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[IV3D-USERS] odd color volume bug?


Chronological Thread 
  • From: Colin Poczatek <jpoczatek@rics.bwh.harvard.edu>
  • To: iv3d-users@sci.utah.edu
  • Subject: [IV3D-USERS] odd color volume bug?
  • Date: Tue, 08 Mar 2011 11:08:16 -0500
Ok, I've convinced myself that this is a bug but as usual it's possible I'm wrong. It's possible that I broke our QVis export code, but I kinda doubt it.

Background: So we have multichannel data (16bit) and commonly view it in 2D by taking (Channel-A / Channel-B) (now a float) and mapping that to a hue scale and mapping Channel-B to alpha. We've been doing the same thing making color volumes (QVis format) and rendering in iv3d.

In the attached screenshot on the left there's a file I made a while back, and on the right is the same data with a different hue scale isosurface and 1dtf rendered. When I change the bounds on the hue scale so more voxels are saturated (ie close to max hue) those voxels aren't rendered as bright but appear very dark. This is apparent if you look at the "pink ball". This isn't an isosurface issue as you can see in the 1dtf view, with a clipping plane to show the interior of the "pink ball".

To double check that I was writing values that made sense, I ran the .raw part of the QVis file through unu and grabbed a little 3x3x3 nrrd from the center of the "pink ball" and looked at the bytes in a hex editor. RGBA values are all (212, 55, 212, 155) (+/- 1 or 2) which seem to me to be sensible values.

I've been looking at this for a while and I'm not sure what I could be doing wrong... Other things I've tried (no real change in what's rendered) are:
- level of anisotropy (varied from (1,1,0.2) to (1,1,1) )
- noise, tried higher medianization
- data size ( (256,256,450) to (256,256,90) )
- opening the color volume in other software (ImageJ), looks ok
- writing each channel individually and looking at those, looks ok

Really the only thing that seems special about these voxels that don't appear as I expect is that they're pink. :)
Thoughts?

Collin




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