Olivier Terraz

3Gmap L-systems: an application to the modelling of wood

In this paper an extension of L-systems is proposed, based on three-dimensional (3D) generalized maps that allow an easier control of the internal structure of 3D objects. A first and original application of this extension is also proposed: wood modelling by growth simulation. Numerous other applications of our work are possible, in the area of computer graphics, as well as in botanical science.

Modeling and Rendering of Heterogeneous Granular Materials: Granite Application

Light‐matter interactions is one of the most important factors of realistic rendering. While a lot of work has already been performed in the light transport and simulation area, we believe that “virtual materials” have not yet been studied enough to achieve a high degree of realism. Some good models exist in order to take into account homogeneous materials. However, there are only a few studies of heterogeneous granular materials. In this paper, we propose a method based on mimicking natural phenomena to take into account these materials. Our study focuses on granite, which can be considered as a heterogeneous agglomerate of individually homogeneous grains. First we present a nucleation/growth process inspired technique giving a full 3D model of granite. Then, we use a rendering process taking into account each material component and subsurface scattering in a simple way.

Generalized maps for erosion and sedimentation simulation

Abstract We propose a new approach, based on dynamic animation, to simulate geomorphological events such as erosion, sediment transportation and deposition. It relies on a generalized map representation of different geological layers. The topological evolution of these layers is driven by a set of displacements applied onto the vertices. The topological consistency of the model is guaranteed by a collision detection system that handles vertices, edges, or faces through generic operations. Experimental results show the ability of this approach to simulate various evolution scenarios studied in geology. Fluid simulation is added to implement fluid–solid interactions based on a hydrology model. These interactions generate animations of hydraulic erosion and sedimentation phenomena.

Using Visual Representation for Decision Support in Institutional Research Evaluation

Higher Education Institutes worldwide are facing an increased demand to strengthen their capacities for research and innovation. This study introduces an ontology-based software system architecture that supports research policy evaluation processes and decision-making strategies, using visual analytics. A knowledge modeling technique drawing on multi criteria analysis and data visualisation is proposed. In addition, the paper presents a prototype built on Protege, Pellet reasoner and Java Technologies, which is friendly to the user and capable of interactive synthesis of institutional decision support criteria. In this work we make a transition from knowledge to visual web-based decision support systems with different kinds of visualisations. The developed system enables research managers to evaluate key aspects of academic research activity in the context of specific policies and criteria, correlate strategic goals with research performance and make informed decisions on the establishment of research strategies.

Modeling fruits and their internal structure using parametric 3Gmap L-systems

Modeling a fruit using classic 3D modeling software can be a relatively complicated task. Moreover, modeling every single fruit when we need to generate a large variety of fruits of the same species is not a viable option because it is time consuming. This paper presents an original ad hoc method for modeling a wide range of 3D fruits, using a single formal grammar. Fruits are modeled by parametric 3Gmap L-systems that describe their shape and internal structure, thanks to variables and mathematical functions. At the end of our work, our method will eventually be an interesting solution to realistic modeling of fruits and their interior, and to automatic detection and recognition of real fruits.

3Gmap L-Systems Grammar Application to the Modeling of Flowering Plants

Flowering plants have an enormous variety of shapes both within and between individuals, providing a vast area of objectives which the image synthesis must challenge. The structure of a flower has such properties as self-similarity, symmetry, branching arrangement, which make a modeling process quite tedious. We propose to apply mathematical methods to determine botanical natural laws, using 3Gmap L-systems. Describing the structure of a flowering plant with a grammar we are able to obtain an unlimited number of its geometrical interpretations. Our approach combines L-systems grammar writing with interactive control of parameter settings. The L-systems grammars are used for describing the entire model, with stems,stamens, petals, leaves, etc., by simply operating with 3Gmap volumes. The presented contributions will make the task of a user more obvious and intuitive enabling her/him to create more accurate models. 3Gmap L-systems grammars have a nested structure, enabling to use a huge amount of grammars in a more obvious way. Moreover the way the model is built allows us to take into account its internal structure. As the flower tissue is non-homogeneous, the possibility of obtaining its internal composition could be quite useful for rendering, allowing for instance to render more accurate subsurface scattering.

A Hierarchical Hashing Scheme for Nearest Neighbor Search and Broad-Phase Collision Detection

Increasing computational power allows computer graphics researchers to model spectacular phenomena such as fluids and their interactions with deformable objects and structures. Particle-based (or Lagrangian) fluid and solid simulations are commonly managed separately and mixed together for the collision detection phase. We present a unified dynamic acceleration model to be used for particle neighborhood queries and broad-phase collision detection, based on a hierarchical hash table data structure. Our method is able to significantly reduce computations in large, empty areas, and thus gives better results than existing acceleration techniques, such as multilevel hashing schemes or KD-trees, in most situations.

Assessing the performance of educational institutions: A multidimensional approach

Academic units comprise multiple domains that influence their overall performance and synthesize their profile. In order to assist decision makers and examine the impact of the activities and the interactions of Higher Educational Institutions on the domains of which academia is consisted, multivariate rankings are utilized. Rankings can be used as a measure of the development of an academic unit in time and in relation to other academic units, as well as a guide for the strategic planning. Although, multifaceted information gives a clearer interpretation of the status of academic units and contributes to their development, it perplexes the decision making process by increasing its complexity. The paper describes a ranking methodology that considers the multidimensionality of academia, so as to offer a detailed comparison and assessment of educational institutions, but also alleviates the intricacy of multifaceted data by introducing semantic web technologies and visual analytics to the multiple criteria decision making process. The applicability of the methodology to the academic domain is ensured by the competency check, which is a set of requirements that should be satisfied by the domain. In this context, we present the Multidimensional Ontology Based Visual Ranking system, which builds upon the before mentioned methodology and proposes the use of ontologies for storing, managing and exploring the information and visual analytics for providing interactive presentation and insights on complex and voluminous data.

Flower modelling using natural interface and 3Gmap L-systems

In this paper we propose to create virtual glades of flowers using kinect gestures. The user gestures are read and reinterpreted by the kinect interface. Once the gesture is made, and a correspondence to the parameter space of the flower model is done, it is transmitted to a web server which contains a 3Gmap L-system application. 3Gmap L-systems (an extension of L-Systems) are based on three-dimensional generalized maps, and have been successfully applied to the modeling of flowering plants. The 3Gmap L-system receives the command to create or modify the flower and returns the 3D model which will be read and visualised by the Unity game engine.

Modeling of Flowers with Inverse Grammar Generation Interface

Flowers belong to one of the natural phenomena that cannot be captured completely, as there is enormous variety of shapes both within and between individuals. The authors propose a procedural modeling of flowering plants using an extension of L-Systems-a model based on three-dimensional generalized maps. Conventionally, in order to build a model the user has to write the grammar, which consists of the description of 3Gmaps and all the production rules. The process of writing a grammar is usually quite laborious and tedious. In order to avoid this the authors propose new interface functionality: the inverse modeling by automatic generation of L-systems. The user describes the flower he wants to model, by assigning the properties of its organs. The algorithm uses this information as an input, which is then analyzed and coded as L-systems grammar.