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Question by ColinBurke · Dec 27, 2012 at 08:01 PM · randommath

Random.seed Repeating

Does anyone know why I might be getting repeating values by setting Random.seed. Even if I use a prime number I get a mirror effect. I'm not even multiplying it my anything:

         Random.seed = 3;
         int value = Mathf.RoundToInt(Random.Range(-10, 11));

This essentially is called again for every block the world, returning value (see picture below):

![alt text][1]

What might be causing this? [1]: /storage/temp/6122-img.png

img.png (2.5 kB)
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avatar image Lovrenc · Dec 27, 2012 at 08:08 PM 0
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Well Random is just a function that is suppose to give you random numbers. In this case you seem to get undesireable graph. Nothing is limiting you though, to search for a Random class online and get what you need.

avatar image Screenhog · Dec 27, 2012 at 08:12 PM 0
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Why do you need Random.seed? Are you needing to make something that is random, yet reproduceable later?

avatar image Bunny83 · Dec 27, 2012 at 08:15 PM 0
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It's not clear how you use the random generator. If you set the seed manually to a fix number you will always get the same sequence of numbers. True randomness isn't possible since it's a pseudo-random-generator. That's why the seed is usually initialized with the current date / time. That ensures that each time you start your application you get a different sequence.

Again, show and tell us how you actually want to use the generator.

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Answer by Dave-Carlile · Dec 27, 2012 at 08:12 PM

Each time you set Random.seed the generator gets reset. So if you're setting the seed in Update, then grabbing a random number, you'll always get the same value. Set the seed in Awake or Startup instead.

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avatar image Lovrenc · Dec 27, 2012 at 08:14 PM 0
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Oh i didnt even notice he is setting the seed every time. This is your answer.

avatar image ColinBurke · Dec 27, 2012 at 08:28 PM 0
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Yep, this fixes it. Thanks and sorry for not being more specific.

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Answer by Eric5h5 · Dec 27, 2012 at 08:15 PM

You need to post more code; it's not clear what you're doing. This produces no mirror effect:

 Random.seed = 3;
 for (var i = 0; i < 300; i++) {
     Instantiate (prefab, new Vector3(i, Random.Range(-10, 11), 10), Quaternion.identity);
 }

Also you don't need Mathf.RoundToInt, since Random.Range when used with integers already returns an integer.

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