[caret-users] Why does lighting and opacity selection not make any difference?

[John Harwell]

Lighting alters the surfaces colors by approximating the absorption  
and reflection of light on the surface.  Since lighting affects the  
surface coloring, some user's prefer to disable lighting for an  
overlay displaying functional (metric) data.  Lighting is applied only  
to three-dimensional surfaces.  Lighting is not applied to flat  
surfaces.  The overlay must be set to a Data Type other than NONE for  
the overlay's lighting control to have an effect.

Images showing metric data on primary overlay with and without  
lighting.  Notice that the surface without lighting loses its three- 
dimensional appearance.

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Opacity allows blending of the overlay with the underlaying coloring.   
If its value is 1.0, the overlay is opaque meaning that the overlay's  
coloring completely overrides any underlaying coloring.  If the  
opacity value is zero, the overlay is fully transparent allowing all  
of the underlaying color to show.  The overlay must be set to a Data  
Type other than NONE for the overlay's opacity control to have an  
effect.

Images with primary overlay set to metric and primary overlay opacity  
set at 1.0 and and 0.3.  With a low opacity, the underlaying sulcal  
pattern becomes apparent.


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Also see also: http://brainvis.wustl.edu/CaretHelpAccount/caret5_help/dialogs/display_control_dialog.html#OU_Surface


John




On Apr 13, 2009, at 1:25 PM, Yune S. Lee wrote:

>
> Dear caret users,
> I have a trivial question regarding lighting and opacity in the
> overlay/ underlay-surface .
> I've been playing around with lighting (check or uncheck) and opacity
> values to see what's changing in the graphic, but I didn't notice any
> difference in my workstation.  So, I wonder why this happens and  
> what I
> am supposed to see depending on different setting (e.g., what would  
> have
> happened when lighting
> is unchecked?) Any help would be appreciated.
>
> thanks,
> YSL
>
>
>
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