Rendering APIs typically provide just enough functionality to abstract a graphics accelerator, focussing on rendering primitives, state management, command lists/command buffers; and as such differ from fully fledged 3D graphics libraries, 3D engines (which handle scene graphs, lights, animation, materials etc.), and GUI frameworks; Some provide fallback software rasterisers, which were important for compatibility and adoption before graphics accelerators became widespread. Some have been extended to include support for compute shaders.