I would like to have a composition that chooses a random number
ONLY ONCE, when it's first started.
Using the "Random" object results in a new random being generated
every time a frame is drawn. How can I make sure the first number
that is chosen is "frozen"?
Thanks,
-Michael.
You could use a JavaScript with one output and two inputs that
looked something like this:
if (outputs[0]==undefined){
outputs[0]=math.random*(inputs[1]-inputs[0])+inputs[0]
}
This will set the random output to a number between the inputs on
the first run and nothing after that.
Alfred
This won't work on screen savers. Math.random() has a nasty habit of
returning the same result every time (when launching a screen saver
from hot-corners or by waiting, not when clicking "Test" in the
Screen Saver control panel). In fact the code above won't work at all
because there is a small syntax error in it.
One solution is to manipulate Math.random() using some component of
Date() to get some other result. Maybe looping over Math.random() X
times, where X is the value of milliseconds in the date it the start
of your composition (this was suggested by Dave Hayden to me a while
ago). This is fine if you just want a seed for an integer between 0
and maybe 100, but doesn't cut it if you need some *real* randomness
in your screen-saver. Reason being that any N iterations of
Math.random() will always have the same result when run as a screen-
saver (my guess is that it isn't being seeded correctly in that
mode). It also causes a slow-down on initialisation of the
composition to do anywhere up to 1000 calls to Math.random(). But
here's the code anyway...
if (!outputs[0]) {
var myD = new Date();
var myM = myD.getMilliseconds();
var myR;
for (i = 0; i < myM; i++) {
myR = Math.random();
}
outputs[0] = myR;
}
Another alternative is to use this randomiser macro that I adapted
from existing code utilising the Mersenne Twister random number
generator algorithm. It's quite a bit more random than the standard
javascript random. Plus it can be called multiple times after one
initialisation, possibly making it faster to use for multiple random
calls. Be aware that this has some copyright usage restrictions from
the authors of the original algorithm - details in the javascript
code comments. Hopefully it isn't too big for the list.
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