Thank you very much for the detailed explanation. So, it seems to be, if I need Unfold3D, than I must direct use data from MOI3D. There is one problem: some times Unfold3D tell me, that something is wrong with the mesh and than, in the past, I tried to fix the mesh error in Rhino. If I get an error again I will post it - if I remember me right, the error was called a "butterfly point".

At the Unfold3D help page I found some infos about the mesh requirements. Is it possible to get meshes without butterfly points per MoI?

http://www.polygonal-design.fr/e_unfold/manual3_1v5.php

Hi Micha, for most mesh uses such as just rendering it for example, those "butterfly points" are not normally a problem, so MoI's mesher has not been designed to treat them in any special way or avoid them. They are not really what I would call an "error" in the mesh really.

But I would think it would be kind of unusual to get that situation, especially if you have a well formed fully closed solid it should not have any border edges at all in the generated mesh, so probably ensuring that all edges are joined and that you have a closed solid would be a good step to help avoid that kind of thing.

If you can give me an example that does generate one of those butterfly points, it would help me to understand the situation a bit more.

... Actually, if I understand the problem correctly, it may be that you have to avoid certain arrangements of geometry which are just not permitted by Unfold3D - for example how would you expect for me to avoid a butterfly point with a model that is set up exactly as the example shown in the Unfold3D page? I include an example file here - how would you expect for this mesh to be created without any butterfly points?

I suppose one possible solution is to have that butterfly point be a duplicated point instead of a shared point between the faces that touch there. Right now I have no provision for doing that, so if you need such a thing you should try exporting with welding turned off, then take that result mesh into a polygon processing program and weld all other points except for that butterfly point, that may eliminate it.

But it would probably be best if Unfold3D would just duplicate ("unweld") such points itself since it is sensitive to their presence...

- Michael

OK, I will send a link to this thread to the Unfold3D team -maybe they can do something.

Thanks,
Micha

Hi Micha, also next time you run into it, please try to post the model file or e-mail it to me at moi@moi3d.com if you want to keep it private, and if possible indicate the area that has this point in it. That may help me to better understand if there is anything I can do to avoid it, or possibly give you some ideas on how to fix up the model to avoid it.

But notice that page you gave for the Unfold3D docs says "Modeling rules" - these are meant to be rules that must be followed when creating the model.

If the people who created your original model did not follow those rules, then I guess that model is then not suitable for Unfold3D - you would need to show those modeling rules to the people who create the model to make sure that they don't create an unsuitable one.

I understand that is probably not practical for you to actually be able to do in your particular situation, but following these rules during model creation is what is intended to be done for use with Unfold3D I think.

Remember - MoI's mesher does not have artifical intelligence and is not generally intended to alter the topology or overall structure of a model that you give it to mesh - on the contrary, it generally tries to follow the topology and structure that it is given as best it can.

If you need a topology to follow special rules, if you give the mesher a model with topology that breaks those rules you will then probably get a mesh that also breaks those rules.

Again, remember that saying "garbage in, garbage out" - if you input objects to the mesher that are not configured properly for what you want, probably the exported mesh is not going to be configured properly neither.

- Michael

Hi Micha - one other note on "butterfly points" - maybe these could also happen if the mesh that MoI exported did not get completely welded.

One thing you may want to look at is if your base object is of very small or very large size in units. I mean for example if your entire model is something like 0.03 units across, or 100000 units across, either of those can cause some problems.

If you try to get your model to be a more consistent size more like 10 units across instead of very large or very small that may help various things work more smoothly and may have points welded better.

Just another possible thing to look at anyway.


Probably a lack of welding is what would be generating your butterfly points in most cases rather than a completely unsuitable modeled topology. Another big thing to check though is whether your object is a closed solid or not, if it is not a solid then some edges of it are open edges which will then generate open border edges which is part of what makes a "butterfly point". So that is another big thing to check for.


Objects of a very small or large size can be harder to get automatically joined into a solid when imported from IGES or something like that.


- Michael