[vtk-developers] Should ImageViewer2/ImageActor using "Spacing"

[Miller, James V (Research)]

I spent a few hours last night tracking down a problem with my use of ImageViewer2. Since
ImageViewer2 uses the 3D rendering pipeline, I was tricked into thinking it would be trivial to use
the ImageViewer2 to show an intensity image and I could simple add another actor to the
ImageViewer2's renderer to display a segmentation overlaid on the intensity image.  The segmentation
technique uses level sets so I used Marching Squares to extract the zero set as PolyData to overlay
on the image.  
 
Now, the output of Marching Squares did not line up properly with the original image.  I believe the
issue is that Marching Squares took into account the data spacing while the ImageViewer2/ImageActor
combination does not take into account the data spacing.
 
I know that we have struggled with this in the past, but should the ImageActor use the pixel spacing
to determine the "bounds" (and hence the projection) of the image? 'Course sometimes you do want to
view an image as if the pixels were isotropic or unit size.  Perhaps it could be a mode to turn
on/off pixel spacing.
 
I has a number of options to get around this issue, scaling my polydata actor, using
ImageChangeInformation, etc. so it wasn't too hard to get around.  However, it did take me awhile to
determine the use and lack of use of the data spacing was what was causing my grief (I had assumed
the problem was with my multi-resolution scale space, not with the rendering...)

 <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

Jim Miller 
_____________________________________
Visualization & Computer Vision
GE Research
Bldg. KW, Room C218B
P.O. Box 8, Schenectady NY 12301

millerjv at research.ge.com <mailto:millerjv at research.ge.com> 

james.miller at research.ge.com
(518) 387-4005, Dial Comm: 8*833-4005, 
Cell: (518) 505-7065, Fax: (518) 387-6981 

 

 
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