Home »  » 3D Printing » Question on model topology
Search Search  
Show: Today's Messages    Show Polls    Message Navigator
Question on model topology [message #67708] Thu, 09 May 2013 17:09 UTC Go to next message
avatar chasecoop  is currently offline chasecoop
Messages: 2
Registered: November 2012
Go to all my models
Junior Member
Hello, I'm a bit new to 3d printing working on my first print. I currently work in the vfx industry, so we have a lot of rules for geometric topology that seem like they can be broken in 3d printing a bit (and I'm learning the 3d print rules as I go).

So my question is:

I downloaded a 3d model as an example: the "batwingMinimalSurface", and noticed it had a lot of overlapping geometry/cvs/faces when you seperate it. And on that note, noticed it was a combined 3d model to beging with.

Is this legal in 3d printing? Can the printer handle this type of overlap with geometry and components? (see attached image)



Thanks

Re: Question on model topology [message #67710 is a reply to message #67708 ] Thu, 09 May 2013 17:24 UTC Go to previous messageGo to next message
avatar Youknowwho4eva  is currently offline Youknowwho4eva
Messages: 5314
Registered: September 2008
Go to my shop
Senior Member
I work here
Intersecting geometry can be printed. Overlapping can cause issues in the automated healing process. You can upload to see how the render comes out, if your model successfully uploads. You can also use NetFabb basic to removed double triangles


Your friendly neighborhood Moderman
michael@shapeways.com
Re: Question on model topology [message #67715 is a reply to message #67708 ] Thu, 09 May 2013 17:36 UTC Go to previous messageGo to next message
avatar AmLachDesigns  is currently offline AmLachDesigns
Messages: 1155
Registered: September 2011
Go to my shop
Senior Member
Each component you create must be a closed volume with correctly aligned Normals.

A cube is a closed volume. If you remove one face without adding thickness to the remaining faces it is not.


If you want to create a model from components, then the components must overlap even if it's a tiny bit. You can join them into one model or upload them grouped together and Shapeways will join them. There must be no non-manifold parts (explained here in this slightly out-of -date page).

Now I know this probably raises more questions than it answers, but it should give you a place to ask more questions from....

Good luck!

Re: Question on model topology [message #67721 is a reply to message #67710 ] Thu, 09 May 2013 17:56 UTC Go to previous messageGo to next message
avatar chasecoop  is currently offline chasecoop
Messages: 2
Registered: November 2012
Go to all my models
Junior Member
Good to know thanks. Now my question is, since you can have overlapping geometry printed, what does the printer do with that overlapping geometry? Say for instance you have two volumetric spheres intersecting and then combined into one piece of geometry, but the vertices are not actually connected - does it just mold that geometry together where the intersection is happening?

Re: Question on model topology [message #67723 is a reply to message #67708 ] Thu, 09 May 2013 18:02 UTC Go to previous messageGo to next message
avatar Youknowwho4eva  is currently offline Youknowwho4eva
Messages: 5314
Registered: September 2008
Go to my shop
Senior Member
I work here
The automated software automatically joins intersecting geometry. This process can cause a mess with overlapping geometry though. Intersect is fine. Face to face is no good.


Your friendly neighborhood Moderman
michael@shapeways.com
Re: Question on model topology [message #67765 is a reply to message #67723 ] Fri, 10 May 2013 08:31 UTC Go to previous messageGo to next message
avatar timcastelijn  is currently offline timcastelijn
Messages: 4
Registered: March 2012
Go to my shop
Junior Member
Hi everyone,

I have a question regarding the overlap as well. I created an array of cubes, translated over y-axis and rotated over z axis. which meas they overlap and all the cubes' bottom and top faces are in exactly the same plane. Is this what you refer to as "no good" Michael?

The model looks OK in the upload section (it is a test - do not worry, I won't print $2800 worth of messy geometry Smile ), however I can imagine that face-face intersections in the same plane are causing problems I cannot see. I can not join the objects in a CAD-package before uploading, as I want to use a script to create meshes.

best regards, Tim

[Updated on: Fri, 10 May 2013 08:32 UTC]

Re: Question on model topology [message #67770 is a reply to message #67765 ] Fri, 10 May 2013 10:46 UTC Go to previous message
avatar AmLachDesigns  is currently offline AmLachDesigns
Messages: 1155
Registered: September 2011
Go to my shop
Senior Member
timcastelijn

Generally, if things a) upload ok, and b) look ok in the SW render, they are ok.

Check out the link I posted before for non-manifold issues.

The case that youknowwho4eva is describing (I think) is where you bring 2 cubes together so that 2 faces exactly touch, i.e. the faces are in the same plane but do not overlap at all. In your example the volumes intersect so that is ok. Either yo or SW need to Boolean the objects together and they must intersect for this to be possible.

 
   
Previous Topic:Printing in parts
Next Topic:SS won't appear as a printable media

Logo

Hello.

We're sorry to inform you that we no longer support this browser and can't confirm that everything will work as expected. For the best Shapeways experience, please use one of the following browsers:

Click anywhere outside this window to continue.