Grid_part2.cs

using UnityEngine;
using System.Collections.Generic;

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;
            }
        }

        DrawTerrainMesh(grid);
    }

    void DrawTerrainMesh(Cell[,] grid) {
        Mesh mesh = new Mesh();
        List<Vector3> vertices = new List<Vector3>();
        List<int> triangles = new List<int>();
        List<Vector2> uvs = new List<Vector2>();
        for(int y = 0; y < size; y++) {
            for(int x = 0; x < size; x++) {
                Cell cell = grid[x, y];
                if(!cell.isWater) {
                    Vector3 a = new Vector3(x - .5f, 0, y + .5f);
                    Vector3 b = new Vector3(x + .5f, 0, y + .5f);
                    Vector3 c = new Vector3(x - .5f, 0, y - .5f);
                    Vector3 d = new Vector3(x + .5f, 0, y - .5f);
                    Vector2 uvA = new Vector2(x / (float)size, y / (float)size);
                    Vector2 uvB = new Vector2((x + 1) / (float)size, y / (float)size);
                    Vector2 uvC = new Vector2(x / (float)size, (y + 1) / (float)size);
                    Vector2 uvD = new Vector2((x + 1) / (float)size, (y + 1) / (float)size);
                    Vector3[] v = new Vector3[] { a, b, c, b, d, c };
                    Vector2[] uv = new Vector2[] { uvA, uvB, uvC, uvB, uvD, uvC };
                    for(int k = 0; k < 6; k++) {
                        vertices.Add(v[k]);
                        triangles.Add(triangles.Count);
                        uvs.Add(uv[k]);
                    }
                }
            }
        }
        mesh.vertices = vertices.ToArray();
        mesh.triangles = triangles.ToArray();
        mesh.uv = uvs.ToArray();
        mesh.RecalculateNormals();

        MeshFilter meshFilter = gameObject.AddComponent<MeshFilter>();
        meshFilter.mesh = mesh;

        MeshRenderer meshRenderer = gameObject.AddComponent<MeshRenderer>();
    }

    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);
            }
        }
    }
}