[游戏随机生成地形] Meteorite Algorithm

梦里梦外; 2022-06-17 08:45 205阅读 0赞

### 懒得不想复习: ###

今天在尝试生成随机地形的时候, 想到了一个简单又比较实用的方法, 不知道是否有前辈已经用过, 我暂且将它命名  
**Meteorite Algorithm** (陨石算法)  
从名字就能猜出来, 这是个什么算法了hahahaha.

最终效果:  
![Random Island][]

### 具体思路: ###

1. 生成能存储高度的2维网格
    
    2. 初始化高度 (这一步可以影响最终地形效果)
    
    3. 在比网格稍大的区域内,随机扔下随机大小的陨石(不用扔真的陨石)(比网格稍大的区域: 原网格区域在四个方向 + 最大陨石半径), 陨石会在他的半径所及的圆形区域内削减地面高度, 陨坑中心的地面高度削减最多.
    
    4. 更新地图画面 (可以最后更新, 但是放到这里更刺激)
    
    5. 回到第三步,继续扔陨石

注意, 如果第二步的初始高度全部为一个常量, 则最终生成的地形较为零散. 所以可以考虑在初始化时将他中心升高, 最终会生成一个岛屿, 如上图.

### 代码: ###

暂且将我写的代码贴在下面, 代码丑陋之处还请指正.

// Meteorite Algorithm
    // Jamesika 2017/6/14
    using System.Collections;
    using System.Collections.Generic;
    using UnityEngine;
    using Random = UnityEngine.Random;
    
    public class MeteoriteAlgorithm : MonoBehaviour {
    
        //陨石坠落生成随机地形
        //陨石数量,陨石大小规模
        //地图范围
        //地图初始高度
        //海平面高度
    
        public GameObject landPrefab;
        public Sprite land;
        public Sprite water;
    
        [Header("是否生成主岛屿")]
        public bool mainIsland = true;
        [Header("主岛屿地形增加高度")]
        public float addHeight = 100f;
        [Header("陨石数目")]
        public int meteoNumber = 20;
        [Header("陨石大小")]
        public Vector2 meteoSize = new Vector2(3,30);
        [Header("地图大小")]
        public Vector2 mapSize = new Vector2 (50, 50);
        [Header("地面初始高度")]
        public float landHeight = 50f;
        [Header("海平面高度")]
        public float seaHeight = 0f;
    
        public float[][] map;//记录网格的高度
        private SpriteRenderer[][] sprites;//修改网格贴图
    
        void Start () 
        {
            StartCoroutine(GenerateLand ());
        }
        //由两个协程组成,先初始化数据,再模拟陨石
        IEnumerator GenerateLand()
        {
            yield return StartCoroutine(InitialLand ());
            yield return StartCoroutine(MeteoriteCrash ());
        }
        //初始化数据
        IEnumerator InitialLand()
        {
            map = new float[(int)mapSize.x][];
            sprites = new SpriteRenderer[(int)mapSize.x][];
            for (int i = 0; i < mapSize.x; i++) 
            {
                map [i] = new float[(int)mapSize.y];
                sprites [i] = new SpriteRenderer[(int)mapSize.y];
            }
    
            float halfDiagLine = Mathf.Sqrt (Mathf.Pow (mapSize.x / 2, 2) + Mathf.Pow (mapSize.y / 2, 2));
    
            for (int i = 0; i < mapSize.x; i++)
            {   for (int j = 0; j < mapSize.y; j++) 
                {
                    map [i] [j] = landHeight;
    
                    //越靠近中间的地方越高
                    if (mainIsland == true)
                        map [i] [j] += addHeight*(1-Mathf.Sqrt (Mathf.Pow (mapSize.x / 2 - i, 2) + Mathf.Pow (mapSize.y / 2 - j, 2)) / halfDiagLine);
    
                    sprites [i] [j] = (Instantiate (landPrefab, new Vector2 (i, j), Quaternion.identity) as GameObject).GetComponent<SpriteRenderer> ();
                    //如果计算超过 5000 次,就等待
                    if ((i+1)*(j+1) % 5000 == 0)
                        yield return null;
                }   
            }
    
            yield return FlashMap (true);
    
            yield return StartCoroutine(MeteoriteCrash ());
        }
        //模拟陨石撞击
        IEnumerator MeteoriteCrash()
        {
            //越大的陨石出现的几率越低
            //使用定义域为[0.5,10]的反比例函数来进行简单的概率分布
            Vector2 len = new Vector2(0.5f,10f);
            for (int count = 0; count < meteoNumber; count++) 
            {
                float valueRatio = (meteoSize.y - meteoSize.x)/(len.y-len.x);
                float randNum = Random.Range (len.x, len.y);
                float randRadius = (randNum - len.x) * valueRatio + meteoSize.x;
    
                float randX = Random.value * (mapSize.x+2*meteoSize.y) - meteoSize.y;
                float randY = Random.value * (mapSize.y+2*meteoSize.y)-meteoSize.y;
    
                for(int i=-(int)randRadius;i<=(int)randRadius;i++)
                    for(int j= -(int)randRadius;j<=(int)randRadius;j++)
                    {
                        float x = i + randX;
                        float y = j + randY;
                        if (x < 0 || x >= mapSize.x || y < 0 || y >= mapSize.y || i*i+j*j>=Mathf.Pow(randRadius,2)) 
                            continue;
                        map[(int)x][(int)y] -= Mathf.Sqrt(Mathf.Pow(randRadius,2) - i*i - j*j);
                    }
    
                yield return StartCoroutine (FlashMap (false,new Vector2 (randX - randRadius, randY + randRadius), new Vector2 (randX + randRadius, randY - randRadius)));
            }
    
        }
        //根据地形高度,改变贴图,flashAll指全部刷新,否则刷新两个坐标中间的网格贴图
        IEnumerator FlashMap(bool flashAll,Vector2 leftTop =  new Vector2(),Vector2 rightBottom = new Vector2())
        {
            //全部刷新
            if (flashAll) 
            {
                leftTop = new Vector2 (0, mapSize.y-1);
                rightBottom = new Vector2 (mapSize.x-1, 0);
            }
            //这里是小于等于,传入值的时候注意范围
            for (int i = (int)leftTop.x; i <= (int)rightBottom.x; i++) 
            {
                for (int j = (int)rightBottom.y; j <= (int)leftTop.y; j++) 
                {
                    if (i < 0 || j < 0 || i >= mapSize.x || j >= mapSize.y)
                        continue;
                    if (map [i] [j] <= seaHeight)
                        sprites [i] [j].sprite = water;
                    else
                        sprites [i] [j].sprite = land;
                    //加深颜色,只改变了前两个维度,即只加深了蓝绿色(更像地球)
                    float blackValue = Mathf.Clamp((map [i] [j] - seaHeight) / 255+0.8f,0,1);
                    sprites [i] [j].color = new Color(blackValue,blackValue,1,1);
                    if ((i+1)*(j+1) % 5000 == 0)
                        yield return null;
                }
            }
            yield return null;
        }
    }

### 更加厉害的生成地形的方法 ###

#### Amit 的多边形游戏地图生成: ####

> [https://www.indienova.com/indie-game-development/polygonal-map-generation-for-games-1/][https_www.indienova.com_indie-game-development_polygonal-map-generation-for-games-1]

#### 其他可能用到的方法: ####

分形
    元胞自动机
    柏林噪音
    ...

### 如果大家有什么好的方法生成地形请一起分享吧~ ###

减小陨石半径,增加陨石数量

![减小陨石半径,增大陨石数量][SouthEast]

进行适当参数调整(减小高度差),生成3D地形

![这里写图片描述][SouthEast 1]

[Random Island]: /images/20220617/847984ec63c5444b9f6b7c3d7aab4aac.png
[https_www.indienova.com_indie-game-development_polygonal-map-generation-for-games-1]: https://www.indienova.com/indie-game-development/polygonal-map-generation-for-games-1/
[SouthEast]: /images/20220617/4496992a3f9a4f0c8d5b54dfb3202bb6.png
[SouthEast 1]: /images/20220617/40f9f6438a9e45c5881021c4eb1c46f2.png