Continuous Topology

Discussion in 'Technologies and Hardware' started by Jason_Nuttall, Mar 6, 2013.

  1. Jason_Nuttall
    Jason_Nuttall New Member
    Hi all,
    I was about to start my first 3D printing project and can't find any information on this.
    Do models need one continuous piece of topology or can they be a combination of models created together.

    For example if I have a cube with a cube sat on top, would the top cube have to be extruded from the bottom one or could it be another seperate cube just placed on top?


  2. stonysmith
    stonysmith Well-Known Member Moderator
    Yes, you can have separate shells, but.. be careful. There are a couple of things that will cause you trouble.
    1) There is a topic called "non-manifold" that you need to study up on. There's a couple of tutorials here that address it. Basically, your model must not have co-incident corners or faces because the software systems get confused by it. If they overlap by even a microscopic amount, then it's fine, but if they are perfectly parallel, it causes confusion. As you suggest, it's slightly better to extrude from one face, but there is another choice. Setup the two cubes, have them overlap slightly (even by .000001) and then us a "boolean operator" to merge the two shells together.

    2) If do have separate elements, and if one of the cubes is below a certain size, it may get "weeded out" during the cleanup software that Shapeways uses. Things below 0.1mm tend to get lost if they are separate shells.

    One option you have (if your model is a STL file) is to upload your model to which will union all your shells together into a single surface.