How to spawn prefabs with percent random?

Question

I need to instantiate 3 different prefabs.

First prefab must spawn with 50 %

Second prefab must spawn with 30 %

Third prefab must spawn with 20 %

I know how to intantite objects, but i didnt know how to make percent random.

Answer 1

Best Answer

Answer by jogo13 · Jan 22, 2013 at 06:10 PM

Random.value returns a float between 0 to 1. You can use it to generate percentage random like so:

 if(Random.value > 0.5) //%50 percent chance
 {//code here
 }
 
 if(Random.value > 0.2) //%80 percent chance (1 - 0.2 is 0.8)
 { //code here
 }
 
 if(Random.value > 0.7) //%30 percent chance (1 - 0.7 is 0.3)
 { //code here
 }

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jister · Apr 16, 2014 at 04:55 PM 0

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what if it returns 0.6, then it would run the first and the second if statement...?

quantumface · Jun 16, 2015 at 03:51 AM 0

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Nope. On each of those if statements a new Random.value is generated. It would work as you've thought only if a variable has been set to be Random.value once, and then re-used in all those if statements.

GarMatt_ · May 31, 2020 at 05:22 PM 0

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Sorry for the necroposting here but isn't there a chance that it doesn't instantiate with that code?

ms11153 · Dec 03, 2021 at 08:05 PM 0

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I'm using this code for a chance of either having a health potion be dropped, or the player taking damage. Sometimes they both happen, or twice of one or another happen. Is there any way to fix this?

Answer 2

Answer by Kalbytron · Sep 09, 2013 at 11:15 PM

You can also say

if(Random.value

to get a %20 chance without the confusion.

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ofuscapreto · Jun 22, 2017 at 12:41 AM 0

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I think this is the best way, thanks!

DigitalCyclone · Jan 05, 2019 at 03:53 PM 0

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Wouldn't it be if(0.2 > Random.value)?

for example, say the random value generated a 30%

20% is NOT greater than 30%, therefore the if statement returns false.

however, when the random value generates something like a 15%

20 IS greater than 15, therefore the code will run.

David_Rios DigitalCyclone · Jun 18, 2019 at 10:18 PM 0

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That's the same thing as saying if(Random.value < 0.2) @DigitalCyclone; the <= is just to get the .20 along with all of the other values that are below it.

Armetron · Aug 29, 2020 at 09:04 PM 0

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problem with this is random.value is 0 to 1 [INCLUSIVE] which means that it is possible for the value to be 0, if the chance value was set to 0.0 which means it should never happen since your using <= then there is a slight chance that it could fire.

Answer 3

Answer by unity_973D59F5B05CFF0E9822 · Aug 01, 2021 at 07:26 AM

 public float Chance()
 {
     float[] chances = new float[] { 0.5f, 0.3f, 0.2f }; // Your chances. Summary = 1.0f
 
     float randValue = UnityEngine.Random.value; // Randome value (chance value)
 
     float currentChance = 0f;
     float minChanceRange;
     float maxChanceRange;
 
     for (int i = 0; i < chances.Length; i++)
     {
         currentChance += chances[i];
 
         minChanceRange = 0.5f - currentChance / 2;
         maxChanceRange = 0.5f + currentChance / 2;
 
         if (randValue >= minChanceRange && randValue <= maxChanceRange)
         {
             return chances[i]; //code here
         }
     }
 
     return -1; //This code unreacheble
 }

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How to spawn prefabs with percent random?

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