[vtkusers] Removing and replacing a set of cells

[Goodwin Lawlor]

Hi Justin,

I've faced the same problem a (long) while ago. Have a look at the
vtkCellsFilter and vtkRemoveCellsFilter (its subclass) here:
https://github.com/glawlor/vtkbioeng

hth

Goodwin


On Sat, Feb 1, 2014 at 3:25 PM, eldridgejm <eldridgejm at gmail.com> wrote:

> I am using VTK to visualize a surface. When the user triggers an event, I'd
> like to remove a connected part of the surface and replace it. To make
> things clear, I've made some (admittedly poor) drawings of a very simple
> example:
>
> Suppose my polyData consists of the following 10 points as viewed from
> above: http://imgur.com/U4uTUOQ
>
> Initially, my surface looks like this: http://imgur.com/xhQYqKs
> All points are included, except for point 9.
>
> Upon the user triggering an event, I would like to redraw the surface so
> that it looks like this: http://imgur.com/rzzPPTK
> That is, the topology is changed to include point 9, but not point 8.
>
> When the selection is made, I know precisely which triangles to delete from
> the polyData: (4,5,8), (5,6,8), (6,7,8), and (7,4,8). I can delete these
> with DeleteCells, then update the polyData to reflect the new topology by
> inserting the triangles: (4,5,9), (5,6,9), (6,7,9), and (7,4,9).
>
> This method has a problem, however: DeleteCells requires that I specify the
> Ids of the cells I'd like to delete. When I construct the surface, I keep
> track of the ids of the triangles I create so that when the user triggers
> the action, I know exactly which ids correspond to the triangles that need
> to be deleted. After deleting cells, however, these ids will be stale. This
> is an issue if the user would like to trigger the event on multiple parts
> of
> the surface: the first event will be handled correctly, but upon triggering
> the second event, I do not have a valid listing of the cells which I should
> delete. Updating the ids after the first deletion would appear to be both
> tedious and computationally inefficient.
>
> The alternative, it seems, is to completely clear the polyData's polygons
> and insert all of the polygons again, which requires no reference to the
> cell ids. This method strikes me as inefficient as well, and I think that
> there is likely a better way. What would be the natural way to accomplish
> this?
>
>
>
> --
> View this message in context:
> http://vtk.1045678.n5.nabble.com/Removing-and-replacing-a-set-of-cells-tp5725743.html
> Sent from the VTK - Users mailing list archive at Nabble.com.
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