[vtkusers] Re: vtkThreshold Question

[Goodwin Lawlor]

Andrea Gavana wrote:
> Hello Goodwin,
>  
>     thank you very much for your help. It seems to me (if I have read 
> correctly the doc), that vtkExtractCells requires a vtkDataSet, a file 
> in other words... is that correct?

No, it requires an input dataset- any subclass of vtkDataSet. You could 
read the data from file using vtkXMLUnstructuredGridReader or create the 
vtkUnstructuredGrid yourself.

> Well, I already have a vtkUnstructuredGrid built by reading an external 
> file (not VTK format). The idea of extracting cells based on Ids 
> implemented in vtkExtractCells is very promising... there is nothing 
> similar but without using a vtkDataSet?
> The problem is, I should be able to filter out cells by certain 
> criteria: for example, at the moment I am trying to exclude inactive 
> cells using this ACTNUM, but I would like to be able to filter out the 
> cell based on, i.e., cell centroid depth, cell permeability, cell 
> saturations and so on. This seems to me something like a vtkFilter*, and 
> if every time I set up a new filter I have to create a file and re-read 
> it I will end up in doing slow things. 

Sounds like vtkThreshold is what you want here. Set the cell scalars to 
the values you calculate.

Goodwin