[vtk-developers] Bugs in vtkWedge

[Francois Bertel]

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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François Bertel, PhD  | Kitware Inc. Suite 204
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