[vtkusers] What is extent, actually?

[Tanya S]

Hello there?
   
  I thought extent means spacing multiply by dimension, but then I doubt it since from my vtkImageData, I get the spacing using GetSpacing() and it gives:
  spacing[0] = 2
  spacing[0] = 2
  spacing[0] = 3.125
   
  and GetDimensions() gives:
  dimension[0] = 128
  dimension[1] = 128
  dimension[2] = 94
   
  but then, GetExtent() gives:
  extent[0]=0
  extent[1]=127
  extent[2]=0
  extent[3]=127
  extent[4]=0
  extent[5]=93
  means extent in x direction = 128, extent in y direction = 128, 
  and extent in x direction = 94.
   
  And my other questions are:
  What is the difference between UpdateExtent, wholeExtent, and Extent of vtkImageData?
   
  Thx beforehand.
   
  Best regards,
  .Tanya.

			
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