SwapChain

A swap chain is a collection of buffers used to present rendered images to a display, enabling a separation between rendering and presentation. It allows an application to render frames at its own pace while the display updates at a fixed rate, helping reduce tearing and stutter.

A swap chain typically contains a front buffer, which is currently being displayed, and one or more back buffers, which are rendered to. When a frame is ready, the swap operation presents a back buffer by swapping it with the front buffer or by a similar mechanism, depending on the graphics API and mode. Modern graphics pipelines commonly use double or triple buffering to balance latency and throughput.

Configuration of a swap chain usually includes the image format, dimensions, usage flags, and a present mode or swap effect that determines how the swap is performed and whether vertical synchronization is used. Present modes can favor immediate presentation, wait for VSync, or use techniques like mailbox or FIFO to reduce latency or tearing.

Rendering with a swap chain follows a typical cycle: acquire a back buffer from the swap chain, render the frame to that buffer, synchronize to ensure rendering completes, and then present the buffer back to the display. Proper synchronization with semaphores or fences is important to avoid overwriting in-flight buffers. If the window or surface is resized, the swap chain is often recreated with new dimensions.

Different graphics APIs expose the swap chain concept with variations. In DirectX, an IDXGISwapChain manages the buffers and is presented via Present. In Vulkan, a swap chain comprises VkImages and is presented with vkQueuePresentKHR. In OpenGL, glSwapBuffers swaps the front and back buffers of the current context.