Node graph architecture is a software design structured around the notion of a . Both the source code as well as the user interface is designed around the editing and composition (or linking) of atomic functional units. The user interface of the software application will often visually display the node graph to the user. This is often accomplished by using the GPU to perform the rendering which is subsequently displayed on the desktop to the user. Common APIs for the GPU are OpenGL and DirectX. Nodes are often drawn as rectangles, and connections between nodes are drawn with lines or splines.