[Chimera-users] limits of transparency?

Greg Couch gregc at cgl.ucsf.edu
Tue Dec 9 12:14:34 PST 2008

On Tue, 9 Dec 2008, lvyuan zhang wrote:

> Hi,
>      I'm making my protein ribbons partially transparent by changing the 
> alpha value in color editor.  I tried a=0.2 and a=0.05, and I found that 
> after raytracing, there is no difference between these two. Isn't a=0.05 
> supposed to be more transparent? Is this a bug or something is wrong 
> with some settings in chimera that I don't know? Thanks a lot first!
> Cheers!
> Luyuan Zhang

POV-Ray uses a different lighting model than chimera, so the lighting will 
never match exactly.  Chimera colors are currently converted to POV-Ray 
rgbf colors.  I don't recall why that choice was made, but changing to 
rgbt colors appears to mimic chimera better.  I will make that change and 
it will appear in the next daily build.  If you want to test out the 
change right now, change your POV-Ray Options so that "Keep POV-Ray input 
files" is true, then edit the resulting image.pov file and replace all of 
the rgbf's with rgbt's, and rerun POV-Ray with:

 	CHIMERA/bin/povray +Iimage.pov +Oimage.png image.ini

Please let me know how you like the new version,

 	Greg Couch
 	UCSF Computer Graphics Lab

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