--------------------------------------------------------------------------
| Done
--------------------------------------------------------------------------

12/17/97 - Fix sun/moon initialization code so display lists aren't 
           re-created at every Init().

12/23/97 - First stab at a reasonable sky ... I'm going to probably
           leave this for now so I don't spend the rest of my life
           trying to tweak it.


--------------------------------------------------------------------------
| Todo 
--------------------------------------------------------------------------

12/29/97 - Timer/scheduler

12/29/97 - Unify sun position render code with existing sunpos
           calculations so the sun doesn't do it's little jump every
           hour.

12/29/97 - Scenery area manager

12/29/97 - View frustum culling

12/29/97 - Add a mechanism to parse command line options
    * A simple clear-screen sky.
    * No fog.
    * No astronomy.
    * Less detailed terrain.
    * Texture - but no MIP-mapping.
    * Texture - but no bilinear blending.
    * No texture.

12/29/97 - sky tweaking
  Steve Baker writes:
    So, by building the sky in the flattened shape, we can have it be
    very foggy at the horizon and clear blue overhead.

    The other important feature of this model is the colours. We
    colour each vertex of the dish individually to allow for cute
    sunsets, a darker blue overhead than at the horizon in daylight, a
    gradual darkening of the sky as a function of altitude for very
    high altitude flight - into space. Also we tint the horizon more
    in the direction of the sun so that sunset starts where the sun
    goes down - and the sky remains blue on the opposite side of the
    sky - then as the sun gets lower, the colour spreads outwards all
    around the sky and the black of night creeps in slowly from the
    opposite side of the sky from the sunset.

    We also like to tint the bottom edge of the sky with white - even
    in broad daylight - so it looks fuzzy - even when there is very
    little fog to achieve that effect.

    We use a text file that contains a lookup table relating the sun
    angle relative to the horizon to:

    *  The colour at the top of the sky dome,
    *  The colour of the horizon nearest to the sun
    *  The colour of the horizon farthest from the sun
    *  The colour of the texture environment blend for the clouds.
    *  The fog colour.

    We can then tweak that file to set up all the conditions. The
    realtime system interpolates the horizon colours all around the edge
    of the sky.

12/29/97 - Ground collision detection

12/29/97 - glut windows or something for panel area - consider 3d
           panels, careful of texture memory problems.
