Article: Real-time Bounding Box Area Computation
An article on an algorithm for computing the “coverage area” of a box given a perspective camera. See https://www.cg.tuwien.ac.at/research/publications/1999/Fuhr-1999-Conc/TR-186-2-99-05Paper.pdf. The algorithm does not account for viewport clipping however.
A common alternative to this algorithm is “3D to 2D bounding box”