Cross-disciplinary confusion

So this is my first month or so doing 3D printing. I’m not an engineer and I’ve never touched AutoCAD.

My background is in video games; I’ve been doing 3D art in Maya day in and day out since the turn of the century.
Modeling for video games has always been about optimization. Every polygon has to contribute to the shape of the mesh. No duplicate vertices, no stray edges. And above all, keep your triangle count as low as possible.

That’s changed somewhat since my days of making 100-poly models for DreamCast hardware. And get off my lawn, you kids with your normal mapping and 30K triangle characters and your ZBrush.

One thing I’ve discovered is that when it comes to this particular kind of 3D printing, it’s OK to be a little loosey-goosey. I don’t have to join every vertex to a neighbor, I can have a few stray edges here and there. A model isn’t going to explode during a render because I didn’t weld the arm to the body properly.

Take a look at the original 4-hole gear model for Etchasketchulator. I spent way too much time painstakingly welding verts, especially in the holes for the grub screws. The gear teeth are connected to the top and the bottom faces of the gear. Everything is watertight– you could throw this model (tessellated) into an N64 and it would render, albeit at 3FPS.

By the time I got around to making a second, thicker version of the gear, I’d learned a lot. The gear teeth are just kind of close to the gear faces– no welding.  I used a Boolean operation to cut the holes in the sides of the gear shaft.

A Boolean is a modeling tool that uses brute force calculation to add, subtract, or intersect two pieces of geometry.

Old-school video game modelers may suppress a shudder at the use of a Boolean. They generally create way more geometry in the wrong places than they’re worth, at least in realtime rendering.

In 3D printing, I can be sloppy. It’s very liberating.

2 thoughts on “Cross-disciplinary confusion

  1. Andyways

    I’ve been wondering who else out there is using maya for makerbot modeling/printing. Just for clarification, the top plane of the gear is not connected to the teeth? I thought this violated the whole “manifold” requirement. If this is not the case, I have been wasting a lot of time in maya getting my geometry print ready.

    1. zheng3

      That’s right, with this gear model very little is actually connected. Watertight models aren’t critical for printing with A makerbot ReplicatorG, although they might slice strangely.

      In general, manifold models are better, especially if you’re printing with a service like Shapeways or Ponoko, where they’re required. This was one of my first printed models, and I’ve learned a lot since then. You can get away with a lot of cutting corners on a MakerBot at home though.

      If I had to do this model again, I’d use the boolean tools more frequently. Boolean the gear to the collar, no muss, no fuss. My experience has been that polycount isn’t as important when I’m 3d printing, and as long as everything’s triangulated you’re good.


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