Section: Bilateral Contracts and Grants with Industry

Bilateral Contracts with Industry

Geometry

We contributed to some industrial applications, mainly:

• Aircraft industry: Design of winglets (with EADS)

  In this project, our aim was to improve the geometric preprocessing of the CAD models generation that were used for the manufacturing of the multi parted wing-fuselage configuration and the generation of the numerical grids for the corresponding numerical simulations. We try developing algorithms for automatic generation of winglets with different bending radii, angles and top views. Some of the methods for approximation, fairing, modeling and grid generation used for this task are in principle well known in literature. However, standard commercial CAD systems cannot be used for the modeling of the surfaces because they do not provide the interfaces to fulfill the special constraints, which stem from the design wishes and the manufacturing and the needs of the applied flow solver for the aerodynamics equations.

• NC Simulation (with Spring Technologies)

  The aim of this work was to rebuild a CAD file (Brep, STEP format) from the result of a machining simulation (set of triangles). Any CAM software would use this reverse engineered model for any further application (inspection / FEM / definition of further tool paths). Another expected application was to rebuild CAD files from old G -code programs for which the initial CAD files do not exist anymore (or had never been modeled in 3D). Spring NCSimul provides a set of triangles as a solid. This set is topologically closed and represents a single solid. All data could be used to help gather triangles by geometric entities and then to help compute the exact surfaces. Different types of machining operations have been considered: Machining of simple shapes: The movement of the tool generates the same kind of surfaces as the tool ones: planes, cylinders, torus, etc. and Machining of complex shapes: the tool moves on a surface (canonic surface as well as NURBS surface) along a point-to-point path. Here, the reverse engineering is far from straightforward and the surface recognition would be computed at a tolerance.

• Dam Construction (with CHIDI / Dassault System)

  Once the digital terrain modeling and the geological shapes are represented, dam design issue is one of the most important difficult applications for geological modeling. This issue considers a multiple geometric representation of geological and design features. The dam design is based on NURBS surfaces representation and parametric design is an important key point when modifying shape or geometrical parameters and properties. In the other hand, geological shapes are mesh-based (surface meshes for geometrical characteristics, and volume meshes for material and engineering properties). In the plant interaction, we have impact the dam basement on the geological modeling. That is to say, remove a solid to a mesh. Then map geological properties to the solid. At this time, there was no feasible well-designed NURBS-Mesh Boolean operation algorithm in both research and industrial field and the aim of our work was to develop a stable NURBS-Mesh Boolean operation algorithm. This long-term work was developed for the CHIDI Company (Chengdu) with the participation of Dassault System. Moreover, in order to provide simulations after the Earthquake in Sichuan, we first focused our work on the Boolean operation algorithms.

Computer Graphics

Image resizing (with Shanghai Film Studio)

We have developed an image resizing method that succeed in generating impressive results by using image similarity measure to guide the resizing process. An optimal operation path is found in the resizing space.

However, the slow resizing speed caused by inefficient computation strategy of the bidirectional patch matching becomes a drawback for practical use. Then, we proposed a novel method to address this problem. By combining seam carving with scaling and cropping, our method can realize content-aware image resizing very fast. We define cost functions combing image energy and dominant color descriptor for all the operators to evaluate the damage to both local image content and global visual effect. Therefore our algorithm can automatically find an optimal sequence of operations to resize the image by dynamic programming or greedy algorithm. We also extended our algorithm to indirect image resizing which can protect the aspect ratio of the dominant object in an image.