Parts of model disappeared

Discussion in 'My Work In Progress' started by mjrbaseball, Feb 3, 2013.

  1. mjrbaseball
    mjrbaseball New Member
    I am puzzled. When I uploaded the dae file to Shapeways, it was accepted, but parts of it disappeared. What confuses me most is that the parts that are missing are actually thicker than parts that showed up. Why did this happen, and what can I do to correct it?

    Here is a link to my model. It is supposed to be a set of bleachers, like at a ballpark. The posts showed up, as did the safety rails, but the seat planks and foot planks are gone.

    I can send someone the dae or original Sketchup file if they want to check it out.

    Thank you.
     
  2. stonysmith
    stonysmith Well-Known Member Moderator
    Open it in Netfabb basic (www.netfabb.com) and see if those seats have inverted normals.
    You might also run it thru cloud.netfabb.com to ensure that it's a single mesh.
     
  3. mjrbaseball
    mjrbaseball New Member
    It is a .dae file, not .stl. Also, I do not know what "inverted normals" means.
     
  4. mkroeker
    mkroeker Well-Known Member
    Get meshlab (also free) to convert your dae to stl. You can also check and correct the orientation of the face
    normals in this program. Basically if the face vertices are listed in the wrong order, the normal vector pointing
    away from that face points to the inside of your object. Such misoriented faces are a sure way to mess up your
    model, as the automatic repair that shapeways attempts on upload will throw away those parts that have no
    clearly defined outer surface.
     
  5. mjrbaseball
    mjrbaseball New Member
    I have Meshlab, but is a very complicated program. Converting the dae to stl did not help. I do not know what face normals are. Where can I learn how to check the factors you mentioned? Or could someone please test my model to help me see what is wrong with it? Thank you,
     

    Attached Files:

  6. mjrbaseball
    mjrbaseball New Member
     

    Attached Files:

  7. stonysmith
    stonysmith Well-Known Member Moderator
    Face Normals: every surface on your model is made up of triangles. Pick any triangle A,B,C and (conceptually) lay it on the floor. Then walk from A to B to C. If you are walking in a counter-clockwise direction, then the Face Normal is "up". If you are walking in a clockwise direction, the Face Normal is "down". (This is also called the "right hand rule")

    On a 3d model such as a solid cube, you need for all of the face normals to be pointing "outward" from the center. If even one of the face normals points inward, (the corners are in the wrong order) then the model is considered to have a hole in it. Programs such as Netfabb Basic mentioned above can help you find such triangles and flip them so that they are pointing outward.

    ====
    Someone else may be able to chime in here and offer some assistance with Sketchup.. I'm not proficient with it.
     
  8. mkroeker
    mkroeker Well-Known Member
    Quick tutorial on using the repair function in netfabb is here (under "Tutorials" in the "Create" menu). I thought there was something similar for meshlab but cannot find it right now (and am in the wrong place now to just start meshlab myself) - I believe the equivalent meshlab function for displaying/inverting face normals was in the Filters menu.