on what you are doing sometimes it can work well to use MoI to build some initial broad smooth forms and then use ZBrush to add little detail bumps and engraving as a separate stage though.

- Michael

Michael,

I was basically pushing the envelope with what I could try to do. It's not typical for the work I do but I enjoy playing ;-) I did find out that fillets didn't work either ;-)

The inset I was doing only went down to the line near the top. Sometimes I can take that top part off and it reveals a surface that I can thicken up to create the inset. It looks like the valleys/peaks between squiggle control points can't be less than the thickness (or twice the thickness) of the wall on the inset. And as you said, the depth can go into the funky bend areas or things just go to pieces.

As always, thanks!