[Chimera-users] Povray and semitransparent maps

Elaine Meng meng at cgl.ucsf.edu
Fri Aug 29 11:17:32 PDT 2008

Hi Jason,
You can change (a) overall lighting and (b) lighting behavior of the  
surface itself.

(a) Chimera uses two lights, "key" and "fill" where (by default) only  
the key light produces shiny highlights and shadows in raytraced result.

You can adjust these lights' brightness, positions (directionality),  
and key/fill ratio in the Lighting tool (under Tools... Viewing  

In general decreasing the key-to-fill ratio increases ambient  
illumination, so you could try that and/or increasing the overall  

Besides the lighting, it might help to adjust properties of the  
surface itself in Chimera.  I assume you are showing an isosurface  
since I don't think transparent solids work with raytracing.  Select  
the surface model such as with Ctrl-click or using the Model Panel,  
and then open the Selection Inspector (green button near bottom right  
corner).  Inspect "Surface piece" - you will see some lighting-related  
parameters that can be adjusted.  "lighting, transparency" dim =>  
bright seems promising, although I admit I have not played with this  
parameter when raytracing.

I hope this helps,
Elaine C. Meng, Ph.D.                          meng at cgl.ucsf.edu
UCSF Computer Graphics Lab (Chimera team) and Babbitt Lab
Department of Pharmaceutical Chemistry
University of California, San Francisco

On Aug 29, 2008, at 7:48 AM, odonnell at chem.fsu.edu wrote:

> Hi. I'm seeking a tip or two on how to save an image of a
> semitransparent map with PovRay.  Povray works fine, but the image of
> the semitransparent map it generates is much darker that it appears on
> the screen. Any advice would be much appreciated.
> -Jason

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