Maybe you are thinking of the amplituhedron [1] which can make calculations of interaction amplitudes much easier than summing up a large number Feynman diagram

Maybe you are thinking of the amplituhedron [1] which can make calculations of interaction amplitudes much easier than summing up a large number Feynman diagram. [1] https://en.wikipedia.org/wiki/Amplituhedron https://en.wikipedia.org/wiki/Amplituhedron