[Chimera-users] same volume data values over the entire volume

[Elaine Meng]

Hi Dieter,
I don’t know specifically what’s happening in your case, but if you are coloring an isosurface of the same volume data, by definition all the values would be essentially the same.  Coloring by the volume data value would normally be used on a slice of that isosurface, e.g. as shown here:

<http://www.rbvi.ucsf.edu/chimera/data/tutorials/volumetour/volumetour.html#colorcap>

I hope this helps,
Elaine
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Elaine C. Meng, Ph.D.                       
UCSF Chimera(X) team
Department of Pharmaceutical Chemistry
University of California, San Francisco

> On Jul 21, 2019, at 5:36 AM, Dieter Blaas <dieter.blaas at meduniwien.ac.at> wrote:
> 
> Hi,
>     Trying to color a volume according to "volume data" I get the same numerical values for all colors and a speckled appearance. When using "volume data gradient norm" I get the expected colors, i.e. strong local changes of the volume data are red and spots where there is essentially no change are in blue. How is this possible? If I understand correctly, "volume data gradient norm" colors according to the first derivative of "volume data" or is this wrong?  Do I need something like a normalization?
> Thanks a lot for explanations,
> best, Dieter