shell offset question

Next
 From:  wimverbe
7684.1 
I have 3 planar polygons joined together, and want to turn them into a solid by using the shell offset command.
but the corners are funny and it does not become a solid but a joined srf.
how can I get a solid with correct corners?
Attachments:

Image Attachments:
Size: 20.1 KB, Downloaded: 11 times, Dimensions: 349x422px
Size: 15.4 KB, Downloaded: 8 times, Dimensions: 197x400px
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  Michael Gibson
7684.2 In reply to 7684.1 
Hi wim, see here for an explanation of why Shell does not currently work for thickening this kind of open surface structure:
http://moi3d.com/forum/index.php?webtag=MOI&msg=1939.10

Also some explanation here on why it can be more difficult to try and thicken an open surface like this rather than shelling a finished solid:
http://moi3d.com/forum/index.php?webtag=MOI&msg=133.11

Basically with a set of open surfaces if you've anything other than planes at 90 degree angles to one another, when you try to offset just some open surfaces alone they don't naturally meet up in a simple vertex structure, if you instead shell a solid some pieces of the solid can be used as "side walls" to make stuff come to a common cutting surface.

So the easiest solution for your case here is to make a complete solid and then pick faces as openings to use in the shell, that way shell will be able to use the "side walls" of the solid to make pieces meet well:

With a solid like this (see attached 3DM file):



With those 3 faces selected to make openings, you can then run Shell and get this kind of result:




You can get more of a sense why your original attempt on thickening the open surface made up of several angled pieces is kind of complicated by using Edit > Separate on it and then using Construct > Offset to offset each individual surface, you can see how the simple offset of each individual surface do not naturally connect with each other:




So it generally works better for something like this to make a finished solid rather than an open surface, and then run shell with the faces you want to have as opening selected. For shelling an open surface it only really works when you've got a single surface, or if your open surface is made up of all surfaces that are smooth to one another or are all at 90 degree angles to one another, those are the only situations where the vertex structure of the offset will match the vertex structure of the input.

Hope this helps, - Michael

  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
 From:  wimverbe
7684.3 
Thanks again Michael!

oh I love this software!

wim
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged
 

Reply to All Reply to All