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I am trying to implement hardware instancing with Direct3D 10+ using Structured Buffers for the per instance data but I've not used them before.

I understand how to implement instancing when combining the per vertex and per instance data into a single structure in the Vertex Shader - i.e. you bind two vertex buffers to the input assembler and call the DrawIndexedInstanced function.

Can anyone tell me the procedure for binding the input assembler and making the draw call etc. when using Structured Buffers with hardware instancing? I can't seem to find a good example of it anywhere.

It's my understanding that Structured Buffers are bound as ShaderResourceViews, is this correct?

gareththegeek
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Yup, that's exactly right. Just don't put any per-instance vertex attributes in your vertex buffer or your input layout and create a ShaderResourceView of the buffer and set it on the vertex shader. You can then use the SV_InstanceID semantic to query which instance you're on and just fetch the relevant struct from your buffer.

StructuredBuffers are very similar to normal buffers. The only differences are that you specify the D3D11_RESOURCE_MISC_BUFFER_STRUCTURED flag on creation, fill in StructureByteStride and when you create a ShaderResourceView the Format is DXGI_UNKNOWN (the format is specified implicitly by the struct in your shader).

StructuredBuffer<MyStruct> myInstanceData : register(t0);

is the syntax in HLSL for a StructuredBuffer and you just access it using the [] operator like you would an array.

Is there anything else that's unclear?

Adam Miles
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  • Thanks very much, that helps a lot. On the DrawIndexedInstanced MSDN article it states "Instancing requires multiple vertex buffers: at least one for per-vertex data and a second buffer for per-instance data" which confused me a bit. So I can call DrawIndexedInstanced with only one Vertex Buffer bound to the Input Assembler and just make sure my input mapping only uses the one vertex buffer? – gareththegeek Jul 31 '13 at 07:43
  • That's my understanding, yes. You don't need per-instance vertex attributes to use instancing if you don't want to. – Adam Miles Jul 31 '13 at 12:53