Unity：索引超出数组范围

Question

im developing with Unity for about a year now and very often I got this Error: IndexOutOfRangeException: Index was outside the bounds of the array. I know that that error means that the given index is bigger then the array itself. But I dont think that the Array is bigger than the used value.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class ProceduralGeneration : MonoBehaviour
{
public GameObject[,] tiles = new GameObject[3000, 3000];
public GameObject[] prefabs;
int sizeyet = 0;
GameObject obj;
public int renderdistance;

int[,] map;

// Start is called before the first frame update
void Start()
{
    map = CreateMap(map);
    for (int i = 0; i < map.Length; i++)
    {
        for (int j = 0; j < map.Length; j++)
        {
            
            
            obj = Instantiate(prefabs[map[i,j]], new Vector2(i, j), Quaternion.identity);
            tiles[i, j] = obj;

            
        } 
    }
}

public int[,] CreateMap(int[,] map)
{
    map = new int[4000, 4000];
    for(int i = 0; i < 3000 - 1; i++)
    {
        for(int j = 0; i < 3000 - 1; j++)
        {
            map[i, j] = Mathf.RoundToInt(Mathf.PerlinNoise(i, j) * 10);
        }
    }
    return map;
}

// Update is called once per frame
void Update()
{
    
}

}

I very often canceled project because I couldn't fix this error.

If my English is not so good, excuse me. Im a german student.

Answer 1

There are a few problems here. Firstly, there's a typo in CreateMap :

for(int j = 0; i < 3000 - 1; j++)

Note how you're using i in the condition instead of j - so that loop will never terminate, assuming that i is less than 2999 to start with. But even changing that won't fix the bigger problem. Let's look at the rest of the code.

Here's how you initialize map :

map = new int[4000, 4000];

And here's how you initialize tiles :

public GameObject[,] tiles = new GameObject[3000, 3000];

So map.Length is 16000000, because that's the total size of the array .

Now let's look at your loop:

for (int i = 0; i < map.Length; i++)
{
    for (int j = 0; j < map.Length; j++)
    {
        obj = /* irrelevant */
        tiles[i, j] = obj;
    } 
}

So your code is a bit like this:

GameObject[,] tiles = new GameObject[3000, 3000];
for (int i = 0; i < 16000000; i++)
{
    for (int j = 0; j < 16000000; j++)
    {
        tiles[i, j] = something;
    }
}

Can you see how that's clearly going to go way out of bounds?

Even if the code behaved as you expected it to, tiles is 3000x3000 and map is 4000x4000, so that would be a problem.

I suggest you create some constants, and use those everywhere:

private const int MapWidth = 4000;
private const int MapHeight = 4000;

public GameObject[,] tiles = new GameObject[MapWidth, MapHeight];
...

// Then later...
for (int i = 0; i < MapWidth; i++)
{
    for (int j = 0; j < MapHeight; j++)
    {
        tiles[i, j] = ...;
    }
}

// And in CreateMap:
map = new int[MapWidth, MapHeight];
for (int i = 0; i < MapWidth; i++)
{
    for (int j = 0; j < MapHeight; j++)
    {
        map[i, j] = Mathf.RoundToInt(Mathf.PerlinNoise(i, j) * 10);
    }
}