Advances in modeling of discrete models have allowed the development of approaches for direct mesh modeling and modification. These tools mainly focus on modeling the visual appearance of the shape which is a key criterion for animation or surgical simulation. Most of the time, the resulting mesh quality as well as the semantics preservation capabilities are not considered as key features. These are the limits we overcome in this paper to enable fast and efficient mesh modifications when carrying out numerical simulations of product behaviors using the Finite Element (FE) analysis. In our approach, the modifications involve the resolution of an optimization problem where the constraints come from the shapes of the operating tools and the FE groups (sets of mesh entities) used to support the semantic information (e.g. boundary conditions, materials) contained in the FE mesh model and required for FE simulation. The overall mesh quality, a key point for accurate FE analysis, is guaranteed while minimizing an objective function based on a mechanical model of bar networks which smoothes the repositioning of nodes. Principle of the devised mesh operators is exemplified through the description of a 2D/3D mesh drilling operator. The proposed mesh modification operators are useful in the context of fast maintenance studies and help engineers to assess alternative design solutions aimed at improving the physical behavior of industrial machinery.

The study of historic buildings is usually based on the collection and analysis of iconographic sources such as photographs, drawings, engravings, paintings or sketches. This paper describes a methodological approach to make use of the existing iconographic corpus for the analysis and the 3D management of building transformations. Iconography is used for different goals. Firstly, it's a source of geometric information (image-based-modeling of anterior states); secondly, it's used for the re-creation of visual appearance (image-based texture extraction); thirdly it's a proof of the temporal distribution of shape transformations(spatio-temporal modeling); finally it becomes a visual support for the study of building transformations (visual comparison between different temporal states). The aim is to establish a relation between the iconography used for the hypothetical reconstruction and the 3D representation that depends on it. This approach relates to the idea of using 3D representations like visualization systems capable of reflecting the amount of knowledge developed by the study of a historic building.

Visualisation, assembling/disassembling simulation, reverse engineering, or finite element analyses are so many applications where a polyhedral simplification can be mandatory. In most of the configurations, such an operation must preserve the significant shapes of the original model. This paper addresses the way these simplifications can be performed while preserving character lines, i.e. those lines which affect significantly the object visual appearance. The proposed simplification process is based on a vertex removal algorithm that uses a heterogeneous map of sizes computed with information extracted from 2D images of the object. The farther the vertices are from the character lines, the more the simplification is important. The geodesic distances are estimated while using a new algorithm based on the analysis of multiple filtering of the images. This method might reduce the computational time since there is no need to compute either the curvature or the saliency. Thus, a first attempt to enrich a polyhedral model with semantic information extracted from images is proposed.