Fast visibility analysis in 3D procedural modeling environments

This paper presents a unique solution to the visibility problem in 3D urban environments generated by procedural modeling. We shall introduce a visibility algorithm for a 3D urban environment, consisting of mass modeling shapes. Mass modeling consists of basic shape vocabulary with a box as the basic structure. Using boxes as simple mass model shapes, one can generate basic building blocks such as L, H, U and T shapes, creating a complex urban environment model computing visible parts. Visibility analysis is based on an analytic solution for basic building structures as a single box. A building structure is presented as a continuous parameterization approximating of the building's corners. The algorithm quickly generates the visible surfaces' boundary of a single building and, consequently, its visible pyramid volume. Using simple geometric operations of projections and intersections between these visible pyramid volumes, hidden surfaces between buildings are rapidly computed. Real urban environment from Boston, MA, approximated to the 3D basic shape vocabulary model demonstrates our approach.