Grid_part1.cs

using UnityEngine;

public class Grid : MonoBehaviour
{
    public float waterLevel = .4f;
    public float scale = .1f;
    public int size = 100;

    Cell[,] grid;

    void Start() {
        float[,] noiseMap = new float[size, size];
        (float xOffset, float yOffset) = (Random.Range(-10000f, 10000f), Random.Range(-10000f, 10000f));
        for(int y = 0; y < size; y++) {
            for(int x = 0; x < size; x++) {
                float noiseValue = Mathf.PerlinNoise(x * scale + xOffset, y * scale + yOffset);
                noiseMap[x, y] = noiseValue;
            }
        }

        float[,] falloffMap = new float[size, size];
        for(int y = 0; y < size; y++) {
            for(int x = 0; x < size; x++) {
                float xv = x / (float)size * 2 - 1;
                float yv = y / (float)size * 2 - 1;
                float v = Mathf.Max(Mathf.Abs(xv), Mathf.Abs(yv));
                falloffMap[x, y] = Mathf.Pow(v, 3f) / (Mathf.Pow(v, 3f) + Mathf.Pow(2.2f - 2.2f * v, 3f));
            }
        }

        grid = new Cell[size, size];
        for(int y = 0; y < size; y++) {
            for(int x = 0; x < size; x++) {
                float noiseValue = noiseMap[x, y];
                noiseValue -= falloffMap[x, y];
                bool isWater = noiseValue < waterLevel;
                Cell cell = new Cell(isWater);
                grid[x, y] = cell;
            }
        }
    }

    void OnDrawGizmos() {
        if(!Application.isPlaying) return;
        for(int y = 0; y < size; y++) {
            for(int x = 0; x < size; x++) {
                Cell cell = grid[x, y];
                if(cell.isWater)
                    Gizmos.color = Color.blue;
                else
                    Gizmos.color = Color.green;
                Vector3 pos = new Vector3(x, 0, y);
                Gizmos.DrawCube(pos, Vector3.one);
            }
        }
    }
}