3D Mesh Design Rules

Have questions or comments about Simplify3D, Slic3r, Cura, Reptier, etc? Or wondering about which CAD software to use...discuss it here...
jsc
Posts: 1864
Joined: Thu Apr 10, 2014 4:00 am

Re: 3D Mesh Design Rules

Post by jsc » Sat Mar 19, 2016 7:57 pm

It's fairly easy to get situations that OpenSCAD should be able to resolve, but doesn't. Difference two concentric cylinders of different diameters and the same length, and you will get that z-fighting plane glitch on the ends. I see models like this on Thingiverse all the time. They seem to print well enough, but I don't like models that flicker.

ajmadison
Posts: 42
Joined: Tue Aug 11, 2015 2:13 am

Re: 3D Mesh Design Rules

Post by ajmadison » Mon Mar 21, 2016 11:34 pm

ednisley wrote: If you have an "real" 3D modeling program that manipulates 3D solids, rather than a mesh-modeling program that drapes meshes around the shape of objects (to produce lush "3D" renderings), you'll almost certainly get better results by remaining with the 3D solids as long as you possibly can. Performing CSG (Constructive Solid Geometry) operations on solids generally produces manifold results, as long as you avoid the gotchas on the list I gave earlier.

The hardest lesson to learn is to not build objects by butting blocks up against each other: they must overlap very slightly to make the common faces non-coincident (they don't meet in a common plane). Better still, subtract blocks from a larger one to ensure the result remains a single solid object.

That's tedious, but seems (to me, anyhow) less annoying than repairing mesh errors ...
Excellent advice. Yes, I've learned my (first?!) lesson. Stay with the solid modeling, and make copies of the file when converting over to a mesh, prior to exporting to the STL. So I can back up to the Solids, figure out what the issue is, correct it, and try again. And you've confirmed what I suspected, I should deliberately overlap, rather than butt objects (solids) up against each other. That's where I had my most trouble. Thanks.

For the record, I'm using Rhino. McNeel was running a special for the Mac version last year, and I "jumped on it." Particularly happy with the immediate documentation that shows up when I select a command.

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