Self-intersecting meshes

Discussion in 'Design and Modeling' started by Laserschwert, May 7, 2009.

  1. Laserschwert
    Laserschwert New Member
    Hey there,

    I have a major problem regarding the usage of rigged 3D-characters out of 3dsmax with Shapeways. Since posing them results in partially self-intersecting meshes, I can't upload the files to the site, as the meshes seem to be regarded as having "inverted normals".

    Self-intersection occurs for example when the character's arm is held close to its body, so that a part of the arm or the elbow dips into the torso, or usually in "tight" areas, like the armpit. This isn't a problem when rendering, but obviously it isn't accepted by Shapeways. Now, how do I pose characters, without self-intersections? The only solution would be to "boolean" the mesh with itself, thus creating one solid object. Unfortunately, to my knowledge there's no tool in 3dsmax to perform a "self-boolean" like this.

    Any ideas?
  2. Hello,

    Just thought I'd let you know that Shapeways printing does allow intersecting objects, provided both of the objects are watertight and manifold. (Test this for yourself if you doubt me - make two cubes, then place them so they overlap). It also allows one complete object inside another, in which case the internal object becomes an empty volume or hollow. (Use this to make a hollow cube).
    This being the case, your object should still print, even if it is self-intersecting. This suggests to me that your problem is either with the export process, or the original mesh. (The 'inverted normals' warning suggests that either part or all of the mesh is 'inside out' with the normals facing inward.) To determine the exact issue, make a cube or two as above, and test whether you can upload the results. Then make a cylinder or long rectangle, and bend it back so it intersects itself. Based on what does or does not upload you should be able to determine where exactly you have gone wrong.
  3. Laserschwert
    Laserschwert New Member
    Looks like I wasn't clear enough:

    I don't have any problems with separate objects intersecting, but with A SINGLE MESH intersecting with itself (like the sleeve of a jacket intersecting with another piece of the jacket). Hence: SELF-intersection. Having just two separate objects overlap was never a problem. So your "long cylinder" test is basically what I have... only more complex.
  4. bartv
    bartv New Member
    I ran a few tests with self-intersecting meshes and found no problems with them - you'll find an example in the attachment to this post.

    Maybe there's another issue with your model. Feel free to mail it to and I'll look in to it for you.



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