Question RenderMeshIndirect : startInstance doesn't appear to work?

Hi,

Trying to use this for high performance instancing. Was hoping to offset from the buffer to draw on a proportion of instances. Say I have 10000 instances, I want to draw just 1000-1500, so startInstance = 1000, instanceCount = 500.

But startInstance seems to be 0 regardless, or am I reading wrong what it does?

Code (CSharp):

1.         // Indexes per mesh
2.         GB_commandData[0].indexCountPerInstance = mesh.GetIndexCount(0);
3.         // Initial vertex index in mesh
4.         GB_commandData[0].baseVertexIndex = 0;
5.         // Instances to draw
6.         GB_commandData[0].instanceCount = (uint)drawInstances;
7.         // Initial instance/offset to draw?
8.         GB_commandData[0].startInstance = (uint)startInstance;
9.  
10.         GB_commandBuffer.SetData(GB_commandData);
11.  
12.         Graphics.RenderMeshIndirect(in renderParams, mesh, GB_commandBuffer);

 

Thought maybe it's due to using ShaderGraph, but on using a basic instancing shader still doesn't appear to start at startInstance.

 

Ok figured it out only for non-ShaderGraph, on Vulkan it's GetIndirectInstanceID, but DX is GetIndirectInstanceID_Base (in shader code if using "UnityIndirect.cginc"). So how to access in ShaderGraph without a custom property?