Having issues with a model..

Discussion in 'My Work In Progress' started by Ray716, Jan 15, 2011.

  1. Ray716
    Ray716 New Member
    So a while back i wanted to do a few rings by making a profile and spinning it into a ring. I liked 2 that i came up with. The first uploaded great, the 2nd, not so much...

    It's water tight, all the normals are facing out, and there is a low amount of polygons, 262080, And i thought the tolerances were with in reason. Can someone take a look and help me figure out what i did wrong?

    thanks in advance for the help!


    Attached Files:

  2. TurtlesAreCool
    TurtlesAreCool New Member
    262,000 polygons is definitely not low. Also, that number is not the number of polygons in your model but the number of vertices. Your model has over 500k triangles - that's why your model won't print. Your STL looks fine other than that. I have reduced the vertices in your model through the following steps:

    1. Opened your file in netfabb and saved it as an .obj
    2. Imported in Blender and applied a decimate modifier.
    3. Exported as .obj and reopened in netfabb to convert to STL.

    I used a decimate of 10% (meaning that 10% of the original faces are kept). You could still go lower for your model, since the shape is not very complex. In any case, the decimate modifier is not the best, so it is better not to have to use it if possible - try to end up with fewer than 100k polygons in the future.

    I tested the revision on http://cloud.netfabb.com/, so it should upload correctly.

    Attached Files:

  3. virtox
    virtox Active Member Moderator
    TurtlesAreCool is right. polygon count is above 500k.

    As an alternative you can also download Meshlab (it's free)

    Load up the stl,
    go to Filters -> Remeshing, simpli... -> Quadric Edge Collapse Decimation

    The standard settings usually halve the polygon count.
    Repeat if necessary.

    See attachment, not tested, but should be ok.



    Attached Files:

    Last edited: Jan 16, 2011
  4. Ray716
    Ray716 New Member
    Thanks for your help guys.

    So, i re did the spin with FAR LESS steps than i had.. didn't even realize i had that many steps.

    So my question now is, With Blender is the number of faces the number of polygons? Or is it something else?


  5. Magic
    Magic Well-Known Member
    I do not have the answer (I don't use Blender) but I can reformulate the question. The problem is, in Blender, is the number of polygons the same as the number of triangles. That is: are you making your models out of triangles or out of quads or even more complex polygons?
    The Shapeways's 500k limit applies to triangles because the STL format convert all the polygons into triangles.

    A way to understand if your modelling tool is displaying the number of triangles or the number of polygons is to compare this number to the number of vertices.
    - If the numbers are of the same magnitude then the odds are high that you've got a number of triangles.
    - If the number of polygons is roughly half the number of vertices then it is very likely that you got the number of polygons and that those polygons are quads.
    - If the number of polygons is even lower than half then those polygons are more complex than quads and are definitively not triangles

    This is because of the Euler characteristic.

    I hope someone knowing Blender can answer more precisely to your question...
    Last edited: Jan 18, 2011
  6. TurtlesAreCool
    TurtlesAreCool New Member
    Magic said it better than I could have. What he said is absolutely correct for Blender. The faces count quads or triangles, depending on what you have in your model. Unless you have used the Ctrl+T command in edit mode on your model, it is probably in quads. Getting n-gons (>4 vertices) in Blender is tricky and is not something that will happen by accident.

    For example, let's say I start with the default cube. I have 8 vertices and 6 faces. Now, I go into edit mode, select all the vertices ('a' key), and triangulate (Ctrl+T). Now I have 8 vertices and 12 faces. So, the number does change depending on the type of polygons; as Magic says, Shapeways will always be counting triangles.
  7. Ray716
    Ray716 New Member
    Ahhh Thanks guys, much better info for me. Sometimes this stuff has a steep learning curve. But i have a few things in my shop, and i'm hoping to have a LOT more by the end of this year ;)

    Again, Thanks for the help! It is MUCH appreciated!