[vtkusers] bounds argument in vtkBox::IntersectWithLine()

[Maarten Beek]

But voxels of a CT (MRI) image cannot be considered infinitesimal thin, can they?
Maarten
 


     On Wednesday, March 18, 2015 3:16 PM, David Gobbi <david.gobbi at gmail.com> wrote:
   

 You can define "outside" to be whatever you want, but VTK defines "outside the bounds" to mean "beyond the data points that form the edge of the data set."  :)
If, for example, I wanted to intersect a line with the first and last slice of the volume, I would _not_ add 0.5*spacing.  But that's because I consider my "slice" to be an infinitesimally thin object.  So according to my definition of "slice", the distance between one end of the volume and the other is 99 times the spacing.
Really, how you define things will depend partly on the requirements of your application.  I'm just saying what my own definitions are.
 - David

On Wed, Mar 18, 2015 at 12:58 PM, Maarten Beek <beekmaarten at yahoo.com> wrote:

Hi David,
To clarify.Since "the bounds of avolume start and end in the center of the corner voxels.", I would have to expand the bbox in all directions by 0.5*spacing to get the intersections with the 'outside' planes of the image? And the distance between one 'outside' and its opposite 'outside' would be 100 times the spacing?

Maarten
 


     On Wednesday, March 18, 2015 9:42 AM, David Gobbi <david.gobbi at gmail.com> wrote:
   

 Hi Maarten,
If you used (0, 13, ...) then you'd get the wrong answer.  The bounds of avolume start and end in the center of the corner voxels.  If the first voxelis 0 and the last voxel is 99, then the real-world dimension of the volume is99 times the spacing.
A voxel is a data point.  Emphasis on "point".  If you have a series of datapoints, anything before the first point or after the last point is outside of thebounds of the data points.
 - David  

On Wed, Mar 18, 2015 at 7:23 AM, Maarten Beek via vtkusers <vtkusers at vtk.org> wrote:

Hi all,
For an image with dims = (100, 100, 100) and spacing = (0.13, 0.13, 0.13), vtkImageData::GetBounds() returns(0, 12.87, 0, 12.87, 0, 12.87)
If I use these bounds as argument in vtkBox::IntersectWithLine, do I get the correct intersections?Or should I use (0, 13, 0, 13, 0, 13) for the bounds?
Thanks - Maarten






   



  
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