Another inverted normals issue

Discussion in 'Design and Modeling' started by PeterHermans, Mar 18, 2009.

  1. PeterHermans
    PeterHermans New Member

    I'm having a problem with my car model, continuing on from this topic.

    Magics shows there are no errors (although overlappig triangles are tolerance dependant) but whatever I try the Shapeways validation says there are inverted normals.
    I could be wrong, but unlike overlapping triangles that are considered overlapping or not, depending on tolerances, normals are either pointing one way or the other... so where is the error?

    Is it in the model, but magics cannot detect it?
    Is it in magics, wrongfully saying the model is ok?
    Is it in the shapeways validation?

    Note: I first tried uploading different versions that were hollowed out, with the same result.

    Daddymack tried helping me out, but so far no luck.


  2. bartv
    bartv New Member
    Hi Peter,

    could you send the latest version of your model to in STL? Then I'll check it out for you.


  3. ArMOO
    ArMOO New Member
    Hi Peter,

    If you and Daddy can't fix ..............
    My compliments for your cardesign, very nice.
    Did you model it in Rhino?
    Aparently everthing is perfect. Did you try to delete the inverted triangels and fill the holes? Its one of the last steps you can do but maybe you should do it from the start.
    Just a guess.

    Greetings AO
  4. PeterHermans
    PeterHermans New Member
    I finally got it to pass the validation \o/.

    I got a screenshot from Bart, from Shapeways, that showed errors in Blender.
    I played with the tolerances for overlapping triangles in magics to reproduce this image. Note: I did not succeed in fully reproducing it. With the lowered tolerance settings I worked on removing some errors that were now detected. Today I checked the model in meshlab and had it remove 6 non-manifold polygons that magics apparently did not pick up. Then I went back to magics and rechecked and fixed the remaining errors.

    Good news: it worked
    Bad news: this is not a fixed procedure that will guarantee success the next time.
    We really need more info on the shapeways validation settings so we can find out where the errors are and fix them.

    I modelled it in Cinema4D, a couple years ago.
    There are/were no inverted normals; otherwise I would flip, or delete and refill them.

    Here's a rendering:
  5. frankbuss
    frankbuss New Member
    Nice car! I had the same problem with inverted normals. I used ViaCAD and only solids and boolean operations, which worked. Then I added some extruded text, which I assume ViaCAD would create correctly without inverted normals, but it didn't worked. For another model text works. Maybe it has to do with too fine details? I can try to reproduce the problem, if this helps the support but would be easier, if Shapeways could say in detail how the verification process works.
  6. ArMOO
    ArMOO New Member
    Hi Peter,

    Stunning design. Really nice car.
    I also noticed last weekend that screwing up the resolution of my model causes more triangels and as a result of that also more problems. Since the triangels are related to the normals ( if I understood well ) then less triangles might be the solution. I also found triangel problems if angles are to sharp or not tangent.
    I worked on a fairly complex model with alot of small radi and curvature. I didn't want to loose the detail and took the highest possible resolution, keeping in mind the maximum mb for uploading. It was impossible to clean the file.You end up deleting triangels and at the end you're destroying the model. So I think if you use solid works just stick to the setting fine when you export your file.
    Magics has a feature where you can reduce the triangles.

    I also noticed that accutrans can't scale binaire stl.
    It does scale asci stl. I make the stl 's in Solidworks.
    Am I right or wrong?

    Greetings AO
  7. PeterHermans
    PeterHermans New Member
    @AO: I'm sorry I'm not familiar with Accutrans.

    The prints arrived yesterday:
    see this topic.