Graphics.RenderPrimitivesIndirect

参数

说明

利用 commandBuffer 中的渲染命令参数，使用 GPU 实例化和自定义着色器渲染图元。

此函数提供一种方法，可从 GPU 控制渲染命令参数，以渲染给定数量的图元和实例。使用 RenderParams.worldBounds，定义边界以剔除和对采用该方法渲染的几何体进行排序，使其成为一个单一实体。

此函数仅适用于支持 计算着色器 的平台。

根据 UnityIndirect.cginc 中的规定，将以下行添加到着色器的 pass 部分，以访问命令、实例和顶点 ID：其他资源：RenderMeshIndirect。

#define UNITY_INDIRECT_DRAW_ARGS IndirectDrawArgs
#include "UnityIndirect.cginc"

将以下行添加到着色器函数开头，以设置 ID 访问函数

InitIndirectDrawArgs(0); // pass SV_DrawID semantic value here for multi-draw support

下列示例执行两条间接呈现命令。每条命令呈现 10 个 Mesh 实例。关联的 Material 必须使用以下自定义着色器

using UnityEngine;

public class ExampleClass : MonoBehaviour
{
    public Material material;
    public Mesh mesh;

    GraphicsBuffer meshTriangles;
    GraphicsBuffer meshPositions;
    GraphicsBuffer commandBuf;
    GraphicsBuffer.IndirectDrawArgs[] commandData;
    const int commandCount = 2;

    void Start()
    {
        // note: remember to check "Read/Write" on the mesh asset to get access to the geometry data
        meshTriangles = new GraphicsBuffer(GraphicsBuffer.Target.Structured, mesh.triangles.Length, sizeof(int));
        meshTriangles.SetData(mesh.triangles);
        meshPositions = new GraphicsBuffer(GraphicsBuffer.Target.Structured, mesh.vertices.Length, 3 * sizeof(float));
        meshPositions.SetData(mesh.vertices);
        commandBuf = new GraphicsBuffer(GraphicsBuffer.Target.IndirectArguments, commandCount, GraphicsBuffer.IndirectDrawArgs.size);
        commandData = new GraphicsBuffer.IndirectDrawArgs[commandCount];
    }

    void OnDestroy()
    {
        meshTriangles?.Dispose();
        meshTriangles = null;
        meshPositions?.Dispose();
        meshPositions = null;
        commandBuf?.Dispose();
        commandBuf = null;
    }

    void Update()
    {
        RenderParams rp = new RenderParams(material);
        rp.worldBounds = new Bounds(Vector3.zero, 10000*Vector3.one); // use tighter bounds
        rp.matProps = new MaterialPropertyBlock();
        rp.matProps.SetBuffer("_Triangles", meshTriangles);
        rp.matProps.SetBuffer("_Positions", meshPositions);
        rp.matProps.SetInt("_BaseVertexIndex", (int)mesh.GetBaseVertex(0));
        rp.matProps.SetMatrix("_ObjectToWorld", Matrix4x4.Translate(new Vector3(-4.5f, 0, 0)));
        commandData[0].vertexCountPerInstance = mesh.GetIndexCount(0);
        commandData[0].instanceCount = 10;
        commandData[1].vertexCountPerInstance = mesh.GetIndexCount(0);
        commandData[1].instanceCount = 10;
        commandBuf.SetData(commandData);
        Graphics.RenderPrimitivesIndirect(rp, MeshTopology.Triangles, commandBuf, commandCount);
    }
}

将以下示例着色器用于上述 C# 示例代码

          Shader "ExampleShader"
{
    SubShader
    {
        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"
            #define UNITY_INDIRECT_DRAW_ARGS IndirectDrawArgs
            #include "UnityIndirect.cginc"

            struct v2f
            {
                float4 pos : SV_POSITION;
                float4 color : COLOR0;
            };

            StructuredBuffer<int> _Triangles;
            StructuredBuffer<float3> _Positions;
            uniform uint _BaseVertexIndex;
            uniform float4x4 _ObjectToWorld;

            v2f vert(uint svVertexID: SV_VertexID, uint svInstanceID : SV_InstanceID)
            {
                InitIndirectDrawArgs(0);
                v2f o;
                uint cmdID = GetCommandID(0);
                uint instanceID = GetIndirectInstanceID(svInstanceID);
                float3 pos = _Positions[_Triangles[GetIndirectVertexID(svVertexID)] + _BaseVertexIndex];
                float4 wpos = mul(_ObjectToWorld, float4(pos + float3(instanceID, cmdID, 0.0f), 1.0f));
                o.pos = mul(UNITY_MATRIX_VP, wpos);
                o.color = float4(cmdID & 1 ? 0.0f : 1.0f, cmdID & 1 ? 1.0f : 0.0f, instanceID / float(GetIndirectInstanceCount()), 0.0f);
                return o;
            }

            float4 frag(v2f i) : SV_Target
            {
                return i.color;
            }
            ENDCG
        }
    }
}