[vtkusers] Problem with surface reconstruction and contour filter in C++.

[Andrew J. P. Maclean]

I found the problem! It has to do with Update(). If you do
surf->Update(); immediately after surf->SetInput() contouring doesn't
work.

So the following code works OK. 

		polyData->Modified();
		surf->SetInput( polyData );

		// Contour at 0 to extract the surface.
		vtkContourFilter * cf = vtkContourFilter::New();
		cf->SetInput( surf->GetOutput() );
		cf->SetValue(0,0.0);

		// Sometimes the contouring algorithm can create a
volume whose gradient
		// vector and ordering of polygon (using the right hand
rule) are 
		// inconsistent. vtkReverseSense cures this problem.	
		vtkReverseSense * rev = vtkReverseSense::New();
		rev->SetInput(cf->GetOutput());
		rev->ReverseCellsOn();
		rev->ReverseNormalsOn();
		rev->Update();

		//polyData->Reset();
		polyData->Initialize();
		polyData->DeepCopy(rev->GetOutput());Andrew

___________________________________________
Andrew J. P. Maclean
Postal:
Australian Centre for Field Robotics
The Rose Street Building J04
The University of Sydney  2006  NSW
AUSTRALIA
 
Room:  106
Phone: +61 2 9351 3283
Fax:   +61 2 9351 7474
       http://www.acfr.usyd.edu.au/

___________________________________________


-----Original Message-----
From: John Biddiscombe [mailto:jbiddiscombe at skippingmouse.co.uk] 
Sent: Tuesday, 15 October 2002 10:29
To: a.maclean at acfr.usyd.edu.au; vtkusers at public.kitware.com
Subject: Re: [vtkusers] Problem with surface reconstruction and contour
filter in C++.

> However it still doesn't fix my problem, in that the contour filter is
> not returning any data.

Oh. Sorry, I only looked at the compile error. My first guess would be

  // Description:
  // If you want to contour by an arbitrary array, then set its name
here.
  // By default this in NULL and the filter will use the active scalar
array.
  vtkGetStringMacro(InputScalarsSelection);
  void SelectInputScalars(const char *fieldName)
    {this->SetInputScalarsSelection(fieldName);}

Try setting the scalar name to something appropriate and see if that
helps.
Could be somehow you're getting a different scalar name in your data
somehow
(and the contour filter isn't using it).

JB