set_shading question

[Paul van Delst <paul.vandelst(at)noaa.gov>]

Hey there,

Can anyone enlighten me as to the LIGHT keyword to set_shading? The online docs state:

LIGHT
A three-element vector that specifies the direction of the light source. The default light
source vector is [0,0,1], with the light rays parallel to the Z axis.

How does one change the direction of illumination? I want to change the shading so I can
specify a source point (say [1,0,1] in a unit cube) and a "destination" point (say,
[0,1,1]) to define the light source direction, i.e. where the light is going *to*. Or is
this stuff like wind direction, i.e. you specify where the light is coming *from*?

thanks for any info

paulv

p.s. I'm using this for shading a surface in SHADE_SURF.

-- 
Paul van Delst           A little learning is a dangerous thing;
CIMSS @ NOAA/NCEP        Drink deep, or taste not the Pierian spring;
Ph: (301)763-8000 x7274  There shallow draughts intoxicate the brain,
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                                         Alexander Pope.