[vtk-developers] contour lines and scalar color plot issues with vtkUnstructuredGrid

[Wylie, Brian]

You can run 'CleanToGrid'. That filter will merge co-incident points,
this may solve your problem... worth a try at least :)
 

Brian Wylie - Org 9227 
Sandia National Laboratories 
MS 0822 - Building 880/A1-J 
(505)844-2238 FAX(505)845-0833                       
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________________________________

	From: vtk-developers-bounces+bnwylie=sandia.gov at vtk.org
[mailto:vtk-developers-bounces+bnwylie=sandia.gov at vtk.org] On Behalf Of
Randall Hand
	Sent: Wednesday, February 15, 2006 8:59 AM
	To: Burlen
	Cc: John Dorelli; vtk-developers at vtk.org;
Douglas.Larson at unh.edu; vtkusers at vtk.org; Jimmy Raeder; Thompson, David
C
	Subject: Re: [vtk-developers] contour lines and scalar color
plot issues with vtkUnstructuredGrid
	
	


	On 2/15/06, Burlen <burlen at apollo.sr.unh.edu> wrote: 


		It seems to me that the problem of open contours might
be caused by the
		algorithm(s) used with unstructuredGrids built with the
append filter. Could
		it have somehting to do with the fact that the boxes in
my case are appended 
		in a "willy nilly" order? adjacent boxes aren't
necessarily appended one
		after the other.
		
		


	I think this is the cause of your problem.  The vtkAppendFilter
does not "stitch" neighboring datasets along their boundaries, it keeps
each dataset as an individual piece.  So when you extract an isosurface
from the combined dataset, there is no connectivity along those
inter-dataset boundaries, leading to the "discontinuity" along the
edges.  I've run into the same issue here doing similiar things (reading
a multi-block Plot3d file & using AppendDataset to only have 1
vtkDataSet to pass around). 
	
	How to fix this?  I haven't the slightest, short of writing
custom code to replace vtkAppendDataset and do the stitching.  You may
be able to Resample the Data into a rectilinear form (use the
ProbeFilter with an ImageData input), and then get the Isosurface you
want, but you'll have to live with the resolution tradeoffs.  It'll also
be sloooooow.... 
	
	
	-- 
	Randall Hand
	Visualization Scientist, 
	ERDC-MSRC Vicksburg, MS
	Homepage: http://www.yeraze.com 

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