Computer Description of Bodies Bounded by Quadric Surfaces from a Set of Imperfect Projections

This paper describes a computer program for constructing a description of solid bodies from a set of pictures taken from different vantage points. The bodies are assumed to be bounded by faces which are planar or quadric, and to have vertices formed by exactly three faces It is assumed that a preprocessor provides the program with line and junction information which it has extracted from the pictures. The preprocessor is expected to make mistakes, such as losing features or providing misinformation about their nature. A technique is presented for validating doubtful features as well as for matching corresponding features extracted from the different pictures. New grammar rules are developed for linedrawing projections of curved and planar bodies and are used as a tool in the scene analysis process. Each picture's data analysis is supported dynamically by the results obtained thus far in the other pictures' analysis. The analyzed data from all pictures are grouped into sets, each corresponding to a single face (flat or curved), whose nature is also determined. The sets are grouped again to correspond to the different bodies in the scene. The program written in PL/I has been tested successfully on several scenes.