Random seed

Learn repeatable randomness with the same seed.

Random Seed and Determinism

Randomness in computing is pseudo-random. Pseudo-random number generators initialize from a starting value called a Seed.

// The same seed always produces the identical sequence
Random.InitState(42);
int num1 = Random.Range(1, 100);

Using the identical seed causes the generator to yield the exact same sequence of pseudo-random numbers every time, a property known as determinism.

Seed Sharing and World Synchronization

In multiplayer titles, sending entire world datasets across the network is unnecessary; transmitting a single seed integer (e.g. 94821) suffices.

public void SetWorldSeed(int seed) {
    Random.InitState(seed);
}

Both clients run the procedural generator locally with that shared seed, producing identical map topology.

Exercise Deterministic generation with seed

Define a Start method. Inside, declare int seed = 42; and print "Kullanilan tohum: " + seed to the console using Debug.Log.

Show example solution

using UnityEngine;

public class SeedTester : MonoBehaviour
{
    void Start()
    {
        int seed = 42;
        Debug.Log("Kullanilan tohum: " + seed);
    }
}

Test yourself

What occurs in Unity when Random.InitState(seed) is called with the identical seed value?
- The game immediately crashes and closes
- Character speed doubles every frame
- All game save files are deleted
- The random number generator produces the exact same sequence of numbers each time
Show answer

The random number generator produces the exact same sequence of numbers each time — The same seed resets the pseudo-random generator state, ensuring subsequent outputs occur in the exact same sequence.

Initialize random state

Random.____(seedValue);

Show answer

Random.InitState(seedValue);

Randomness and seed concepts

Seed

Seed value starting the generator
Random.InitState

Unity method configuring the seed value
Deterministik

Same input always gives same output
Pseudo-random

Fake randomness made by algorithms

Next lesson: Perlin noise

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