Is Shapeways 3D preview accurate?

Discussion in 'My Work In Progress' started by volundr, Nov 17, 2011.

  1. volundr
    volundr New Member
    I made a signet ring with an engraved design in SketchUp. The engraved bit shows up fine in SketchUp and exported (as OBJ) in AccuTrans. However, on Shapeways site, in 3D preview, I cannot see the engraving so I am wondering if it will show up on the actual item.

    Any thoughts?

    SketchUp image:

  2. volundr
    volundr New Member
    AccuTrans image:

  3. volundr
    volundr New Member
    Shapeways image:

  4. Youknowwho4eva
    Youknowwho4eva Shapeways Employee Community Team
    I want to say I see the image upside down on there. Without seeing the model, I'd say it's probably overlapping geometry (touching faces, not inside one another) or inverted normals. It looks like in sketchup, you have the emblem as a seperate piece as the ring, and that it's sitting perfectly nested. If that's true, I'd either extend the emblem faces so they extend into the ring, or join them.
  5. berky93
    berky93 New Member
    Shapeways seems to have a hard time handling N-gons with holes in them. Because the face of the ring is a single shape with the design cut out of it, it creates geometry that the site automatically fills in while attempting to make sense of what it sees. Simply adding an edge that extends from the edge of the front face to the edge of one of the objects, and more edges to connect all of the objects, should give it definable polygons that it can understand.

    I hope I put that in a way that is easy to understand, I can never tell :confused
  6. volundr
    volundr New Member
    I ended up removing some duplicate edges and raising the whole engraving part up a little. It showed up better on the preview this way. We'll see how it actually turns out.
  7. volundr
    volundr New Member
    Having a similar issue with another model. Exported it to STL this time, shows up correctly in a variety of 3D viewers (e.g. Accutrans), but different on Shapeways website.

    Accutrans view:
  8. volundr
    volundr New Member
    Shapeways viewer (note how the back has weird new triangles instead of smooth surface and circular indent in the center):

  9. volundr
    volundr New Member
    Attached is the STL file of that second object.

    Attached Files:

  10. berky93
    berky93 New Member
    I ran an stl check on your object in 3ds max and found a lot of errors. It looks like the way you modeled it was using booleans or some other method that produced a lot of intersecting polygons and n-gons (polygons with more than 4 sides) as well as concave surfaces and some odd triangulation. It's important to make sure you have proper geometry, especially when 3d printing.


    I recommend opting to start your models with low polygon counts and then protecting your edges so that subsequent smoothing operations give both sharp edges and proper, smooth curves. This will ensure your models are manifold and have proper geometry.
  11. volundr
    volundr New Member
    The model was designed in SketchUp. It is very simple: mostly flat walls and a couple of curves for the lens. What the export/import does to these models is mind-boggling.

    Camera Buckle 1i.jpg
  12. volundr
    volundr New Member
    Another view of the STL file (from Rhino 4). Looks fine here too.


  13. Youknowwho4eva
    Youknowwho4eva Shapeways Employee Community Team
    Your file "looks" fine in KeyCreator as well. But you have internal polygons. There are faces inside that will cause errors.
  14. berky93
    berky93 New Member
    Oh, yes, the model looked just fine in max. It was only after I ran an stl check that problems were evident (although by by simply looking at the wireframe you could see how the geometry sketchup exported has the potential to cause issues).

    The thing about sketchup is, because it is so simple and intuitive it doesn't give you a lot of control over the underlying geometry behind a shape. You can have huge n-gons or double faces with no problems in the program but issues upon export.
  15. volundr
    volundr New Member
    Well, I worked on this model for a while and I think it is in better shape now. Can someone please run a STL check for me to see if I goofed up somewhere?

    Many thanks!

    Attached Files: