DrawMeshInstancedIndirect Example Comments and Questions

Unity Engine
34

I think this demonstrates the point. Can anyone spot any obvious mistakes and/or is it reproducible on other systems?

It follows the pattern of the example if you want to try it for yourselves.

With iArgOffset set to 0, I expect to see a green and red mesh, set to 1 a green and cyan mesh if unityInstanceID is behaving as expected but I actually get green and red in both cases.

TestBehaviourScript.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class TestBehaviourScript : MonoBehaviour {
    public Mesh instanceMesh;
    public Material instanceMaterial;
    public int iArgOffset = 0;

    private ComputeBuffer argsBuffer;
    private uint[] args = new uint[5] { 0, 0, 0, 0, 0 };

    // Use this for initialization
    void Start () {

        argsBuffer = new ComputeBuffer(2, args.Length * sizeof(uint), ComputeBufferType.IndirectArguments);
        UpdateBuffers();
    }

    // Update is called once per frame
    void Update () {

        int argsOffset = iArgOffset * 4 * 5;
        Graphics.DrawMeshInstancedIndirect(instanceMesh, 0, instanceMaterial, new Bounds(Vector3.zero, new Vector3(10000.0f, 10000.0f, 10000.0f)), argsBuffer, argsOffset);

    }

    void UpdateBuffers()
    {

        uint[] argssum = new uint[2 * 5];

        // indirect args
        uint numIndices = (instanceMesh != null) ? (uint)instanceMesh.GetIndexCount(0) : 0;
        argssum[0] = numIndices;
        argssum[1] = 2;
        argssum[2] = 0;
        argssum[3] = 0;
        argssum[4] = 0;
        argssum[5] = numIndices;
        argssum[6] = 2;
        argssum[7] = 0;
        argssum[8] = 0;
        argssum[9] = 1;

        argsBuffer.SetData(argssum);

    }

    void OnDisable()
    {

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

}

TestInstancedSurfaceShader.shader

Shader "Instanced/TestInstancedSurfaceShader" {
    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
#pragma multi_compile_instancing
#pragma instancing_options procedural:setup

        sampler2D _MainTex;
    float4 col;
    struct Input {
        float2 uv_MainTex;
    };

#ifdef UNITY_PROCEDURAL_INSTANCING_ENABLED

#endif




    void setup()
    {
#ifdef UNITY_PROCEDURAL_INSTANCING_ENABLED

        col = float4(0, 0, 1, 1.0);

        if (unity_InstanceID == 0)
        {
            col = float4(1, 0, 0, 1.0);
            unity_ObjectToWorld._14_24_34_44 = float4(0, 1, 4, 1.0f);
        }
        else if (unity_InstanceID == 1)
        {
            col = float4(0, 1, 0, 1.0);
            unity_ObjectToWorld._14_24_34_44 = float4(1.5, 1, 4, 1.0f);
        }
        else
        {
            col = float4(0, 1, 1, 1.0);
            unity_ObjectToWorld._14_24_34_44 = float4(-1.5, 1, 4, 1.0f);
        }


        unity_ObjectToWorld._11_21_31_41 = float4(1, 0, 0, 0.0f);
        unity_ObjectToWorld._12_22_32_42 = float4(0, 1, 0, 0.0f);
        unity_ObjectToWorld._13_23_33_43 = float4(0, 0, 1, 0.0f);

        float3x3 w2oRotation;
        w2oRotation[0] = unity_ObjectToWorld[1].yzx * unity_ObjectToWorld[2].zxy - unity_ObjectToWorld[1].zxy * unity_ObjectToWorld[2].yzx;
        w2oRotation[1] = unity_ObjectToWorld[0].zxy * unity_ObjectToWorld[2].yzx - unity_ObjectToWorld[0].yzx * unity_ObjectToWorld[2].zxy;
        w2oRotation[2] = unity_ObjectToWorld[0].yzx * unity_ObjectToWorld[1].zxy - unity_ObjectToWorld[0].zxy * unity_ObjectToWorld[1].yzx;
        float det = dot(unity_ObjectToWorld[0], w2oRotation[0]);
        w2oRotation = transpose(w2oRotation);
        w2oRotation *= rcp(det);

        float3 w2oPosition = mul(w2oRotation, -unity_ObjectToWorld._14_24_34);

        unity_WorldToObject._11_21_31_41 = float4(w2oRotation._11_21_31, 0.0f);
        unity_WorldToObject._12_22_32_42 = float4(w2oRotation._12_22_32, 0.0f);
        unity_WorldToObject._13_23_33_43 = float4(w2oRotation._13_23_33, 0.0f);  
        unity_WorldToObject._14_24_34_44 = float4(w2oPosition, 1.0f);

#endif
    }

    half _Glossiness;
    half _Metallic;


    void surf(Input IN, inout SurfaceOutputStandard o) {
        fixed4 c = tex2D(_MainTex, IN.uv_MainTex);
        o.Albedo = col.rgb;
        o.Metallic = _Metallic;
        o.Smoothness = _Glossiness;
        o.Alpha = 1.0f;
    }
    ENDCG
    }
        FallBack "Diffuse"
}
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