Question Nothing appearing while using DrawMeshInstancedIndirect, DrawMeshInstanced only partially working

I'm trying to draw stuff using DrawMeshInstancedIndirect, but absolutely nothing is appearing. I understand that DrawMeshInstanced supports up to 1023 instances, but when I use it it only draws up to a max of half of that.


Successfully drawing 400 red quads using DrawMeshInstanced. Virtually the same code will not draw anything using DrawMeshInstancedIndirect.

Things I've tried:

• I've gone through all the docs and tutorials I could find regarding this.
• "Enable GPU Instancing" is ticked on the material.
• This occurs using the built-in renderer in a new project (2020.3.0f1) with almost zero packages imported.
• I've double checked that the information in the buffers is correct, and the fact that DrawMeshInstanced works (kinda) implies that it is, too.
• It doesn't seem to make a difference whether I use a MaterialPropertyBlock or set the data right on the material. Likewise instantiating the material makes no difference.

I'll attach a minimal project here, but this is the relevant bit of C# (the bit that populates the buffer/shader data, and the update loop):

Code (CSharp):

1.  
2.     private void Init()
3.     {
4.         if (m_materialInstance)
5.             DestroyImmediate(m_materialInstance);
6.  
7.         m_materialInstance = new Material(m_material);
8.  
9.         m_indirectArgsBuffer?.Dispose();
10.         m_positionsBuffer?.Dispose();
11.  
12.         m_indirectArgsBuffer = new ComputeBuffer(5, sizeof(uint));
13.         m_positionsBuffer = new ComputeBuffer(m_count, sizeof(float) * 2);
14.  
15.         // set up the indirect args: [6, number of instances, 0, 0, 0]
16.         m_indirectArgs[0] = m_mesh.GetIndexCount(0);
17.         m_indirectArgs[1] = (uint)m_count;
18.         m_indirectArgs[2] = m_mesh.GetIndexStart(0);
19.         m_indirectArgs[3] = m_mesh.GetBaseVertex(0);
20.         m_indirectArgsBuffer.SetData(m_indirectArgs);
21.    
22.         // generate a grid of positions and send them to the buffer
23.         GenerateGridPositions();
24.         m_positionsBuffer.SetData(m_meshPositions);
25.    
26.         m_propertyBlock = new MaterialPropertyBlock();
27.         m_propertyBlock.SetBuffer(MATERIAL_BUFFER_PROPERTY, m_positionsBuffer);
28.         m_propertyBlock.SetFloat(SIZE_PROPERTY, m_size);
29.         m_propertyBlock.SetColor(COLOUR_PROPERTY, m_colour);
30.     }
31.  
32.     private void Update()
33.     {
34.         if (!m_materialInstance || !m_mesh)
35.             return;
36.    
37.         if (m_count != m_matrices.Length)
38.             Init();
39.    
40.         if (m_drawDirect)
41.         {
42.             Graphics.DrawMeshInstanced(m_mesh, 0, m_materialInstance, m_matrices, m_count, m_propertyBlock);
43.         }
44.  
45.         if (m_drawIndirect)
46.         {
47.             // indirect args buffer = [6, number of instances, 0, 0, 0]
48.             Graphics.DrawMeshInstancedIndirect(m_mesh, 0, m_materialInstance, m_bounds, m_indirectArgsBuffer, properties: m_propertyBlock, layer: gameObject.layer);
49.         }
50.     }
51.    

and the shader itself:

Code (CSharp):

1. Shader "Unlit/InstancedTestShader"
2. {
3.     SubShader
4.     {
5.         Pass
6.         {
7.             CGPROGRAM
8.             #pragma vertex vert
9.             #pragma fragment frag
10.             #pragma target 4.5
11.             #pragma multi_compile_instancing
12.  
13.             #include "UnityCG.cginc"
14.  
15.             float4 _Colour;
16.             float _Size;
17.             StructuredBuffer<float2> _PositionsBuffer;
18.  
19.             struct appdata
20.             {
21.                 UNITY_VERTEX_INPUT_INSTANCE_ID
22.                 float4 vertex : POSITION;
23.             };
24.  
25.             struct v2f
26.             {
27.                 float4 vertex : SV_POSITION;
28.             };
29.  
30.             v2f vert(appdata v, uint instanceID : SV_InstanceID)
31.             {
32.                 v2f o;
33.                 UNITY_SETUP_INSTANCE_ID(v);
34.  
35.                 float2 position = _PositionsBuffer[instanceID];
36.                 o.vertex = UnityObjectToClipPos(v.vertex * _Size + float3(position, 0.));
37.  
38.                 return o;
39.             }
40.  
41.             fixed4 frag(v2f i) : SV_Target
42.             {
43.                 return _Colour;
44.             }
45.  
46.             ENDCG
47.         }
48.     }
49. }
50.  

Please help me figure this out, it's driving me crazy! Again, the minimal reproduction project is also attached.

 

The matrix is missing, add a buffer to store matrices or rebuild it in shader.
For your example you can simply change the vertex out as

o.vertex = mul(UNITY_MATRIX_VP, float4(v.vertex * _Size + float3(position, 0.), 1.0));

 

Hm, that doesn't seem to work. Changing the line in the vertex shader just makes it so nothing renders at all.

Isn't the matrix multiplication already covered by UnityObjectToClipPos?

 

Sorry, I'm missing this line.

m_indirectArgsBuffer = new ComputeBuffer(5, sizeof(uint), ComputeBufferType.IndirectArguments);

The CommandBufferType should be specified.

I dont know how unity implement the object to world matrix in DrawMeshInstancedIndirect, but usually the matrix should be passed by cbuffer.

 

Oh yeah, I had that before, must have removed it accidentally before posting. This, as well as the fact that I somehow had the 'INSTANCING_ON' keyword set on my material (only accessible in the debug view!) were the issues. Changing them both got Indirect working!