neobobkrause wrote:@dorsai3d: I'd again challenge your personal distaste for non-manifold surfaces. You call them 'ugly hacks.' But are you aware that S3D already supports them in a number of ways? I suspect you aren't aware of this support because it isn't evident to those who never import non-manifolds. Vases are just one common example of a shape that's inherently non-manifold. Are you equally offended by today's Vase Mode? The only difference between manifold and non-manifold shapes is that closed shapes can be infilled. Perhaps it's the case that the design tools that you're familiar with don't support surfaces as first-class object types.
I'd appreciate it if you didn't assume that I don't know about the subject - I've been working with 3D modeling and CAD software for more than 10 years, and have a pretty solid understanding of how models (real surfaces, tessellated surfaces, and solids) work.
neobobkrause wrote:I can see that they're treating all shapes processed in that mode as non-manifold.
Uh...no... They're treating them as single perimeter, 0 infill solids that you can spiralize the perimeters on. In cases where you can't spiralize the perimeters, like when the model has multiple islands, the software switches back to standard layers.
I'm of the opinion (and I'm pretty sure I'm not the only one) that you should model what you want to get. You can make a manifold model of a vase, and that should print well. The thing is that a model that you want to print should have volume, since what you're printing has volume. Surface entities have no volume, but if you add a thickness to it, you can get exactly what you want.
The problem is that currently in Simplify3D, if you have a thin wall (lets define this as less than two extrusion widths), there's two ways it gets handled, both of which I think are unsatisfactory.
1) The wall is thinner than one extrusion width and does not get printed at all
2) The wall is thicker than one extrusion width (this includes by 0.01mm) but thinner than two extrusion widths. This wall gets two full width extrusions overlapping one another, resulting in messy overextrusion
neobobkrause wrote:Polygons in a mesh have a 'normal vector.' That is, they face in a particular direction that defines which side is inside and which is outside. Slicers basically have 2 jobs: A) generate gcode for the outward face of a mesh, and B) infill the inside of a volume. In order to have volume, manifold shapes must include a mesh with a normal facing in a particular direction -- and another mesh facing in the opposite direction. If either are missing then the shape isn't manifold.
You're thinking too much like graphics and not enough like solids. STL is a terrible file format because it allows you to define all sorts of invalid geometry, and slicing engines have to support non-manifold geometry because of certain limitations of the format, and the fact that when slicing, it's hard to distinguish between a surface that's only there as a simple surface, and one that's part of a solid body.
The goal when printing is to create a solid object that (as closely as practical) follows the solid object described by the computer model, not to create perimeters for every face described by the horrifyingly outdated file format that we're stuck with for legacy reasons. So the faces of the model define the volume, and the slicer should be able to work out how to fill that volume appropriately, including measures like single perimeters.
neobobkrause wrote:Would you suggest that the slicer print one of the faces but not the other? Now that would be an ugly hack.
A single line that is the thickness of the wall would inherently print both faces of that wall (technically all 4), so your snide last comment isn't very valid anyways...
We both want the same end goal, but you're describing a method of getting there truly is a hack - using zero volume objects to trick the slicer into generating a prescribed volume (*) that it isn't able to create properly otherwise.
(*) A poorly prescribed volume, as well, since instead of describing your wall thickness in the model (the supposed specification of the end part you want!) you're relying on the extrusion width that you've selected in your slicing profile to define the wall thickness. If you want a 0.4mm wall, don't you think you should be able to model a 0.4mm wall and get that regardless of whether you're printing with a 0.35mm nozzle or a 0.1mm laser (or one of the million other methods to make a computer model real)?