[vtkusers] tags in VTK?

[Andy Bauer]

Hi Nico,

The more common way in VTK is just as you said -- to create a cell array
with that marking. That doesn't mean that you can't maintain a list of
cells in a subdomain. You could also work with pieces or a multiblock to
represent the subdomain.

The main issue though is how that data is supposed to be interpreted by
other things. If you're working on your own filters then you can have the
convention of a field data array to keep track of subdomains but most/all
VTK filters will have no idea what that data represents. The idea here is
that if you want to a threshold filter to keep only certain subdomains you
can either use a cell data array and the vtkThreshold filter or your own
convention and your own threshold filter.

Cheers,
Andy


On Sat, Mar 11, 2017 at 1:39 PM, Nico Schlömer <nico.schloemer at gmail.com>
wrote:

> Hi everyone,
>
> To mark subdomains in VTK, I guess the most common thing is to use a
> integer-valued cell (or point) function that associates every cell with a
> subdomain index. Is this correct or are there other ways for marking
> subdomains?
>
> In other mesh formats, I've seen the approach of tagging entities, i.e.,
> subdomain X would be represented by a list indices into the cell (or point)
> array. This fits many of my applications better since I typically need to
> iterate over all cells of a subdomain. The function approach makes it hard
> to even find out how many subdomains there are, let alone to have one cell
> belong to two subdomains at once.
>
> Any hints here?
>
> Cheers,
> Nico
>
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