Interpreting Line Drawings as Three-Dimensional Surfaces

We propose a computationai modei for interpreting iine drawings as three-dimensionai surfaces, based on constraints on iocai surface orientation aiong extremai and discontinuity boundaries. Specific techniques are described for two key processes: recovering the threedimensionai conformation of a space curve (e.g., a surface boundary) from its two-dimensionai projection in an image, and interpoiating smooth surfaces from orientation constraints aiong extremai boundaries.