Re: adding illumination to hemisphere (-JG)

Hi Pasquale,

I tried to do something like what you want but it is quite complicated  
to do it right because we must take into account the area of  
??twilight and the night zone on the planet.

I ended up making a grid with the height of the Sun above the horizon  
around the planet and using this grid to paint with grey and  
transparency. In the end I made a transparent PDF and converted it to  
PNG.

Regards, Eduardo.-

Quoting Pasquale Tricarico <[email protected]>:

> Hi,
>
> I am using GMT 4.5.12, using grdimage and -JG projection to obtain an
> hemisphere view of a planet. I would like to add illumination, i.e. by
> specifying
> the lat/lon of the sun, so that the correct part of the hemisphere is
> illuminated and the other part is much darker, but still visible. It
> looks like grdgradient may not be able to do this as it would have a
> fixed azimuth for illumination, maybe by using grdmath? Any
> suggestions will be greatly appreciated.
>
> Regards,
> Pasquale
>
> --
> Pasquale Tricarico, Ph.D.
> Planetary Science Institute
> http://orbit.psi.edu/~tricaric
>
> To unsubscribe, send the message "signoff gmt-help" to   
> [email protected]
>



-- 
Eduardo A. Suarez
Facultad de Ciencias Astronómicas y Geofísicas - UNLP
FCAG: (0221)-4236593 int. 172/Cel: (0221)-15-4557542/Casa: (0221)-4526589


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