Graphics.RenderPrimitivesIndexedIndirect

参数

描述

使用 GPU 实例化和来自 commandBuffer 的渲染命令参数，通过自定义着色器渲染索引图元。

此函数允许您从 GPU 控制渲染命令参数，以渲染给定数量的索引图元和实例。使用 RenderParams.worldBounds 定义边界，以剔除和对使用此方法作为单个实体渲染的几何体进行排序。

此函数仅在支持 计算着色器 的平台上有效。

在着色器的传递部分添加以下行，以访问 UnityIndirect.cginc 中指定的命令、实例和顶点 ID：A: RenderMeshIndirect。

#define UNITY_INDIRECT_DRAW_ARGS IndirectDrawIndexedArgs
#include "UnityIndirect.cginc"

在着色器函数开头添加以下行，以设置 ID 访问函数

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

以下示例执行两个间接渲染命令。每个渲染命令都渲染 10 个网格实例。关联的材质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.IndirectDrawIndexedArgs[] 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.IndirectDrawIndexedArgs.size);
        commandData = new GraphicsBuffer.IndirectDrawIndexedArgs[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.SetMatrix("_ObjectToWorld", Matrix4x4.Translate(new Vector3(-4.5f, 0, 0)));
        commandData[0].indexCountPerInstance = mesh.GetIndexCount(0);
        commandData[0].baseVertexIndex = mesh.GetBaseVertex(0);
        commandData[0].startIndex = mesh.GetIndexStart(0);
        commandData[0].instanceCount = 10;
        commandData[1].indexCountPerInstance = mesh.GetIndexCount(0);
        commandData[1].baseVertexIndex = mesh.GetBaseVertex(0);
        commandData[1].startIndex = mesh.GetIndexStart(0);
        commandData[1].instanceCount = 10;
        commandBuf.SetData(commandData);
        Graphics.RenderPrimitivesIndexedIndirect(rp, MeshTopology.Triangles, meshTriangles, commandBuf, commandCount);
    }
}

将以下示例着色器与上面的 C# 示例代码一起使用

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

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

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

            StructuredBuffer<float3> _Positions;
            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[GetIndirectVertexID(svVertexID)];
                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
        }
    }
}