"Planets" has been revised in order to use color (maybe) on the MAC II. Additional enhancements in version 2.00 :
1. Now allows one to limit the minimum size a planet will shrink to.
2. Allows one to set the planet size to a fixed one-pixel size.
3. Supports continuous scrolling.
4. Supports color settings of planets (this I have not seen, let me know if it works).
5. A little more (note the word "little") coherent scheme for the "Planets Editor" dialog.
6. More useful "Windows" menu.
The "Launch" menu has been removed as per suggestions in Apple tech notes as to future incompatibilities with future "Finder"s.
As before, the program uses 80-bit floating point math for all calculations and thus can take advantage of MACs that contain the 68881 coprocessor. Speed improvement should be quite significant.
Windows should grow to full MAC II screen sizes.
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.
The "New Planets" window displays the current position while the "Old Planets" window displays the previous positions. The "Data" window will scroll by the information associated with currently active planets window. Text scrolling can be halted by holding down the mouse button. The text will then stop after each planet's data.
Menu items, I hope, are self-explanitory.
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.
