Re: [Flightgear-devel] Moonlight

[Thorsten R. <tho...@sc...>]

>  To
> me it is logical that the moon illumination equations are located
> together with the moon phase equations in the ephemeris code in
> simgear/ephemeris/* and flightgear src/Environment/ephemeris.cxx.
> Where would you rather put the equations and why?

The reasoning is that taking the log of the light flux introduces a  
perception model beyond celestial mechanics, and ephemeris and perception  
filtering are conceptionally rather different things.

Also, in practical terms there may be a need to fine-tune such a filter  
together with changes to the shaders, and having it on FGData (as property  
rule) would give it the same level of accessibility.

And, also in practical terms, you could leave the current ephemeris code  
'as is', i.e. consistent for all celestial bodies, and the property rule  
would take care of untying for the effect framework.

> As for the moon-angle-rad property, I might have to do a little
> research to find exact values for --start-date-lat, --lat, --lon,
> --altitude, and --heading to have reproducible test cases where the
> UFO faces the moon and the moon position angles are 0, pi/2, pi, and
> 3/2pi,


This sounds like you think of the moon-angle-rad as something completely  
different from sun-angle-rad.

The sun angle is the angle between sun position above horizon and the  
zenith - it's zero if the sun is right in the zenith, it's pi/2 if the sun  
is at the horizon. That's independent on ufo attitude and even independent  
in which direction the sun is (doesn't matter for the angle if it's dusk  
or dawn, it's still pi/2) and just a function of how high the sky you see  
the sun.

What is the moon angle supposed to represent then if you need all these  
other values?


* Thorsten