[vtk-developers] BUG - vtkappendpolydata

[clinton at elemtech.com]

I've seen it too in ParaView.
http://public.kitware.com/Bug/view.php?id=5899
No one has claimed that bug yet.

Clint

On Friday 11 January 2008 2:10:22 pm Vinny BigD wrote:
> Hi,
>
> I not sure if its the right place to submit an abnormal behavior...
>
> The problem seems to be with vtkAppendPolyData.  I'll try to be clear as 
> possible.
>
> Here is the case:
>
> I manually build 2 vtkPolyData each containing 1 polygon(sqares) (1  cell)
> with one scalar attribute.
>
> Then I use 2 vtkLinearExtrusionFilter to extrude those 2 vtkPolyData at  2
> different heights.
>
> Then, I add them to the vtkAppendPolyData and pass the result to the 
> mapper wich use the scalar data for color mapping.
>
> PROBLEM:
>
> Everything seems ok, EXCEPT that the 2 colors are randomly distributed  on
> each faces of the cubes( we expect that each cube is uniformly colored).
>
> After long debugging sessions, it seems that the  vtkLinearExtrusionFilter
> generate cells of type TriangleStrips AND  Polygons.  The vtkAppendPolyData
>  then seems to copy polygonal data of  each polygon and THEN copy the
> strips data. Result : the association  between cell and scalar data is
> corrupted. (See example below)
>
> What I did to resolve the problem: I added a vtkTriangleFilter before 
> adding to vtkAppendPolyData.  This way all cells are of type Strips and 
> the association/ordering of scalar data is correct and the display ok.
>
> That behavior is not normal...I guess it should work without this 
> additionnal filter.
>
> thanks,
> ***
> EXAMPLE:
> Cells list (vtkAppendPolyData->GetOutPut()) AFTER ADDING 1st POLYGON
> CELL: Id, (List of pointsId), scalar value
> CELL : 0 (4,1,3,) Scal: 0
> CELL : 1 (9,6,8,) Scal: 0
> CELL : 2 (2,3,1,) Scal: 0
> CELL : 3 (7,8,6,) Scal: 0
> CELL : 4 (4,1,9,6,) Scal: 0
> CELL : 5 (3,4,8,9,) Scal: 0
> CELL : 6 (2,3,7,8,) Scal: 0
> CELL : 7 (1,2,6,7,) Scal: 0
>
>  Cells list (vtkAppendPolyData->GetOutPut()) AFTER ADDING 2nd POLYGON  -
> The ordering is incorrect CELL : 0 (4,1,3,) Scal: 0
> CELL : 1 (9,6,8,) Scal: 0
> CELL : 2 (2,3,1,) Scal: 0
> CELL : 3 (7,8,6,) Scal: 0
> CELL : 4 (14,11,13,) Scal: 0
> CELL : 5 (19,16,18,) Scal: 0
> CELL : 6 (12,13,11,) Scal: 0
> CELL : 7 (17,18,16,) Scal: 0
> CELL : 8 (4,1,9,6,) Scal: 1
> CELL : 9 (3,4,8,9,) Scal: 1
> CELL : 10 (2,3,7,8,) Scal: 1
> CELL : 11 (1,2,6,7,) Scal: 1
> CELL : 12 (14,11,19,16,) Scal: 1
> CELL : 13 (13,14,18,19,) Scal: 1
> CELL : 14 (12,13,17,18,) Scal: 1
> CELL : 15 (11,12,16,17,) Scal: 1
>
>
> ---------------------------------
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