[vtk-developers] Bugs in vtkWedge

[Francois Bertel]

the piece of you mentioned -> the piece of code you mentioned

Francois Bertel wrote:
> Hi Tadeu,
> 
> The description of the vtkWedge class says:
> 
> "(0,1,2) is the base of the wedge which, using the right hand rule, forms a triangle whose normal points outward (away from the triangular face (3,4,5)"
> 
> I agree it is different from other cells but the description itself match the implementation. so GetFaceArray() is fine.
> Also  in the VTK text book, normal of 0-1-2  points toward the exterior and normal of 3-4-5 points toward face 0-1-2, so the face such that the normal points
> toward the exterior is 3-5-4.
> 
> The example you gave, according to this description is wrong because obviously the normal of the first face you defined points toward the other face.
> 
> Try thoses points instead:
> 
> (8,0,8), (16,0,8), (16,8,8) (8,0,0), (16,0,0), (16,8,0)
> 
> and tells us if EvaluatePosition() stills return true.
> 
> I'm talking about VTK CVS.
> Which version of VTK are you talking about? I don't see the piece of you mentioned in EvaluatePosition() in VTK CVS.
> 
> Regards.
> 
> Tadeu Manoel wrote:
> 
>>There is a bug in vtkWedge::EvaluatePosition, it can tell a point is
>>inside when in reality it is outside.
>>
>>E.g, try to create a vtkWedge with the following points:
>>(8,0,0), (16,0,0), (16,8,0), (8,0,8), (16,0,8), (16,8,8)
>>
>>And try to EvaluatePosition for point (17,6,4). It will return 1,
>>telling it is inside.
>>
>>A solution is to change the following code:
>>
>>  if ( pcoords[0] >= -0.001 && pcoords[0] <= 1.001 &&
>>  pcoords[1] >= -0.001 && pcoords[1] <= 1.001 &&
>>  pcoords[2] >= -0.001 && pcoords[2] <= 1.001 )
>>
>>To:
>>
>>   if ( pcoords[0] >= -0.001 && pcoords[1] >= -0.001 &&
>>       (pcoords[0] + pcoords[1]) <= 1.001 &&
>>        pcoords[2] >= -0.001 && pcoords[2] <= 1.001 )
>>
>>
>>
>>There is another bug in its faces array (and with GetFace and GetFaceArray):
>>The faces normals are pointing inside, instead of outside (as of all
>>other 3D cells).
>>Instead of:
>>
>>static int faces[5][4] = { {0,1,2,-1}, {3,5,4,-1},
>>                           {0,3,4,1}, {1,4,5,2}, {2,5,3,0} };
>>
>>It should be:
>>
>>static int faces[5][4] = { {0,2,1,-1}, {3,4,5,-1},
>>                           {0,1,4,3}, {1,2,5,4}, {2,0,3,5} };
>>
>>
>>
>>--
>>Edson Tadeu M. Manoel
>>ESSS - Engineering Simulation and Scientific Software
>>http://www.esss.com.br
>>
>>
>>
>>
>>------------------------------------------------------------------------
>>
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> 
> 
> 


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François Bertel, PhD  | Kitware Inc. Suite 204
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