• #### Algorithm for AfterDark's 'Rose' - trigonometry

From chrismear@gmail.com@21:1/5 to Christopher Mear on Wed Jun 13 08:04:25 2018
On Thursday, 21 August 1997 08:00:00 UTC+1, Christopher Mear wrote:
Does anyone remember the screensaver 'Rose' from the After Dark
screensaver?
It basically draws several dots on the screen which move about in
circular patterns.
(It also uses colour cycling and trails to give a nicer effect)

The help file said it used trigonometry, but nothing beyond that.
I assume it's something to do with polar coordinates.

Can anyone enlighten me?

Twenty years later...

The original developer of the Rose screensaver has revived it to work on modern releases of macOS, and has released it as freeware:

http://www.sticksoftware.com/software/Rose.html

Chris

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• From Noskosteve@21:1/5 to chri...@gmail.com on Wed Jun 13 17:49:31 2018
For my laser light show software I had what I called my Circle Generator. A Sine and Cosine, one for horiz and the other for vert.

By stepping the angle small amounts, you get a circle.
By using varying amounts you can get many patterns, not just a circle; some still and some animated.

Stepping in 90 degree steps you get a square. 89 or 91 degrees is a slowly rotating square. 72 degrees is a star and 71 or 73 is a rotating star.
There are endless possibilities once you understand what's going on and get some experience picking increments and ways to vary the variables.

You can also step the two angles as well as the two radius variables (the sin & cos Magnitude) in unison or independently. I got many good patterns and burned them into one show in ROM and bring that projector out front every Halloween.

The image on that web page looks like it used mirroring which I didn't.
By stepping the angle in really large steps, you can also get artifacts from the trig algorithm of the software you use.

On some I added Z axis rotations.

Regards, Steve Noskowicz

On Wednesday, June 13, 2018 at 10:04:29 AM UTC-5, chri...@gmail.com wrote:
On Thursday, 21 August 1997 08:00:00 UTC+1, Christopher Mear wrote:
Does anyone remember the screensaver 'Rose' from the After Dark screensaver?
It basically draws several dots on the screen which move about in
circular patterns.
(It also uses colour cycling and trails to give a nicer effect)

The help file said it used trigonometry, but nothing beyond that.
I assume it's something to do with polar coordinates.

Can anyone enlighten me?

Twenty years later...

The original developer of the Rose screensaver has revived it to work on modern releases of macOS, and has released it as freeware:

http://www.sticksoftware.com/software/Rose.html

Chris

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)