Re: Triangle call unsuccessful

["irishmist_ <djtim@xxxxxxxxxxxxxxxx>" <djtim@xxxxxxxxxxxxxxxx>]

Dave,

Thanks for detailed explanation. Now I fully understand what is 
going on with the import considering the geometry I have why the 
tighter tolerance would cause meshing failure. I was thinking the 
tolerance was more for precision not gap closing.

Dan


--- In femm@xxxxxxxxxxxxxxx, "David Meeker <dmeeker@xxxx>" 
<dmeeker@xxxx> wrote:
> --- In femm@xxxxxxxxxxxxxxx, "irishmist_ <djtim@xxxx>" <djtim@xxxx> 
wrote:
> > Thanks for the comment Jiri. However, I think you missed my 
point. 
> > I am very aware of the angle issue Dave has mentioned. Here is 
the 
> > scenario... I am doing a DXF import... the tolerance dialog box 
> > comes up on the screen and I change it to some number, say E-10 
and 
> > then try and run the mesher. I get the "Triangle can't run" 
message.
> > 
> > Take same DXF file and import leaving the tolerance at the 
default 
> > value. Triangle runs without a problem. 
> > 
> > Identical geometry on import... one meshes --- one doesn't -- all 
> > because of the tolerance setting during the file import.
> > 
> > Dan
> 
> I think that this is a case of things being ambiguous because of not
> being very well documented. A problem with DXF files is that there
> often isn't enough precision to ensure that points that coincide
> actually do, etc. What the "tolerance" box represents is the 
maximum
> distance between two points at which the DXF import routine 
considers
> that two points should actually coincide.
> 
> The program picks some tolerance that ought to be "good enough", 
based
> on the total dimensions of the problem. However, there can still
> sometimes be problems. If there are problems, you actually want to
> make the tolerance _larger_ so that that there is less chance of the
> program missing two points which ought to actually coincide. You
> generally don't want to make the tolerance smaller.
> 
> Even if a geometry does mesh successfully after DXF import, it is
> important to check things to make sure that they are consistent --
> e.g. no small gaps that cause a region which should be closed not to
> be closed. If you look at the mesh generated, problem areas usually
> concide with intersections where Triangle has placed an extremely 
high
> density of triangles.
> 
> One more note--whenever you export a DXF file from a CAD program, 
make
> sure to do it using the highest possible precision settings.
> 
> Dave.