[vtkusers] Problems using implicitfunctions

[laurent.paul at club-internet.fr]

Hi all, 
   
  I'm a bit lost ... 
  I want to clip a PolyData using a SuperQuadric. For that purpose, I have  created a SuperQuadricSource, I display it on the screen, move it,  validate its positionning and clip the polydata. 
   
  First, I can't use the SuperQuadricSource to create a SuperQuadric  ImplicitFunction. I thought it would be easy but there is no possible  conversion (or hadn't found it). So, I have found 2 possibilities: 
      1) Recreate a SuperQuadric ImplicitFunction using the properties of  the source. 
      2) Create an ImplicitDataSet from the SuperQuadricSource 
   
  My problems: 
  1) I have to transform the SuperQuadric ImplicitFunction using the  SetTransform method provided in the ImplicitFunction class. I use the  same transform than the one that transforms the SuperQuadricSource but  the result is not correct. I have tried a lot of combinations  (preTranslate to the origin, rotate and postTranstlate, Set the center  manually...) but I have never managed to obtain the correct orientation  for the SuperQuadricImplicitFunction. 
  2) It is not so easy... I found in the mailing list that I have to  triangulate the transformed SuperQuadricSource using a Delaunay3D,  create elevation filter to generate a scalar value for cells (don't  really understand why....), set the result as ImplicitDataSet. This  solution works but is very slowly. 
  A problem with that solution is that I get only the entire cells that  lie inside the ImplicitDataSet. How can I get the clipped cells on the  border of the implicitDataSet? Does this behavior happen only when using  ImplicitDataSet? I have never seen that using a clipping plane. 
   
  Last question: My original PolyData seems to be bad quality. It has been  producted using vtkMarchingCubes, SmoothPolyData followed by  DecimatePro. Do I have to remesh using a triangleFilter or a Delaunay3D? 
   
  Many thanks for your reply. 
  Laurent. 
   

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