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BlueBrain / NeuroMorphoVis

A lightweight, interactive, extensible and cross-platform framework for building, visualizing and analyzing digital reconstructions of neuronal morphology skeletons extracted from microscopy stacks.
https://portal.bluebrain.epfl.ch/
GNU General Public License v3.0
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Issue: discontinuous colormap for 3D directions (angle vs. sine) #139

Closed mihelics closed 3 years ago

mihelics commented 3 years ago

Hi Marwan,

Thanks again for adding the 3D directional color-coding feature...

I noticed some choppiness (discontinuities) in the colormap. Did you perhaps encode the angle to each axis or the sines of those angles in the colormap? I believe the sines of those angles (the 3-space components of the direction unit vector) to be the better quantity to encode because it will utilize the color-space more evenly.

Proof: a random variable uniformly distributed on the surface of the unit sphere will be uniformly distributed in three components (sine of angle from axis) independently, but will have an uneven distribution when binned by the angles.

For example, looking at this authentic in vivo anatomy:

image

Here is the histogram of segment directions binned by Z-component (quite uniform):

image

And here is the histogram of (area-weighted) section directions binned by angle from Z axis (the histogram is heavily concentrated on 0 (because a random direction is more likely to be aligned to a plane than a line).

image

Thanks, Sam

marwan-abdellah commented 3 years ago

@mihelics Is this for NeuroMorphoVis or VessMorphoVis?

mihelics commented 3 years ago

Oh sorry, my mistake. Let me try to move those to VessMorphoVis

пет, 29. окт 2021. 07:31 Marwan Abdellah @.***> је написао/ла:

@mihelics https://github.com/mihelics Is this for NeuroMorphoVis or VessMorphoVis?

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mihelics commented 3 years ago

I moved this issue over to vessmorphovis. will move my recent feature request too. Sorry about that. Good catch.