Interactive three-dimensional reconstruction and weathering simulations on buildings

Architectural sites suffers from weathering effects such as liquid sedimentation, lampblack or pollution deposit, moss growing or long-term erosion. Displaying their impact on present buildings could help deciders to plan relevant actions for preserving the architectural heritage. In this paper we present a user-friendly solution for on-line acquiring a semi-physical model from one or few images of a building, immediately followed by real-time simulations. The goal is certainly not to give an accurate prediction of what will happen, but rather to show a plausible state of the site under various possible degradations arising from natural effects. The solution relies on the coupling of two 3-D modelling programs: one dedicated to interactive reconstructions and a second to discreet manipulation for natural phenomena simulations based on a combination of different surface cellular automata. Several experiments were held to estimate the effectiveness of this approach and to identify future works in order to cope with present limitations. A first series applies a lampblack deposit simulation on a large-size 3-D model to demonstrate the solution feasibility and to provide indications about achievable performance. The second series focuses on the solution sensitiveness to both geometrical and semi-physical models granularity through the application of a stone erosion effect on a smaller but less regular-shaped building model. The third series demonstrates the discreet model ability to simulate multiple effects with the example of a vegetation growth simulation. Guidelines for future works are given in the conclusion of this paper.