The use of gradient and dual space in line-drawing interpretation

摘要: This paper reviews the application of gradient space and dual in programs that interpret line-drawings examines whether they can provide a basis for fully adequate program. Mackworth's program Poly is analyzed at length. Counterexamples show first procedure must be generalized from to space, then constraints form inequalities as well equations handled which necessitates radical re-design. A proof itself valid under perspective orthographic projection although its derivation terms not, further indicates (or dual) not important element approach. Other ways using by Kanade Huffman are discussed but do convincingly rebut conclusion peripheral design competent Finally plane equation approach derived developments described, while theoretically adequate, awkward use because it fails offer intuitive clarity, supported contrasting with alternative method sidedness reasoning.