IDXGISwapChain::GetBuffer method (dxgi.h)
Accesses one of the swap-chain's back buffers.
HRESULT GetBuffer( UINT Buffer, REFIID riid, void **ppSurface );
A zero-based buffer index.
If the swap chain's swap effect is DXGI_SWAP_EFFECT_DISCARD, this method can only access the first buffer; for this situation, set the index to zero.
If the swap chain's swap effect is either DXGI_SWAP_EFFECT_SEQUENTIAL or DXGI_SWAP_EFFECT_FLIP_SEQUENTIAL, only the swap chain's zero-index buffer can be read from and written to. The swap chain's buffers with indexes greater than zero can only be read from; so if you call the IDXGIResource::GetUsage method for such buffers, they have the DXGI_USAGE_READ_ONLY flag set.
The type of interface used to manipulate the buffer.
A pointer to a back-buffer interface.
Returns one of the following DXGI_ERROR.