Nancy Hitschfeld-Kahler

Designing a product family of meshing tools

Applying software engineering concepts can improve the quality of any software development, and this is even more dramatic for complex, large and sophisticated software, such as meshing tools. Software product families are series of related products that make intensive reuse of already developed components. Object-oriented design promotes reusability, so it is specially suited for designing the structure of product families. In this paper we present an object-oriented design of a product family of meshing tools, where all family members share the software structure. By instantiating the structure with particular algorithms and parameters, we can easily produce different tools of the family. A good family design allows us not only to combine existing algorithms but also to easily incorporate new ones, improving software family evolution. We show how the family design is used for the generation of finite element and finite volume meshing tools, as well as a new tool for image processing.

A TOOL BASED ON DL FOR UML MODEL CONSISTENCY CHECKING

Automated consistency checking of UML models becomes necessary as models grow in size and complexity. Since the UML metamodel does not enforce model consistency, there are no fixed guidelines on how to approach the consistency problem. Current solutions are generally partial. The translation of the metamodel and the user designed model into Description Logics has proved to provide a solution in detecting a large set of inconsistencies. In order to make this solution available to system designers, we have implemented MCC+, a UML model consistency checker, built as a plug-in for Poseidon for UML, and relying on Jena as a reasoning engine. Compared to other approaches, we propose a usable and scalable solution, interoperable with a known modeling tool. We show the application of MCC+ to a real world large example of a meshing tool.

Robust tree-ring detection

The study of tree-rings is a common task in dendrology. Usually the rings deliver information about the age of the tree, historic climate conditions and forest densities. Many different techniques exist to perform the tree-ring detection, but they commonly are semi-automatic. The main idea of this work is to propose an automatic process for the tree-ring detection and compare it with a manual detection made by an expert in dendrology. The proposed technique is based on a variant of the Generalized Hough Transform (GHT) created using a very simple growing model of the tree. The presented automatic algorithm shows tolerance to textured and very noisy images, giving a good tree-ring recognition in most of the cases. In particular, it correctly detects the 80% of the tree-rings in our sample database.

Generation of 3D mixed element meshes using a flexible refinement approach

This paper describes and discusses the main characteristics and implementation issues of a 3D mixed element mesh generator based on a generalization of the modified octree approach. This mesh generator uses primitive elements of different type as internal nodes, a flexible refinement approach as refinement strategy (primitive elements are not always bisected), and bricks, pyramids, prisms and tetrahedra as final elements. The mesh generation process is divided in several steps: the generation of the initial mesh composed of primitive elements, the refinement of primitive elements until the point density requirements are fulfilled, the generation of a graded mesh between dense and coarse regions, and finally, the recognition of the final elements. The main algorithms and data structures are described in detail for each step of the mesh generation process. As result, examples of meshes that satisfy the Delaunay condition and that can be used with the control volume method are shown.

Product line architecture for a family of meshing tools

Meshing tools are traditionally built in a one by one basis without reusing already developed parts. However, there are several concepts within this application domain that are present in most tools. Developing software components implementing these concepts is extremely time consuming and requires highly specialized programmers. Software product lines is a way of systematically reusing assets. We propose a layered product line architecture for meshing tools. We specify it formally using xADL, and we show that it fits some already built tools.

Animation of generic 3D head models driven by speech

In this paper, a system for speech-driven animation of generic 3D head models is presented. The system is based on the inversion of a joint Audio-Visual Hidden Markov Model to estimate the visual information from speech data. Estimated visual speech features are used to animate a simple face model. The animation of a more complex head model is then obtained by automatically mapping the deformation of the simple model to it. The proposed algorithm allows the animation of 3D head models of arbitrary complexity through a simple setup procedure. The resulting animation is evaluated in terms of intelligibility of visual speech through subjective tests, showing a promising performance.

Clustering of 3D Spatial Points Using Maximum Likelihood Estimator over Voronoi Tessellations: Study of the Galaxy Distribution in Redshift Space

This paper describes an algorithm based on the 2D approach of Allard & Fraley that uses Voronoi tessellation and a non-parametric maximum likelihood estimator. We have designed a 3D version of this algorithm which detects multiple clusters of points immersed in background noise; its application to the detection of galaxy clusters in red-shift space, using the astronomical database of the 2-degree Field Galaxy Redshift Survey, is presented and discussed. Adopting as a benchmark a particular set of catalogued clusters of galaxies, we find that the proposed algorithm recognizes the location of ~67% of the clusters. Three variants of the algorithm were assessed to deal with the elongation of the clusters in the radial direction of observation introduced by the astronomical distance indicator; their merits and limitations are discussed. We address separately the detection of the galaxy cluster location and the detection of galaxy cluster members, both of them having an anisotropic space as their search domain. In the case of detection of galaxy cluster members, a second stage of detection was incorporated in order to improve the results.

On Finding Large Polygonal Voids Using Delaunay Triangulation: The Case of Planar Point Sets

In astronomy, the objective determination of large empty spaces or voids in the spatial distribution of galaxies is part of the characterization of the large scale structure of the universe. This paper proposes a new method to find voids that starting from local longest-edges in a Delaunay triangulation builds the largest possible empty or almost empty polygons around them. A polygon is considered a void if its area is larger than a threshold value. The algorithm is validated in 2D points with artificially generated circular and non-convex polygon voids. Since the algorithm naturally extends to 3D, preliminary results in 3D are also shown.

Domain modeling as a basis for building a meshing tool software product line

Meshing tools are highly complex software for generating and managing geometrical discretizations. Due to their complexity, they have generally been developed by end users - physicists, forest engineers, mechanical engineers - with ad hoc methodologies and not by applying well established software engineering practices. Different meshing tools have been developed over the years, making them a good application domain for Software Product Lines (SPLs). This paper proposes building a domain model that captures the different domain characteristics such as features, goals, scenarios and a lexicon, and the relationships among them. The model is partly specified using a formal language. The domain model captures product commonalities and variabilities as well as the particular characteristics of different SPL products. The paper presents a rigorous process for building the domain model, where specific roles, activities and artifacts are identified. This process also clearly establishes consistency and completeness conditions. The usefulness of the model and the process are validated by using them to generate a software product line of Tree Stem Deformation (TSD) meshing tools. We also present Meshing Tool Generator, a software that follows the SPL approach for generating meshing tools belonging to the TSD SPL. We show how an end user can easily generate three different TSD meshing tools using Meshing Tool Generator.

Generic Face Animation

In computer vision, the animation of objects has attracted a lot of attention, specially the animations of 3D face models. The animation of face models requires in general to manually adapt each generic movement (open/close mouth) to each specific head geometry. In this work we propose a technique for the animation of any face model avoiding most of the manual intervention. In order to achieve this we assume that: (1) faces, despite obvious differences are quite similar and a single generic model can be used to simplify deformations and (2) using this face model, a simple interpolation technique can be used, with minimal manual intervention. Several examples are presented to verify the realism of the obtained animations.