Bernd Brinkmann Jan 29, 2004
> Hmmm... a few comments:Clear skies
>
> To get the color right, change
>
> f 112 30 10 0
>
> to
>
> f112 30 10 0
>
> I hadn't tested out fills with more than a hundred points before.
> Turns out Guide reads the color of your current example as "2 30 10"
> (ignoring the final 0) rather than the intended "30 10 0".
>
> But a more basic problem is that you've got a fill that goes all
> the way around the sky, so to speak, right through a mathematical
> singularity at the point opposite the screen center. Depending on
> what projection you've selected in Settings... Projection, this
> will cause some sort of display error. In the (default) stereographic
> projection, for example, the point opposite the screen center,
> at the "antipodes", projects to undefined points infinitely far away.
>
> There are a couple of ways of getting around this. One would be
> to break up the whole shape into several shapes, each covering
> (say) 45 degrees in azimuth. When Guide gets to the shape that is
> "behind" you (or at all off-screen), it simply doesn't draw it,
> so there is no display error associated with it.
>
> The other way, which I'd recommend, is to use Guide's ability
> to show an "horizon" in the manner described at
>
> http://www.projectpluto.com/update7c.htm#easier_horizon
>
> If you set your "home planet" to be the Moon, you can see an
> example of this (and you can see how it's done by looking at the
> file 'horizo10.dat'). In your situation, I'd create two such
> horizons, one at positive altitudes and another at an altitude
> of -20 degrees.
>
> I've revised your 'horizon.dat' file accordingly. You'll see
> that this basically involved replacing a 'fill' command with some
> 'hor' commands. I made the -20 piece of a slightly different
> shade, just enough so one can tell it's not quite the same.