Graphics.DrawMeshInstancedIndirect

参数

描述

This function is now obsolete. Use Graphics.RenderMeshIndirect instead. Draws the same mesh multiple times using GPU instancing.

This function only works on platforms that support compute shaders.

类似于 Graphics.DrawMeshInstanced，此函数用于绘制同一网格的多个实例，但与之不同的是，此函数中代表要绘制实例数的参数来自 /bufferWithArgs/。

如果您需要使用实例化的着色器多次绘制同一网格，则可以使用该函数。这些网格不会被视锥体或烘焙遮挡物做进一步的剔除处理，也不进行排序以提高透明度或 Z 效率。

带参数的缓冲区 bufferWithArgs 必须在给定的 argsOffset 偏移处具有五个整数： 每个实例的索引数、实例数、起始索引位置、基顶点位置、起始实例位置。

仅当网格中的子网格具有不同拓扑（例如，三角形和线条）时，Unity 才需要 submeshIndex 参数。否则，有关要绘制哪个子网格的所有信息都将来自 bufferWithArgs 参数。

下面是一个可用于绘制同一网格的多个实例的脚本：

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    public int instanceCount = 100000;
    public Mesh instanceMesh;
    public Material instanceMaterial;
    public int subMeshIndex = 0;

    private int cachedInstanceCount = -1;
    private int cachedSubMeshIndex = -1;
    private ComputeBuffer positionBuffer;
    private ComputeBuffer argsBuffer;
    private uint[] args = new uint[5] { 0, 0, 0, 0, 0 };

    void Start() {
        argsBuffer = new ComputeBuffer(1, args.Length * sizeof(uint), ComputeBufferType.IndirectArguments);
        UpdateBuffers();
    }

    void Update() {
        // Update starting position buffer
        if (cachedInstanceCount != instanceCount || cachedSubMeshIndex != subMeshIndex)
            UpdateBuffers();

        // Pad input
        if (Input.GetAxisRaw("Horizontal") != 0.0f)
            instanceCount = (int)Mathf.Clamp(instanceCount + Input.GetAxis("Horizontal") * 40000, 1.0f, 5000000.0f);

        // Render
        Graphics.DrawMeshInstancedIndirect(instanceMesh, subMeshIndex, instanceMaterial, new Bounds(Vector3.zero, new Vector3(100.0f, 100.0f, 100.0f)), argsBuffer);
    }

    void OnGUI() {
        GUI.Label(new Rect(265, 25, 200, 30), "Instance Count: " + instanceCount.ToString());
        instanceCount = (int)GUI.HorizontalSlider(new Rect(25, 20, 200, 30), (float)instanceCount, 1.0f, 5000000.0f);
    }

    void UpdateBuffers() {
        // Ensure submesh index is in range
        if (instanceMesh != null)
            subMeshIndex = Mathf.Clamp(subMeshIndex, 0, instanceMesh.subMeshCount - 1);

        // Positions
        if (positionBuffer != null)
            positionBuffer.Release();
        positionBuffer = new ComputeBuffer(instanceCount, 16);
        Vector4[] positions = new Vector4[instanceCount];
        for (int i = 0; i < instanceCount; i++) {
            float angle = Random.Range(0.0f, Mathf.PI * 2.0f);
            float distance = Random.Range(20.0f, 100.0f);
            float height = Random.Range(-2.0f, 2.0f);
            float size = Random.Range(0.05f, 0.25f);
            positions[i] = new Vector4(Mathf.Sin(angle) * distance, height, Mathf.Cos(angle) * distance, size);
        }
        positionBuffer.SetData(positions);
        instanceMaterial.SetBuffer("positionBuffer", positionBuffer);

        // Indirect args
        if (instanceMesh != null) {
            args[0] = (uint)instanceMesh.GetIndexCount(subMeshIndex);
            args[1] = (uint)instanceCount;
            args[2] = (uint)instanceMesh.GetIndexStart(subMeshIndex);
            args[3] = (uint)instanceMesh.GetBaseVertex(subMeshIndex);
        }
        else
        {
            args[0] = args[1] = args[2] = args[3] = 0;
        }
        argsBuffer.SetData(args);

        cachedInstanceCount = instanceCount;
        cachedSubMeshIndex = subMeshIndex;
    }

    void OnDisable() {
        if (positionBuffer != null)
            positionBuffer.Release();
        positionBuffer = null;

        if (argsBuffer != null)
            argsBuffer.Release();
        argsBuffer = null;
    }
}

下面是一个表面着色器，可以与上面的示例脚本配合使用：

          Shader "Instanced/InstancedSurfaceShader" {
    Properties {
        _MainTex ("Albedo (RGB)", 2D) = "white" {}
        _Glossiness ("Smoothness", Range(0,1)) = 0.5
        _Metallic ("Metallic", Range(0,1)) = 0.0
    }
    SubShader {
        Tags { "RenderType"="Opaque" }
        LOD 200

        CGPROGRAM
        // Physically based Standard lighting model
        #pragma surface surf Standard addshadow fullforwardshadows
        #pragma multi_compile_instancing
        #pragma instancing_options procedural:setup

        sampler2D _MainTex;

        struct Input {
            float2 uv_MainTex;
        };

    #ifdef UNITY_PROCEDURAL_INSTANCING_ENABLED
        StructuredBuffer<float4> positionBuffer;
    #endif

        void rotate2D(inout float2 v, float r)
        {
            float s, c;
            sincos(r, s, c);
            v = float2(v.x * c - v.y * s, v.x * s + v.y * c);
        }

        void setup()
        {
        #ifdef UNITY_PROCEDURAL_INSTANCING_ENABLED
            float4 data = positionBuffer[unity_InstanceID];

            float rotation = data.w * data.w * _Time.y * 0.5f;
            rotate2D(data.xz, rotation);

            unity_ObjectToWorld._11_21_31_41 = float4(data.w, 0, 0, 0);
            unity_ObjectToWorld._12_22_32_42 = float4(0, data.w, 0, 0);
            unity_ObjectToWorld._13_23_33_43 = float4(0, 0, data.w, 0);
            unity_ObjectToWorld._14_24_34_44 = float4(data.xyz, 1);
            unity_WorldToObject = unity_ObjectToWorld;
            unity_WorldToObject._14_24_34 *= -1;
            unity_WorldToObject._11_22_33 = 1.0f / unity_WorldToObject._11_22_33;
        #endif
        }

        half _Glossiness;
        half _Metallic;

        void surf (Input IN, inout SurfaceOutputStandard o) {
            fixed4 c = tex2D (_MainTex, IN.uv_MainTex);
            o.Albedo = c.rgb;
            o.Metallic = _Metallic;
            o.Smoothness = _Glossiness;
            o.Alpha = c.a;
        }
        ENDCG
    }
    FallBack "Diffuse"
}

下面是一个自定义着色器，可以与上面的示例脚本配合使用：

          Shader "Instanced/InstancedShader" {
    Properties {
        _MainTex ("Albedo (RGB)", 2D) = "white" {}
    }
    SubShader {

        Pass {

            Tags {"LightMode"="ForwardBase"}

            CGPROGRAM

            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile_fwdbase nolightmap nodirlightmap nodynlightmap novertexlight
            #pragma target 4.5

            #include "UnityCG.cginc"
            #include "UnityLightingCommon.cginc"
            #include "AutoLight.cginc"

            sampler2D _MainTex;

        #if SHADER_TARGET >= 45
            StructuredBuffer<float4> positionBuffer;
        #endif

            struct v2f
            {
                float4 pos : SV_POSITION;
                float2 uv_MainTex : TEXCOORD0;
                float3 ambient : TEXCOORD1;
                float3 diffuse : TEXCOORD2;
                float3 color : TEXCOORD3;
                SHADOW_COORDS(4)
            };

            void rotate2D(inout float2 v, float r)
            {
                float s, c;
                sincos(r, s, c);
                v = float2(v.x * c - v.y * s, v.x * s + v.y * c);
            }

            v2f vert (appdata_full v, uint instanceID : SV_InstanceID)
            {
            #if SHADER_TARGET >= 45
                float4 data = positionBuffer[instanceID];
            #else
                float4 data = 0;
            #endif

                float rotation = data.w * data.w * _Time.x * 0.5f;
                rotate2D(data.xz, rotation);

                float3 localPosition = v.vertex.xyz * data.w;
                float3 worldPosition = data.xyz + localPosition;
                float3 worldNormal = v.normal;



                float3 ndotl = saturate(dot(worldNormal, _WorldSpaceLightPos0.xyz));
                float3 ambient = ShadeSH9(float4(worldNormal, 1.0f));
                float3 diffuse = (ndotl * _LightColor0.rgb);
                float3 color = v.color;

                v2f o;
                o.pos = mul(UNITY_MATRIX_VP, float4(worldPosition, 1.0f));
                o.uv_MainTex = v.texcoord;
                o.ambient = ambient;
                o.diffuse = diffuse;
                o.color = color;
                TRANSFER_SHADOW(o)
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                fixed shadow = SHADOW_ATTENUATION(i);
                fixed4 albedo = tex2D(_MainTex, i.uv_MainTex);
                float3 lighting = i.diffuse * shadow + i.ambient;
                fixed4 output = fixed4(albedo.rgb * i.color * lighting, albedo.w);
                UNITY_APPLY_FOG(i.fogCoord, output);
                return output;
            }

            ENDCG
        }
    }
}