[Chimera-users] odd glare when volume rendering

Tom Goddard goddard at cgl.ucsf.edu
Fri Aug 3 13:08:15 PDT 2007

  Elaine points out that "no color" for depth cueing really uses the 
background color, not necessarily black or white as I said in my 
previous message.

  The "glare" problem in volume rendering becomes apparent only when the 
background color has differing non-zero red, green, or blue components!  
Why?  Because volume rendering sums up these color values for planes at 
many depths, but the sum for each of the RGB components is clamped to a 
maximum of 1.  So with background color, say RGB = (1, 0.5, 0) the sum 
of the depth cue color on the planes ends up being (1, 1, 0) due to the 
clamping which is a different color, not matching the background and it 
looks like a bright brick in the volume rendering.


Elaine Meng wrote:
> Technically, "No color" makes depth cuing use the same color as the 
> background (not necessarily either black or white), but close enough 
> for the purposes of your discussion!
> On Aug 3, 2007, at 12:30 PM, Tom Goddard wrote:
>> If you have depth cueing set to "No color", which
>> is the default, *and* you use a light background color, then Chimera
>> interprets "no color" as white.  With a dark background color, I use
>> black, "no color" for depth cueing is interpreted as black.

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