Procedural Modeling of Buildings
📜 Abstract
CGA shape, a novel shape grammar for the procedural modeling of CG architecture, produces building shells with high visual quality and geometric detail. It produces extensive architectural models for computer games and movies, at low cost. Context sensitive shape rules allow the user to specify interactions between the entities of the hierarchical shape descriptions. Selected examples demonstrate solutions to previously unsolved modeling problems, especially to consistent mass modeling with volumetric shapes of arbitrary orientation. CGA shape is shown to efficiently generate massive urban models with unprecedented level of detail, with the virtual rebuilding of the archaeological site of Pompeii as a case in point.
✨ Summary
The paper introduces CGA shape, a sequential, rule-based grammar for generating detailed building models from volumetric mass models. Its main technical contributions are oriented scopes, split, repeat, and component-split operations; stochastic rule selection; and context-sensitive spatial queries based on occlusion and snapping. These mechanisms allow façade and roof details to remain consistent with complex, rotated, and overlapping building masses. The reported demonstrations include procedural models of individual buildings, office buildings, single-family homes, Pompeii, and large suburban environments.
The work became a foundation for the CGA procedural modeling language used in CityEngine. Current CityEngine documentation continues to describe CGA rules as instructions for automatically generating architectural geometry from building footprints and other initial shapes, while tutorials retain the paper’s mass-modeling concepts such as L- and U-shaped building volumes. (asu.elsevierpure.com) Subsequent research has explicitly treated Müller et al.’s method as a seminal basis for procedural building modeling and has extended CGA-like grammars toward semantically enriched building models, round architectural geometry, and automated ruleset rewriting. (sciencedirect.com)