[vtkusers] Possibly found a bug in vtkImplicitModeller.cxx

[Roman Grothausmann]

Dear mailing list members,


Could it be that in vtkImplicitModeller.cxx there is a bug that causes 
the maximum distance (that is calculated and saved in the image) to be 
bigger than specified with SetMaximumDistance()?

 From the description of the filter and its parameters and also from the 
comments in the source I would expect that the output stored in 32-bit 
real does not contain values above SetMaximumDistance() except for the 
"background" value.

Having checked the source it seems to me that the squared distance was 
always very carefully assigned to a variable name ending with 2 (e.g. 
maxDistance2). However at line 967 there is a *= assignment (see patch 
below). Removing the '*', the output image of the filter then fulfils my 
expectations mentioned above.

Could the '*' be a bug?

--- VTK_orig/Hybrid/vtkImplicitModeller.cxx     2012-05-12 
13:59:27.000000000 +0200
+++ VTK/Hybrid/vtkImplicitModeller.cxx  2012-07-10 16:22:21.060066823 +0200
@@ -967,7 +967,7 @@
        }
      }

-  maxDist *= this->MaximumDistance;
+  maxDist = this->MaximumDistance;

    // Set volume origin and data spacing
    output->SetOrigin(this->ModelBounds[0],



Happy coding
Roman

-- 
Dr. Roman Grothausmann

Helmholtz-Zentrum Berlin für Materialien und Energie GmbH
Bereich Funktionale Materialien
Institut für angewandte Materialforschung
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