"Planets" has been revised in order to use color. Additional enhancements and bug fixes in version 2.11 over 2.00 :
1. Now allows you to save a DATA file of the current system for later use.
2. Allows saving on a continuous basis each system snapshot to a TEXT file.
3. Supports continuous scrolling.
4. Corrects color problem which caused windows to retain the foreground color of the last planet displayed.
5. "Planets Editor" dialog allows a "Quit" immediately after opening.
6. Planets are drawn in the order of "most distant first" so that color systems will show color overlapping in the proper perspective.
7. Windows will open upon start-up to the full port size for users with large monitors.
8. The "Data" window option has been removed.
9. Will run in the background under MultiFinder.
10. Double-clicking Planets-created files will launch Planets. DATA files will load automatically, TEXT files will simply launch the application.
11. Application defaults on launch to a single planet with location = 0,0,0 m, velocity = 0,0,0 m/s, size = 1m, viewpoint = 10,0,0 m, and time increment = 1 sec.
As before, the program uses 80-bit SANE floating point math for all calculations and thus can take advantage of MACs that contain the 68881 coprocessor. Speed improvement should be significant (actually about 4-5 times) but not as fast as would be possible with direct 68881 support.
In general :
The program, as it now stands, limits the maximum number of planets to 20. You may have any number of planets in your system within this range.
Orbits are 3-dimensional. You may set any velocity and/or position vector as well as size and mass within the limits of SANE's EXTENDED type range (+/-1.1E4932).
The "X" axis extends into the screen with "Y" straight up and "Z" to the right. This coordinate system applies to all vectors. Note that planets that are located with their center behind your "X" axis position are not displayed regardless of their diameter.
The "New Planets" window displays the current position while the "Old Planets" window displays the previous position.
Menu items, I hope, are self-explanatory.
This program uses an incremental calculation of movement in order to calculate the next set of planet positions. This means that greater time increments, as set in the "System Data" dialog, will result in greater movement per calculation but also greater incremental error.
This program was originally written in Modula-2 for the MACMETH compiler from Modula Corp. The current version has been modified to compile under TML's Modula tool for the MPW. If anyone is interested in the source code, let me know.
Future revisions will support printing, database-like text saves, a help file, and a "direct-access to the 68881" option for much greater calculation speeds.
