CGAL users discussion list

[toddoe <>]

Hi All,
First thanks for all the help in the past. I now have a well-working
compiled solution (cgal 3.6.x).

Here is a major issue that I have attempted to 'work-around' but cannot
succeed.

I am trying to mesh a simple 'embedded' cylinder where the inner cylinder is
in 'contact' with the outer 'ring'. and the whole thing is capped at the
ends. (see links to pics later).

unfortunately, there are serious problems. at the intersection of the 'caps'
the inner/outer cylinder tetrahedron are very jagged. :(

see these images (generated using matlab):
cylinder 'side on': http://biomeq.com/meshpicstemp/sideon.png
cylinder 'oblique': http://biomeq.com/meshpicstemp/oblique.png
without end caps: http://biomeq.com/meshpicstemp/withoutcapoblique.png
top view annotated/problems:
http://biomeq.com/meshpicstemp/topviewannotated.jpg

the 'frownyface' shows where the mesh is 'spiking' into the adjacent
domain... this disables ANY contact algorithm, since some elements are
'spiking' or protruding into adjacent mesh domain... a very big problem.

i have tried a wide range of parameter values and even with extreme
refinement always have the same problem.

i realize that this artifact is likely due to the lack of 'edge preserving'
in the current 3D mesh implementation.

BUT: does anyone have any ideas or workarounds for this issue?? I cannot
generate any FEA contact problem given this unfortunate spiking. I have
tried all kinds of mesh-parameter variations and to no avail. It just
produces smaller spikes.

Also, if the "edge-preserving" issue is the main problem, is there any
time-line for solving this? I've noticed that this was proposed for CGAL 3.7
but would like to inquire if this is really on the books.

I ask with great interest because we have a large potential for grants, etc.
here at Drexel University but with this artifact we cannot create contact
meshes... thus, we cannot create the meshes for preliminary data. it's
crippling. 

We can write grants with funds to support CGAL, but we need to have some
idea of how to solve this problem and a timeline.

thanks very much in advance for any info.
best,
todd




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