An architectural approach to efficient 3D urban modeling

A 3D reconstruction of an urban area for Virtual Worlds (VWs) or Serious Games (SGs) requires a careful trade-off among the 3D models' realism, weight and development time. This has led us to the definition of an algorithm – the Architectonic Style Area (ASA) algorithm – for procedural generation of buildings in an urban area, based on the concept of “architectonic likelihood”, that intends to give players the sense of being in a particular city or even specific area of a city. This has a cognitive foundation in the fact that, after a visit, a tourist typically does not remember every single palace of a city, but remembers – beside the most important monuments and buildings – its general features and its architectonic styles. The algorithm extrudes 2D maps and composes façades by statistically assembling sample images of architectonic components from the target city. Components are classified in an ontology based on the classic principles of architecture. The algorithm relies on rules that encode the semantics of the ontology.The paper describes the algorithm and the related easy-to-use visual authoring tool. It also shows the results in two different projects: a SG for the promotion of the cultural heritage and a 3D movie. Results show that the approach allows keeping the realism of every single building at good detail and of the overall scene, while dropping a huge work of image collection and processing for the textures.Comparisons are investigated with regard to state of the art urban modeling methods, highlighting the differences and possible synergies.

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► Trade-off among the 3D models' realism, weight and development time for real-time applications.
► The “architectonic likelihood” principle: to give users the sense of being in a particular city or specific area of a city.
► Composition of facades by statistically assembling 2D/3D samples of architectonic components from the target city area.
► Algorithm based on rules that encode the semantics of an ad-hoc architectural ontology.
► Discussion on comparison and synergies with state of the art of procedural modeling.