[vtkusers] vtkCellArray - efficient use

[Paul Harris]

Hi,

I have the following code:

vtkCellArray * p_cells = vtkCellArray::New();

p_cells->Allocate( ids.size() );

for ( vector<vtkIdType>::const_iterator id = ids.begin(), id_end =
ids.end(); id != id_end; ++id )
   p_cells->InsertNextCell(1,&*c);


But, I am not sure that my Allocate() call is correct.  Should it be:
Allocate(ids.size()*2);

... the reason I ask is that I wanted to try and use p_cells->WritePointer()
to do the copying with a memcpy, but it looks like the format of a CellArray
is something like:

[cellid, pointid, cellid, pointid, cellid, pointid]

if i had 2 points per cell it would be
[cellid, point1, point2, cellid, point1, point2, etc]

if this is so, then in order to create a cellarray of 20 points, each in
their own cells, i'd need to alloc room for 40.


Am I reading the code correctly?
Does anyone do efficient copies, or does everyone use InsertNextEtc()
methods?

thanks,
Paul
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