About the lovely new inverted normals check

Discussion in 'Bug Reporting' started by chris89, Feb 28, 2009.

  1. chris89
    chris89 New Member
    Hey guys,

    The new inverted normal check is great, the more bug tracking there is the better.
    Though, i did notice a slight problem with it:

    The way i hollow out my models is by making an inside with the normals the other way, which effectively makes the models hollow and i can keep the minimum thickness everywhere.

    I have printed models that are made this way and they came out perfect.

    But now with the new normals check, whenever i upload a new model it says it cant be printed because it has inverted normals.
    I'm sure it is because of the insides, which shouldn't create a problem.

    Is there a way to let my models be uploaded and printed now with the new normals check?
    I'm a bit afraid i might miss out on the 25% discount because of this!! :(
  2. Whystler
    Whystler New Member
    Hey Chris,

    I don't know how quick a response you'll get from staff on the weekend, just because, well it's the weekend! :) If you are using 3D Studio max, I can tell you how to make your model hollow a different way if you like.

  3. loonsbury
    loonsbury New Member
    Depending how you hollowed, it's not because of the inside faces, at least that was the case with mine. As long as your normals all point outside the material (towards the empty space) it should be ok. My exported models had poorly modeled interiors for their mouths (that are completely useless in the game, oddly.) I cut out the mouths and closed the lips together more precisely, and then it worked... Here's hoping it's something similar for yours.

    I was very very worried that the inverted normals check would kill me, but it seems like it may be more accurate than it sounds.
  4. chris89
    chris89 New Member
    hey whystler, any help would be appreciated :) and new techniques as well of course.

    Loonsburry, the problem i am facing with my current models is that it seems to recognise the hollow inside as a mesh with inverted normals. They are supposed to be pointing inwards otherwise it would be a mesh inside a mesh, instead of the other side of the "shell" so to say.
    hmm it's a bit difficult to describe in words, i'll see if i can get an example up.
  5. loonsbury
    loonsbury New Member
    Is there an exit hole? That may be the whole problem... My hollowing faces inwards as well, maybe I'm just misunderstanding you.
  6. daddymack
    daddymack New Member
    Hmmm... naturally I uploaded soo many models to be printed with the discount :D I spent half the day refining and reprepping models for upload... My inbox is sooo full of 'there is a problem with your model...' I've redesigned the penholders and they were a major culprit.

    My findings were (eventually) that I had some surfaces passing through each other, just as the emails stated... Sometimes when a surface is offset it will pass through itself ever so slightly, especially anywhere there is a corner. The normals checker is very sensitive and was able to find the tiniest of errors in my model. As frustrating as it was initially, all my models got thru and I feel reassured that they will print perfectly. I might show some examples of my findings to clarify them later today
  7. chris89
    chris89 New Member
    Ah i think the problem i am having is what daddymack described. Some faces of the elements that intersect making the normal at that point pointing outwards.

    Ugh, it's too much too fix that quickly :( already been on it the entire day. Ow well guess i'll just go without the discount then and take some more time to fix this.

    I did a quick test importing with flipped normals on purpose, and it said the model was printable XD kinda made me laugh a bit
  8. daddymack
    daddymack New Member
    Hi Chris89, you can send it to me if you want and I'll have a look

    here's a 30 second tutorial demonstrating the basic problem and how to fix it


    Hopefully that helps a bit

    Chris89, my email can be found on the contact page at mack3d.com if U want to send me yr file (.obj)
    Last edited: Feb 28, 2009
  9. chris89
    chris89 New Member
    ah yes, that's what i've been doing all day.
    Thanks for the little animated tutorial :)
    I'm doing it for someone else though, so i will ask his permission to send the file to you. Here is a little preview of the "hell"

    Last edited: Feb 28, 2009
  10. daddymack
    daddymack New Member
    nice model bro, it will be a challenge getting a good internal wall and keeping the polycount under the 500k. What size are you planning to print it at?
  11. chris89
    chris89 New Member
    The plan was 12cm in height.
    Luckily most of the shapes are just round and not with any detail, so getting it under 500K with an inside wasn't a problem.
  12. chris89
    chris89 New Member
    ARgh, turns out the major area of error was 3 seperated polys that got seperated by the optimization :(

    Thanks again for all the help guys, it did help a lot, and i will have more stuff on my checklist for my next models.

    I'll post images when its printed.

    cheers again.
  13. loonsbury
    loonsbury New Member
    On the inverted normals topic, I would like to be able to check for this before uploading, so as to save time and stop putting load on the Shapeways server.

    As far as I know, there isn't a check that works the same way in Blender at least; does anyone know if there is a function for this, or another tool to use?

    If this isn't feasible, could we get problem visualization for inverted normals? I know I'm demanding, but I'm also lazy... :D
  14. chris89
    chris89 New Member
    this would be really nice indeed, since there's no specific tools for this in most 3d software.
    or you'll have to show normals on the mesh and run through every face, and even then it will be difficult.