[vtkusers] vtkPolyDataNormals::ConsistencyOn problems

Tim Hutton T.Hutton at eastman.ucl.ac.uk
Thu Oct 24 07:06:49 EDT 2002

Hello vtkusers,

I have had occasional problems with vtkPolyDataNormals when consistency has 
been on and my surface is crumpled in places. I get streaks of reversed 
normals (appearing black) across the surface in places where there is no 
inconsistency, since the consistency is propagated out using a wave 
algorithm, in the order that the polygons are stored. I can get around the 
problem by simply turning ConsistencyOff().

Is there any need for a different normals algorithm that decides whether to 
enforce consistency based on some measure of how parallel the neighbouring 
polygons are? ie. if two neighbouring polys lie in the same plane then 
consistency is enforced more readily than if they make a sharp angle.

Apologies if this email makes no sense.


Tim Hutton,                        http://www.eastman.ucl.ac.uk/~dmi/MINORI
Research Fellow & PhD student,                   T.Hutton at eastman.ucl.ac.uk
MINORI Project, Biomedical Informatics Unit,     Tel: [+44] (0)20 7915 2344
Eastman Dental Institute, UCL,                   Fax: [+44] (0)20 7915 2303
256 Gray's Inn Road, London WC1X 8LD, UK      Mobile: [+44] (0)7748 678 832
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