external nodes

[jerrylucas]

Hi!

I have a modeling question. I have an arbitrary figure created only with nodes and without elements. How can I choose the external nodes?

Thanks.

 

[meshparts]

Simple question, complicated solution.

In my opinion, without programming, you cannot solve it. I read on Internet about a algorithm on 2d who can find the external nodes of o nodes cloud. Should work in 3d too. But I don't remember how is the name of this algorithm...

Regards,
Alex

 

[koslo]

I don't think that this is effectively possible without having the connectivity. Take this 2D model for example, given these nodes:

.     .     .     .



.     .     .     .



.     .     .     .



.     .     .     .

How do you know the exterior is not like this:

______       ______
|     |     |      |
|     |     |      |
|     |_____|      |
|                  |
|                  |
|                  |
|                  |
|                  |
|                  |
|__________________|

-Jim

 

[cbrn]

Hi,
yep, but I suspect the O.P. wanted to refer to convex domains (otherwise there is no algorythmic possibility to determine the "external" nodes). For convex domains I remember that there is an algorythm for that. Sorry I don't remember where to find it...

Regards