Procedural generation and weathering of building facades : Replicating shape and distribution of wear-and-tear on real-world building facades

Abstract: Manual modeling of building facades can be a cumbersome process. Instead, procedurally modeling building facades is a practical and quick way to achieve impressive visual results. This paper presents a method for prototyping 2D facades existing in a 3d environment, with the inclusion of shading-based procedural wear-and-tear. State of the art procedural modeling techniques, despite achieving impressive results in general, are lacking in certain specific areas. Urban planners may wish to model the effects of wear-and-tear along with geometric assets and materials on a facade, to prototype future appearances. As of now, a syncretism between a grammar-based procedural modeling system and a procedural wear-and-tear system is relatively unexplored. Exploring how wear-and-tear can replicate damage found on real buildings, and limitations of the used approach, is the primary goal of this research. Furthermore, this work investigates how wear-and-tear can be incorporated into a procedural building facade generation pipeline. Introducing new wear-and-tear functionality to established systems is done by expanding on grammar-like structures to define building shapes, and adding new actions to produce wear-and-tear, which is done by creating textures representing positions of structural components of the facade, and altered and mixed with noise to create damaging effects. The result is a user interface that can combine procedural building modeling with procedural wear-andtear. It can replicate many types of wear-and-tear, such as rust and cracks, although damage such as stains without visible sources or flow-shaped damage is inadequate. The facades accompanying the wear-and-tear are also able to be produced, but is limited in terms of 3D geometric expressibility due to a focus on flat, 2D facades and a deficiency in future flexibility since wear-and-tear cannot be selected in future actions.