[vtkusers] Re: Fill contours with Pixels

[Goodwin Lawlor]

Mike Jackson wrote:
> I tried again, but I still get these errors:
> 
> 
> Warning: In /Users/Shared/OpenSource/VTK-5.0.2/Filtering/vtkPolygon.cxx, 
> line 562
> vtkPolygon (0xb300910): Degenerate polygon encountered during triangulation
> 
> which means there is something wrong with my Mesh? I am including an 
> image of my Mesh with the areas that need to be filled in outlined in 
> Blue. This was Done with ParaView. Note that some of the "holes" 
> traverse different planes, and some "holes" have more "holes" within them.
> 
> 
> ------------------------------------------------------------------------

Hi Mike,

If your surface mesh is the output of a contouring operation on a 
volume, the you may be able to circumvent triangulating the boundary 
loops by padding the volume by one voxel in each direction with the 
background value (another poster suggested just this...). This is the 
best and easiest way.

If you don't have the original volume and can only triangulate, here are 
a couple of things that could be going wrong:

1. vtkStripper is hitting its "MaximumLength" ... just increase this var.

2. Sometimes vtkStripper will output two or more polylines from a 
connected series of input lines, instead of just one. This is a bug, see 
here: http://www.vtk.org/Bug/bug.php?op=show&bugid=832

3. Maybe vtkTriangleFilter isn't up for the job (not sure it works on 
concave polygons). You could try vtkDelaunay2D or try to resurrect 
vtkGLUTesselatorTriangleFilter - see here:
http://public.kitware.com/pipermail/vtkusers/2005-August/081302.html
http://public.kitware.com/cgi-bin/viewcvs.cgi/Hybrid/Attic/vtkGLUTesselatorTriangleFilter.cxx?view=markup

4. If all else fails, you could try using the boundary loops to clip a 
planar grid (that would have been the boundary of the volume) with 
vtkSelectPolyData. vtkSelectPolyData expects a loop without coincident 
first and last points so you can't feed it the boundary loops 
directly... I can send you some c++ code I have to deal with this.

hth

Goodwin