The matte control tool combines matte refinement, despill, and edge treatment in one tool. It is a very flexible tool that you can combine with other keying tools or use standalone whenever you have to work on masks.
Great keying results come from high-quality keying workflows that consider all aspects of the problem. Often it helps to separate out certain aspects into individual nodes. Work on the fine edges, fill the wholes, despill, edge refinement, relighting, and more.
The matte control tool offers support in each of those areas. You can use it to apply solid or garbage masks outside your keying tools, do separate despill operations, or even start with some simple mathematical functions to create custom edge masks for relighting.
Watch the tutorial to learn about the most common tasks as well as some creative use cases.