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Unity Engine

RenderPrimitivesIndirect(in RenderParams, MeshTopology, GraphicsBuffer, int, int)

Renders primitives with GPU instancing and a custom shader using rendering command arguments from argsBuffer.
Read time 3 minutesLast updated 6 days ago

Definition

  • Type: Method
  • Namespace: UnityEngine
  • Assembly: UnityEngine.CoreModule

RenderPrimitivesIndirect(RenderParams, MeshTopology, GraphicsBuffer, int, int)

public static void RenderPrimitivesIndirect(in RenderParams rparams, MeshTopology topology, GraphicsBuffer argsBuffer, int commandCount = 1, int startCommand = 0)

Parameters

rparams

RenderParams
The parameters Unity uses to render the primitives.

topology

MeshTopology
Primitive topology (for example, triangles or lines).

argsBuffer

GraphicsBuffer
A graphics buffer that provides rendering command arguments (see GraphicsBuffer.IndirectDrawArgs).

commandCount

int
The number of rendering commands to execute in the 
argsBuffer
.

startCommand

int
The first command to execute in the 
argsBuffer
.

Remarks

This function provides a way to control rendering command arguments from GPU to render a given number of primitives and instances. Use /RenderParams.worldBounds/ to define bounds to cull and sort the geometry rendered with the method as a single entity.
This function only works on platforms that support compute shaders.
Add the following lines in the pass section of a shader to access command, instance and vertex ID's as specified in UnityIndirect.cginc: Additional Resources: Graphics.RenderMeshIndirect.
#define UNITY_INDIRECT_DRAW_ARGS IndirectDrawArgs#include "UnityIndirect.cginc"
Add the following line to the beginning of a shader function to setup the ID access functions:
InitIndirectDrawArgs(0);
The following example executes two indirect rendering commands. Each command renders 10 Mesh instances. The associated Material must use the below custom shader:
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);    }}
Use the following example shader with the above C# example code:
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        }    }}