Help with TopMod

Discussion in 'Design and Modeling' started by Camazine, Aug 17, 2011.

  1. Camazine
    Camazine New Member

    I have been working on a model in TopMod for which I have attached several pictures. The first picture is the model as it appears on the Shapeways page:

    You can see that the central portion of the model is missing. If you view the .stl file in MeshLab or Netfabb, you can see the missing portion shown in a different color.

    Can anyone tell me what is going on? What is wrong with this .stl file. And how do I repair this issue?



    Attached Files:

    Last edited: Aug 17, 2011
  2. virtox
    virtox Active Member Moderator
    Different colors usually denote different normal orientation.

    So the "black" part as viewed in Meshlab is inside out.

    For a proper model definition all normals should point to the outside.

    In this case the Meshmedic subtracts the inside out portion from your models in an attempt to fix it.

    I tried fixing reorienting the normals in Meshlab, but it did not work.
    Also ran it through Netfabb cloud but it also cuts out the inverted part.

    Perhaps you can manually fix it by selectin only the wrong part and do an invert normals.


    Last edited: Aug 17, 2011
  3. virtox
    virtox Active Member Moderator
    Ah on closer look, the inside out parts is caused by the model self intersecting. That is why automation fails to fix it, as the model is manifold, but turns inside out on the inner part.
  4. Camazine
    Camazine New Member
    Well now at least I know what is going on! (That's what I thought was happening, but I had no luck either trying to fix things in MeshLab or Netfabb -- but I really am rather new to those programs, and figured it was just my ignorance.)

    Now my question is how do I select just those areas with the inverted normals? In Netfabb, I see that I can select individual triangles and even expand the selection, but I do not see any way to select all the triangles that need to be flipped.

    Am I missing something obvious?

  5. Camazine
    Camazine New Member
    Wow! Now you are talking way out of my understanding. Can you explain that in a simpler way for someone who is rather new at this. I am rather lost about "self-intersecting" and "manifold"

  6. virtox
    virtox Active Member Moderator
    Haha, yeah, sorry about the techno-babble ;)

    Regarding manifold, best to google a bit ;)

    But your model is in fact a single closed surface or shell.
    So software does not see anything wrong with it and can't discriminate between bad and good sections.

    Regarding self-intersection:
    At the border of the color switch in your netfabb image, is where the top part of the surface goes below the bottom part.
    If you would look at a cross-section it looks like that christian fish thingy ;)
    Last edited: Aug 17, 2011