材质还是要开启enable instance，这是上一次的写法
https://dbbh666.blog.csdn.net/article/details/136644181
最近发现更适合我个人的习惯的写法
就是代码控制这个整个过程
C#代码是这样的，获取一个mesh，获取每个mesh的transform，核心就完了，我这里是场景里的cube的mesh取来直接使用

using UnityEngine;

public class DrawMeshInstancedDemo : MonoBehaviour
{
    
    // Material to use for drawing the meshes.
    public Material material;

    private Matrix4x4[] matrices;
    //private MaterialPropertyBlock block;

    private Mesh mesh;

    private void Setup()
    {
        float range = 100.0f;
        int population = 1023;
        //Mesh mesh = CreateQuad();
        GameObject gameObject = GameObject.Find("Cube");
        MeshFilter mf = gameObject.GetComponent<MeshFilter>();
        this.mesh = mf.mesh;

        matrices = new Matrix4x4[population];
        //Vector4[] colors = new Vector4[population];

        //block = new MaterialPropertyBlock();

        for (int i = 0; i < population; i++)
        {
            Vector3 position = new Vector3(Random.Range(-range, range), Random.Range(-range, range), Random.Range(-range, range));
            Quaternion rotation = Quaternion.Euler(Random.Range(-180, 180), Random.Range(-180, 180), Random.Range(-180, 180));
            Vector3 scale = Vector3.one;


            matrices[i] = Matrix4x4.TRS(position, rotation, scale); 

        }

        // Custom shader needed to read these!!
        //block.SetVectorArray("_Colors", colors);
    }

    private void Start()
    {
        Setup();
    }

    private void Update()
    {
        // Draw a bunch of meshes each frame.
        Graphics.DrawMeshInstanced(mesh, 0, material, matrices, 1023 /*block*/);
    }
}

然后就是shader，有几点要注意的
pragma这里有个#pragma multi_compile_instancing
宏有这几个
UNITY_VERTEX_INPUT_INSTANCE_ID
UNITY_SETUP_INSTANCE_ID(i)
#ifdef UNITY_INSTANCING_ENABLED //o.color = _Colors[instanceID];
#endif
这几个宏，都要放在对的位置，才能获取正确的变量
`Shader “Unlit/instance”
{
Properties
{
_MainTex (“Texture”, 2D) = “white” {}
}
SubShader
{
Tags { “RenderType”=“Opaque” }
LOD 100

    Pass
    {
        CGPROGRAM
        #pragma vertex vert
        #pragma fragment frag
        #pragma multi_compile_instancing
        // make fog work
        //#pragma multi_compile_fog

        #include "UnityCG.cginc"

        struct appdata_t
        {
            float4 vertex : POSITION;
            float2 uv : TEXCOORD0;
            UNITY_VERTEX_INPUT_INSTANCE_ID
        };

        struct v2f
        {
            float2 uv : TEXCOORD0;
            //UNITY_FOG_COORDS(1)
            float4 vertex : SV_POSITION;
        };
        // float4 _Colors[1023];   // Max instanced batch size.
        sampler2D _MainTex;
        float4 _MainTex_ST;

        v2f vert(appdata_t i, uint instanceID: SV_InstanceID) {
         // Allow instancing.
         UNITY_SETUP_INSTANCE_ID(i);

         v2f o;
         //UNITY_TRANSFER_FOG(o,o.vertex);
         o.vertex = UnityObjectToClipPos(i.vertex);
         o.uv = i.uv;

         // If instancing on (it should be) assign per-instance color.
         #ifdef UNITY_INSTANCING_ENABLED //o.color = _Colors[instanceID];
         #endif
         return o;
         }

        fixed4 frag (v2f i) : SV_Target
        {
            // sample the texture
            fixed4 col = tex2D(_MainTex, i.uv);
            // apply fog
        //    UNITY_APPLY_FOG(i.fogCoord, col);
        col.gb=fixed2(0.2,0.2);
            return col;
        }
        ENDCG
    }
}

}
`
这样创建一个空对象，把C#脚本挂上去即可
看效果，最中间那个是原始cube，其他的都是instance搞出来的
需要注意的地方是1023这个事情，可能用纹理可以绕过去