Allow more than one star system to be visible simultaneously.



Celestia To Do List
-------------------

USER INTERFACE
* More star label modes--nearest stars, brightest stars
* Add preferences for text color to config file
* Dialog box for displaying detailed information about a star or planet
* Star browser: flag stars with planetary systems
* Solar system browser: add icons
* Popup H-R diagram window
* Use a slider widget for controlling ambient light level
* Allow precise control of FOV

VISUALS
* Non-Lambertian illumination functions for planets
* Add haloes around bright planets similar to the ones around stars
* Comets with dust and ion tails
* Add some deep sky objects--planetary nebula, supernova remnants, etc.
* Procedural textures for extrasolar planets
* Bump mapped cloud layers
* Render galaxies with colors--bluish spiral arms, yellowish center
* Render dark dust bands in galaxies
* Add textures to Mir model
* Cloud shadows

POLISH
* Tutorial mode
* Add a flashy intro screen
* Preload some textures to avoid loading delay
* Use Greek letters in Bayer designations
* Make the demo loop
* Add a demo mode that visits random targets
* Compute accurate altitude above oblate planets/stars using point-to-ellipsoid
  distance function.
* Load add-ons from subdirectories of extras

SIMULATION ACCURACY
* Fix apparent magnitude calculation for planets
* Figure out a way to estimate gas giant's radius given its mass
* Make some attempt at calculating stellar rotation rates
* Model the chaotic rotation of Hyperion
* Double star systems: make the stars actually orbit each other
* Account for the finite speed of light
* Expand the galaxy database
* Use more intuitive/standard fields in galaxies file--instead of axis/angle
  orientations, use 'angle from face on' etc.

BUGS
* Fix wobbling of planet shadow on rings when time is accelerated
* Investigate possible visual anomalies with ring shadows on ATI Rage cards
* Fix slowdowns with ring shadows and night textures on ATI Rage cards

OPTIMIZATION
* Add option to force 16-bit textures

CODE
* Make parser more robust (and fix that EOF problem)
* Change random printfs to DPRINTFs and Logs
* Finish assert-ing the code

MISC
* Make solar system creation applet, for adding hypothetical systems to
  a Celestia universe
* Switch to UNICODE
* Internationalization
