This Macintosh After Dark module draws animated, fractal clouds.
Settings
The "Colors" menu lets you select a color scheme for your clouds.
"Wispiness" lets you vary the fractal dimension from 2.15 to 2.45.
"Wind" makes the clouds move. (A southwest wind moves them up and to the left.) Set to "Random" to change the direction each time the module is started.
"Redraw Speed" controls how fast new cloud formations appear.
System Requirements
Clouds requires 32-bit QuickDraw, i.e. System 6.0.5 or higher and a Macintosh with 68020 processor or higher. Clouds is optimized for running on its own, on a single screen in 256-color mode. In other environments, it may be much slower or give unsatisfactory results.
When running Clouds under MultiModule (as demonstrated by the enclosed settings file, Landscape), you should set the screen to more than 256 colors.
Algorithm
Clouds uses a simplified version of the MidPointFM2D random midpoint displacement algorithm by D. Saupe (without random additions, with circularized boundaries, and fixed initial values). Fractal values are used as color indices without any scaling.
Hacking Clouds
You can edit the color tables ('clut' resources) of Clouds with ResEdit, as long as color # 0 and 255 remain white and black, respectively. When adding a new 'clut' resource, you must also add an appropriate entry to 'MENU' 1000.
At your own risk, you can change the value of 'mLvl' resource 128 to increase the final resolution. A change of 1 increases the resolution and memory requirement by a factor of 4, up to the amount of memory available. To make the modified module work under MultiModule or Randomizer, you must also change the value of 'sysz' resource 0 by a factor of 4.
Changes in Version 1.1
* Random setting added to "Wind" slider.
* More "Wispiness" and "Redraw Speed" settings.
* Faster through use of 68020 code.
* Should be more compatible with QuickDraw accelerators.
While Clouds is stable on all Macs with internal video, the present version may still crash some QuickDraw accelerator cards - use at your own risk!
Thanks to everyone who sent comments and suggestions, and to GR and José Casal for testing.
Developed with Think C 5.0 and After Dark 2.0.
Algorithm adapted from: Saupe, D. (1988). Algorithms for random fractals. In: The Science of Fractal Images, H.O. Peitgen and D. Saupe, eds. (New York: Springer-Verlag), pp. 71-113.
