DirectX11-硬件多实例渲染

1.设置输入装配描述符
关键字：D3D11_INPUT_PER_INSTANCE_DATA
注意矩阵的更新方式，因为DXGI_FORMAT一次最多仅能够表达128位(16字节)数据，在对应矩阵的语义时，需要重复描述4次，区别在于语义索引为0-3.

const D3D11_INPUT_ELEMENT_DESC GameApp::VertexPosColor::inputLayout[] = {
    { "POSITION", 0, DXGI_FORMAT_R32G32B32_FLOAT, 0, 0, D3D11_INPUT_PER_VERTEX_DATA, 0 },
    { "COLOR", 0, DXGI_FORMAT_R32G32B32A32_FLOAT, 0, 12, D3D11_INPUT_PER_VERTEX_DATA, 0 },
    { "World", 0, DXGI_FORMAT_R32G32B32A32_FLOAT, 1, 0, D3D11_INPUT_PER_INSTANCE_DATA, 1},
    { "World", 1, DXGI_FORMAT_R32G32B32A32_FLOAT, 1, 16, D3D11_INPUT_PER_INSTANCE_DATA, 1},
    { "World", 2, DXGI_FORMAT_R32G32B32A32_FLOAT, 1, 32, D3D11_INPUT_PER_INSTANCE_DATA, 1},
    { "World", 3, DXGI_FORMAT_R32G32B32A32_FLOAT, 1, 48, D3D11_INPUT_PER_INSTANCE_DATA, 1}
};

2.创建实例缓冲区
注意：需要能够动态更新

 D3D11_BUFFER_DESC vbd;
    ZeroMemory(&vbd, sizeof(vbd));
    vbd.Usage = D3D11_USAGE_DYNAMIC;
    vbd.ByteWidth = sizeof(InstancedData) * instances.size();
    vbd.BindFlags = D3D11_BIND_VERTEX_BUFFER;
    vbd.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
    D3D11_SUBRESOURCE_DATA InitData;
    ZeroMemory(&InitData, sizeof(InitData));
    InitData.pSysMem = instances.data();
    HR(m_pd3dDevice->CreateBuffer(&vbd, &InitData, m_pInstanceBuffer.GetAddressOf()));

3.输入装配阶段设置顶点缓冲和实例缓冲

   // 输入装配阶段的顶点缓冲区设置
    UINT strides[2] = { sizeof(VertexPosColor), sizeof(InstancedData)};	// 跨越字节数
    UINT offsets[2] = { 0,0};
    ID3D11Buffer* buffers[2] = { m_pVertexBuffer.Get(), m_pInstanceBuffer.Get() };// 起始偏移量

    m_pd3dImmediateContext->IASetVertexBuffers(0, 2, buffers, strides, offsets);

4.绘制实例

 m_pd3dImmediateContext->DrawIndexedInstanced(6, m_instancedNum, 0, 0, 0);

5.着色器设置
实例缓冲区的数据全都设置到顶点输入结构体中

struct VertexIn
{
    float3 posL : POSITION;// 来自输入槽0
    float4 color : COLOR;// 来自输入槽0
    matrix world : World;		// 来自输入槽1
};