Abstract: Embodiments of the invention provide a method for creating a complete 3D model of complex infrastructure configurations, such as divided highways, roadway intersections, etc. Current CAD applications have been limited to creating 3D models based on the geometry of a single alignment. In one embodiment, each baseline for a 3D model using four data inputs: a topographical terrain model, an alignment specifying the longitudinal 2D geometry for the structure being modeled, a profile specifying the elevations of the baseline along the horizontal alignment, and the geometry for cross-sectional assemblies along the horizontal and vertical alignments.

Abstract: A computer-implemented graphics system for creating and editing interactive constraint-based alignment objects. One or more drawing entities are created in the graphics system, wherein the drawing entities are linked together as an alignment object, and one or more of the entities includes a persistent tangency rule. The drawing entities comprise lines, arcs and/or spirals, although other entities are possible. The drawing entities are then edited in the graphics system, wherein the persistent tangency rules affect the drawing entities' geometry while the drawing entities are being edited. The persistent tangency rule comprises: (1) no tangency, (2) tangency to an entity before or after, or (3) tangency to an entity before and after.