[Chimera-users] lighting in Chimera

Tom Goddard goddard at cgl.ucsf.edu
Wed Nov 18 09:49:49 PST 2009

Hi Dan,

  Glad you liked Chimera glossy lighting.  It is computing the lighting 
at each pixel instead of at each surface vertex.  It also improves the 
appearance of transparent surfaces.  A patch of surface viewed nearly 
edge on appears more opaque then a face on patch because you are looking 
through a thicker section.  The normal lighting does not make this 
correction.  It makes the transparent surfaces look more 3 dimensional.

  A few other rendering quality improvements are in Chimera 1.4.  
Silhouette edges now work with transparent surfaces.  And there is a 
one-layer transparency option that shows only the front-most layer of a 
transparent surface.  This allows models underneath to be seen (e.g. a 
molecular model) without the confusing overlaps of parts of the surface 
in the back showing.  This is on by default for molecular surfaces 
(Actions / Surface / show) and is an option in volume data surfaces 
under the surface and mesh options panel in the volume dialog (default off).

  Interactive ambient occlusion lighting is hard, though definitely 
useful.  For special images you can sometimes fake it in Chimera as 
described here:


  Different surface inside and outside colors is on our request list, 
item 131, since feb 2008.


Would be nice.  Not too hard, but also it seems of value in limited 
circumstances since most clipped surfaces are "capped" i.e. the hole 
created by clipping is covered so the object appears solid, so the 
inside is not visible.


-------- Original Message --------
Subject: [Chimera-users] lighting in Chimera
From: Dan Gurnon
To: chimera-users
Date: 11/16/09 10:26 AM
> I wanted to tell you all that I love the new "glossy lighting" 
> feature- now its easy to see the difference between the inside and 
> outside of a surface when you use the per-model clipping tool. Without 
> it, I had a hard time getting a sense of depth when a surface was 
> clipped. But with the improvement glossy lighting brings, I have begun 
> to wonder if other improvements in coloring and lighting are in the 
> works or are possible. For instance, I use radial coloring with a grey 
> palette to help my students pick out tunnels and pockets in a surface, 
> but a better method would ambient occlusion on-the-fly. I've seen it 
> in the molvis program "Qutemol", though the program does little else. 
> Alternatively, is it possible to change the quality of shadows enabled 
> in the effects window? And on a separate note, is it possible to 
> change the inside color of a surface (something like "ribinsidecolor" 
> for surfaces?)
> Thanks
> Dan
> -- 
> ____________________________
> Daniel Gurnon, Ph. D.
> Assistant Professor of Chemistry
> DePauw University
> Greencastle, IN 46135

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