[vtk-developers] Add GetPoint function to vtkStructuredGrid

[David Doria]

On Fri, Feb 5, 2010 at 5:15 PM, David Gobbi <david.gobbi at gmail.com> wrote:

> The extents can become negative as a result of vtkImagePad, for
> instance.  The only way to use it to pad on the bottom or the left is
> by setting the OutputWholeExtent so that it starts at a negative
> number.  Yikes!  Also any filters that do "extent translation" can
> lead to negative extents.
>
> The tests don't cover negative extents, so when they occur, it's
> guaranteed that some downstream filter is gonna choke on them because
> it "assumes" that extents are always positive.
>
>   David
>

Ah yes yes, extents can be negative - how about this then?

void vtkStructuredGrid::GetPoint(int x, int y, int z, double p[3])
{
  int extent[6];
  this->GetExtent(extent);

  if(x < extent[0] || x > extent[1] ||
     y < extent[2] || y > extent[3] ||
     z < extent[4] || z > extent[5])
    {
    return; // out of bounds!
    }

  //get relative coordinates to the "lower left" grid corner
  int xrel = x - extent[0];
  int yrel = y - extent[2];
  int zrel = z - extent[4];

  int ind = zrel*dims[1]*dims[0] + yrel*dims[0] + xrel;

  grid->GetPoint(ind, p);
}

Thanks,

David
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