[知乎转载]Unity实现Minecraft（一）（二）

常规
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转载自 Cat Nine 的
Unity实现Minecraft(二)——优化原理 - 知乎 (zhihu.com)(Unity实现Minecraft(一)——原理介绍 - 知乎)

最近专门研究了下程序化生成地形，其中最典型的莫过于Minecraft中的地形生成，于是打算自己实现一下。闲话少说，游戏引擎：（2021.2) 。

①先来简单介绍原理：利用一个二重循环生成一个网格地图，然后对于每一个网格的位置坐标生成一个噪声值（噪声值介于0和1之间）,然后乘以一个自己定义的高度值Height,就会得到一个(0,Height)的值；然后再用一个循环从0到Height,每个高度放置方块即可。

注意：我们规定每一个单位的方块叫Block,后面也可以叫它体素（Voxel）。

②在Unity模拟一下过程：

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

namespace Test

{

public class ProceduralTerrain : MonoBehaviour

{

        [SerializeField] private float noiseScale = 0.05f;

        [SerializeField] private int worldSize = 6;

        [SerializeField] private int worldHeight = 10;

        [SerializeField] private int waterHeight = 4;

//用于保存每个Block类型的颜色

        private Dictionary<t_BlockType, Color> colorDic = new Dictionary<t_BlockType, Color>();


    <span class="k">private</span> <span class="k">void</span> <span class="n">Awake</span><span class="p">()</span>
    <span class="p">{</span>
        <span class="c1">//将Block的材质和颜色一一对应



            colorDic.Add(t_BlockType.Grass_Dirt, Color.green);//草方块对应绿色

            colorDic.Add(t_BlockType.Dirt, Color.yellow);//泥土对应黄色

            colorDic.Add(t_BlockType.Water, Color.blue);//水对应蓝色

            colorDic.Add(t_BlockType.Sand, Color.gray);//沙对应灰色

        }

private void Start()

{

GenerateTerrainData();


    <span class="p">}</span>
    <span class="k">private</span> <span class="n">List</span><span class="p">&lt;</span><span class="n">t_BlockData</span><span class="p">&gt;</span> <span class="n">worldBlockData</span> <span class="p">=</span> <span class="k">new</span> <span class="n">List</span><span class="p">&lt;</span><span class="n">t_BlockData</span><span class="p">&gt;();</span>
    <span class="c1">//生成地形所需数据，就是求出一个每个坐标的高度值



        void GenerateTerrainData()

{

t_BlockType blockType;

for (int i = 0; i < worldSize; i++)

{

for (int j = 0; j < worldSize; j++)

{

float noiseValue = Mathf.PerlinNoise((transform.position.x + i)  noiseScale, (transform.position.z + j)  noiseScale);

int groundPosition = Mathf.RoundToInt(noiseValue * worldHeight);

for (int y = 0; y < worldHeight; y++)

{

blockType = t_BlockType.Dirt;

if (y > groundPosition)

{

if (y < waterHeight)

{

blockType = t_BlockType.Water;

}

else

{

blockType = t_BlockType.Air;

}


                    <span class="p">}</span>
                    <span class="k">else</span> <span class="k">if</span> <span class="p">(</span><span class="n">y</span> <span class="p">==</span> <span class="n">groundPosition</span> <span class="p">&amp;&amp;</span> <span class="n">y</span> <span class="p">&lt;</span> <span class="n">waterHeight</span><span class="p">)</span>
                    <span class="p">{</span>
                        <span class="n">blockType</span> <span class="p">=</span> <span class="n">t_BlockType</span><span class="p">.</span><span class="n">Sand</span><span class="p">;</span>
                    <span class="p">}</span>
                    <span class="k">else</span> <span class="k">if</span> <span class="p">(</span><span class="n">y</span> <span class="p">==</span> <span class="n">groundPosition</span><span class="p">)</span>
                    <span class="p">{</span>
                        <span class="n">blockType</span> <span class="p">=</span> <span class="n">t_BlockType</span><span class="p">.</span><span class="n">Grass_Dirt</span><span class="p">;</span>
                    <span class="p">}</span>

                    <span class="n">t_BlockData</span> <span class="n">temp</span> <span class="p">=</span> <span class="k">new</span> <span class="n">t_BlockData</span><span class="p">(</span><span class="k">new</span> <span class="n">Vector3</span><span class="p">(</span><span class="n">transform</span><span class="p">.</span><span class="n">position</span><span class="p">.</span><span class="n">x</span> <span class="p">+</span> <span class="n">i</span><span class="p">,</span> <span class="n">y</span><span class="p">,</span> <span class="n">transform</span><span class="p">.</span><span class="n">position</span><span class="p">.</span><span class="n">z</span> <span class="p">+</span> <span class="n">j</span><span class="p">),</span> <span class="n">blockType</span><span class="p">);</span>
                    <span class="n">worldBlockData</span><span class="p">.</span><span class="n">Add</span><span class="p">(</span><span class="n">temp</span><span class="p">);</span>
                <span class="p">}</span>
            <span class="p">}</span>
        <span class="p">}</span>
    <span class="p">}</span>
    <span class="c1">//用Gizmos来模拟生成的地形



        private void OnDrawGizmos()

{

if (worldBlockData.Count > 0)

{

foreach (var block in worldBlockData)

{

if (block.blockType == t_BlockType.Air)

{

continue;

}

Gizmos.color = colorDic[block.blockType];

Gizmos.DrawCube(block.blockPosition,new Vector3(1f,1f,1f));

}

}


    <span class="p">}</span>
<span class="p">}</span>

<span class="k">internal</span> <span class="k">class</span> <span class="nc">t_BlockData</span>
<span class="p">{</span>
    <span class="k">public</span> <span class="n">Vector3</span> <span class="n">blockPosition</span><span class="p">;</span>
    <span class="k">public</span> <span class="n">t_BlockType</span> <span class="n">blockType</span><span class="p">;</span>

    <span class="k">public</span> <span class="n">t_BlockData</span><span class="p">(</span><span class="n">Vector3</span> <span class="n">position</span><span class="p">,</span><span class="n">t_BlockType</span> <span class="n">type</span><span class="p">)</span>
    <span class="p">{</span>
        <span class="n">blockPosition</span> <span class="p">=</span> <span class="n">position</span><span class="p">;</span>
        <span class="n">blockType</span> <span class="p">=</span> <span class="n">type</span><span class="p">;</span>
    <span class="p">}</span>
<span class="p">}</span>
<span class="k">internal</span> <span class="k">enum</span> <span class="n">t_BlockType</span>
<span class="p">{</span>
    <span class="n">None</span><span class="p">,</span>
    <span class="n">Air</span><span class="p">,</span>
    <span class="n">Grass_Dirt</span><span class="p">,</span>
    <span class="n">Dirt</span><span class="p">,</span>
    <span class="n">Sand</span><span class="p">,</span>
    <span class="n">Water</span>
<span class="p">};</span>



}
v2-93248e8ceac920a7af8db7c85e718cfa_b.jpg720×238 16.4 KB
v2-13f991c9f9f14ba90edcbf6f19c0d41b_b.jpg720×335 18 KB

③总结：这样就简单完成了一个模拟过程，但这样有一个很明显的问题，一旦我们的地形过大就会导致游戏帧率下降，影响游戏体验，所以我们就来讲讲真正的Minecraft地形实现是从哪些方面来进行优化。

接上一篇文章，我们讲述了Minecraft地形生成原理，并在Unity中简单实现了出来。但我们可以看出这样的地形存在很多不必要的Block,我们在Minecraft中根本不会看到那些地面以下的Block,也就是只渲染那些我们玩家能够看到的那些处于地面上的Block,像下面这张图一样：

v2-213d4923dcc6bd4dabffc7baf2d29ea7_b.jpg720×327 26.7 KB

当然，不渲染不代表它不存在，我们仍然需要保留其数据。也就我们需要维护两个List，一个存放每个Block的数据(包括位置信息，Block类型等)，另一个就是存放真正需要被渲染的Block的实体。（为了保证游戏的拓展性，我们需要将数据和渲染相分离，这样也是为了游戏性能更好，详细说明后面也会讲到）对于那些不需要在开始被渲染的Block，我们只是将其数据保存，以便后序需要渲染它时才把它渲染出来。

细心的读者可能会发现，上面那张图片还有一个神奇之处：

v2-a1c407ff58d81180e720c02c3d8abb71_b.jpg720×351 24.9 KB

地面上的Block也应该是一个完整的方块，为什么它的有些面没了。这是因为游戏为了性能的进一步提升，采用了面优化技术。就是将某些玩家永远看不见的面给剔除，这里简单介绍一下在游戏中如何实现面优化：我们知道在Unity中，一个面由2个三角面构成，这两个三角面又是4个顶点的组合按照左手螺旋的顺序来构成的。所以要想单独渲染一个面，我们就得提供顶点和三角形。所以我们实现Minecraft的地形时采用的动态Mesh生成，而不是把方块做成Prefab,然后实例化。针对不需要渲染的面，我们就不给它提供顶点或者三角面即可。（建议读者可以去了解下Unity中的Mesh）

下篇文章就正式开始制作我们的Minecraft了。

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