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# DX11 DX11 Instancing question

## 5 posts in this topic

Hi everyone,

Based on this tutorial: http://www.rastertek.com/dx11tut37.html

can someone point to me some hints on how to pass the rotation of the Instances to the shader?

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Replace the instance position inside VertexInputType by a matrix.

You could also use an array of matrices (inside constant buffer) and index it using SV_InstanceID.

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you mean like that ?

struct VertexInputType
{
float4 position : POSITION;
float2 tex : TEXCOORD0;
matrix instancePosition;
};



and in what way should I modify the D3D11_INPUT_ELEMENT_DESC ?

        polygonLayout[2].SemanticName = "TEXCOORD";
polygonLayout[2].SemanticIndex = 1;
polygonLayout[2].Format = DXGI_FORMAT_R32G32B32_FLOAT;
polygonLayout[2].InputSlot = 1;
polygonLayout[2].AlignedByteOffset = 0;
polygonLayout[2].InputSlotClass = D3D11_INPUT_PER_INSTANCE_DATA;
polygonLayout[2].InstanceDataStepRate = 1;


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You will need multiple elements inside the InputLayout describing the matrix (incrementing the SemanticIndex and AlignedByteOffset).

The DirectX SDK (june 2010) has a sample about instancing that uses this method ( inside the Direct3D10 folder, so minor changes might be needed to adapt it to Dx11)

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• looks like  passing the rotation with TEXCOORD is not possible.
• using an  array of matrices (inside constant buffer) and index it using SV_InstanceID works with rotation, but it can only pass 1024 matrix meaning i can only have 1024 instances of the same model.
• looking at the DirectX SDK(Direct3D10 folder, Instancing10) i find that is doing Instancing with this  "row_major float4x4 mTransform : mTransform;" but i have idea how to use this in dx11, in order to get  Instance with rotation and in large numbers like 10k not just 1024.

any ideals?

Edited by michaelmk86
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