Digital compositing workflows are of two types :
Node-based compositing – The entire composite is a tree like graph, laying out everything from the source media objects to the final output in the form of a map of nodes. It allows great flexibility for going in and modifying the process steps. But these are not effective in handling keyframing and time effects because the workflow does not stem from a time line.
Eg: Apple Shake, Blender, EyeOn fusion, Foundry Nuke
Layer-based compositing – Each media object is a separate layer in the timeline, each with its own time bounds, effects and keyframes. Well suited for quick 2D motion graphics; becomes awkward for complex composites with many layers. The composite order of elements can be viewed in a flowchart.
Eg: After Effect