Reversed faces
I don't think detecting and highlighting reversed polyhedra faces has any
connection to tangential problems with cylinder does it?
Basically you need to avoid a tangential interfaces because even with a
perfect mathematical curve you create an infinitely thin knife edge that is
problematical.
Keeping $fn a multiple of 4 is a good idea and using hull instead of union
if possible. Now that 2D uses fixed point things get even more tricky.
On 12 January 2016 at 12:06, MichaelAtOz oz.at.michael@gmail.com wrote:
Many of my issues occur with lines/planes and faces of circles/cylinders
with
varying $fn values, particularly intersection/difference, how does this
approach consider the tangential inconsistency of the curve approximation.
He says naively... ;) or provocatively...if I have 1/2 an understanding...
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kintel wrote
Some related issues:
https://github.com/openscad/openscad/issues/348
https://github.com/openscad/openscad/issues/1042
https://github.com/openscad/openscad/issues/590
Two things:
o We should rewrite our mesh class to support tests and operators like
this. This would also be a good step towards repairing imported STLs which
CGAL struggles with. We could also look at external libraries with good
mesh classes.
o Highlights of reversed faces in preview mode: It should be possible to
simply turn this on.
-Marius
Hi Marius,
Has anyone (re)visited the "Polygon Mesh Processing" features available in
latest CGAL?
http://doc.cgal.org/latest/Polygon_mesh_processing/index.html
There seem to be quite a few Useful Features built in now related to hole
filling, and related mesh repair and manifold-ness.
Andrew.
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On Jan 15, 2016, at 12:24 PM, clothbot andrew@plumb.org wrote:
Has anyone (re)visited the "Polygon Mesh Processing" features available in
latest CGAL?
I haven’t looked into it yet. CGAL APIs scare me : /
-Marius
I decided to prod “mesh processing" a bit with a pointset primitive stick. Nothing formal commit-able to the master tree yet, but it “does stuff that is (mostly) manifold."
https://github.com/clothbot/openscad/tree/read_issue1324 https://github.com/clothbot/openscad/tree/read_issue1324
On Jan 15, 2016, at 1:15 PM, Marius Kintel marius@kintel.net wrote:
On Jan 15, 2016, at 12:24 PM, clothbot andrew@plumb.org wrote:
Has anyone (re)visited the "Polygon Mesh Processing" features available in
latest CGAL?
I haven’t looked into it yet. CGAL APIs scare me : /
-Marius
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On Jan 18, 2016, at 20:49 PM, Andrew Plumb andrew@plumb.org wrote:
I decided to prod “mesh processing" a bit with a pointset primitive stick. Nothing formal commit-able to the master tree yet, but it “does stuff that is (mostly) manifold.”
Nice.
Btw., what’s the main difference between this, and doing a convex hull over the points?
Would this be used to e.g. tessellate a 3D scan point cloud?
-Marius
kintel wrote
On Jan 18, 2016, at 20:49 PM, Andrew Plumb <
andrew@
> wrote:
I decided to prod “mesh processing" a bit with a pointset primitive
stick. Nothing formal commit-able to the master tree yet, but it “does
stuff that is (mostly) manifold.”
Nice.
Btw., what’s the main difference between this, and doing a convex hull
over the points?
Would this be used to e.g. tessellate a 3D scan point cloud?
-Marius
The convex examples are just me picking my battles. Yes, I used the surface
reconstruction from point sets code as a starting point:
...to get a feel for how all the different parameters interact. I used the
POLYHEDRON primitive pieces as a starting-point for the code.
Next-up: pair it with a "read_xyz()" function to read in .xyz scannner
pointset files and see how far I get.
Andrew.
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Mwahahaha! Function read_xyz() added.
https://github.com/clothbot/openscad/tree/read_issue1324
https://github.com/clothbot/ClothBotCreations/blob/master/examples/test_read_xyz.scad
https://github.com/clothbot/ClothBotCreations/blob/master/examples/oni.xyz
Aside: The error is expected because of the read_xyz("invalid.xyz") call.
http://forum.openscad.org/file/n15777/test_xyz_screenshot.png
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