The CHARISMATIC Approach to Modelling and Rendering of Historic Urban Environments

The Charismatic research project (www.charismatic-project.com) is about the production and the interactive rendering of complete reconstructions of populated Cultural Heritage Sites. Both the re-creation and the 3D rendering of virtual reconstructions of city-sized historic environments are technically quite difficult. In order to accomplish them, a full range of approaches and tools were developed in the course of the project. Their underlying idea is to exploit domain knowledge, and also the semantics, of the types of objects to be re-created in order to make the modelling of virtual reconstructions less cost-intensive. As an example, the tool-set includes techniques such as shells, i.e. deformable boxes that can be flexibly distorted, textured, and combined,their arrangement in a specially-tailored hierarchical scene-graph, and alsomulti-resolution data structures such as progressive meshes and subdivision surfaces for free-form ornaments attached to shells. The same structural and semantic information useful for modelling is also exploited by the Charismatic renderer: Interactive display is optimised by applying appropriately chosen level-of-detail and culling techniques. In summary, we present a tool-box of different techniques, designed to make the modelling and rendering of city-sized models feasible, covering as many aspects of this challenging task as possible.