Best way to offset the randomization of values

[magneto]

When generating random values for different parameters using the rand expression, I see people multiplying the result with a value, or adding a value to the result, etc.

Which way is the most preferred way that gives the most chaotic results?

Is it enough to just do something like?

x = rand($PT)

y = rand($PT) + 1

z = rand($PT) + 2

I feel this will not provide as much difference for instance.

What are the best practices?

I am sure Houdini experts would have their consistent methods they always use regardless.

Thanks

[symek]

x = rand($PT)
y = rand($PT+0.1)
...

more likely

Also from Help:

Note

It is a good idea to use non-integer values as the argument to rand().

Edited March 4, 2012 by SYmek

[magneto]

Thanks Symek. I read that but didn't realize that's what it exactly meant till you pointed out.

[thinkinmonkey]

Magneto,

what SYmek suggested is right. You have to remember that random doesn't mean a casual number, but if you give the same seed to the function, you'll obtain the same result:

rand(5) = rand(5)

Now my formulas normally use big numbers for the seed, float numbers as SYmek says, and I use a little trick, let's say, to remember those numbers, in order to change always seeds:

My formulas are something like this:

x = rand($PT*159.357+741.23)
y = rand($PT*951.753+486.624)
z = rand($PT*426.684+123.654)

If you try to digit the above numbers on your numpad, you'll see soon they are numbers taken following diagonals (951.753, 159.357), "L" shapes (741.23), "Diamond" shapes (426.684), "dumb" shape (123.456 ), etc.

It's like a "finger ballet", in this way I (should ) know to not use that kind of shape for next combinations or, if I'm in trouble, I simply copy/paste the previous formulas in different order, for example using the previous one, it will be:

x = rand($PT*741.23+159.357)
y = rand($PT*486.624+951.753)
z = rand($PT*123.654+426.684)

And don't forget that rand() gives you always values ranging in [0..1], so I quite often use it with fit01() function to control it better according to my needs.

Cheers.

[hopbin9]

I think these formulas over complicate it. If X is already a random value, then you already have the seed for the next random value.

x = rand($PT)
y = rand(x)
z = rand(y)

Edited March 4, 2012 by hopbin9

[thinkinmonkey]

Hopbin9,

YOU WIN!

Taking notes...

[magneto]

Thanks for the input guys. This is all interesting.

@thinkingmonkey, when you stared talking about diamond shapes, I thought you were trolling

What about using prime numbers though? From what I know that's a good way to offset randomization in general programming. Something like:

rand($PT * 13)

rand($PT * 17)

rand($PT * 19)

But I didn't realize the non-integer advantage for the rand expression.

[thinkinmonkey]

@thinkingmonkey, when you stared talking about diamond shapes, I thought you were trolling

Well, I didn't know how else to describe that!

But I didn't realize the non-integer advantage for the rand expression.

Never used integer with rand() in H.

[hopbin9]

rand($PT * 13)

rand($PT * 17)

rand($PT * 19)

Clever. I like it