D3D12_DESCRIPTOR_HEAP_DESC desc = {};
desc.Type = D3D12_DESCRIPTOR_HEAP_TYPE_CBV_SRV_UAV;
desc.NumDescriptors = 1;
desc.Flags = D3D12_DESCRIPTOR_HEAP_FLAG_SHADER_VISIBLE;
pDevice->CreateDescriptorHeap(&desc, IID_PPV_ARGS(&g_pd3dSrvDescHeap));

ImGui_ImplDX12_Init(
    pDevice,
    3, // Buffer count (triple buffering)
    DXGI_FORMAT_R8G8B8A8_UNORM,
    g_pd3dSrvDescHeap,
    g_pd3dSrvDescHeap->GetCPUDescriptorHandleForHeapStart(),
    g_pd3dSrvDescHeap->GetGPUDescriptorHandleForHeapStart()
);