Dimitri Plemenos

Viewpoint quality: measures and applications

Several methods that use the notion of viewpoint quality have been recently introduced in different areas of computer graphics, such as scene understanding, exploration of virtual worlds, radiosity and global illumination, image-based rendering and modelling. In this paper, we analyze the behavior of three different viewpoint quality measures. The first one is a heuristic measure, the second one is the viewpoint entropy, and the third one is a new measure based on the Kullback-Leibler distance between the projected and actual distributions of the areas of the polygons in the scene. In addition, this paper reviews different applications and introduces a new algorithm using the Kullback-Leibler distance for the selection of a representative set of n views. Our method is based in selecting the view that minimizes the Kullback-Leibler distance between the mixture of the distributions of all selected views and the actual area distribution.

Methods and data structures for virtual world exploration

This paper is dedicated to virtual world exploration techniques that help humans to understand a 3D scene. The paper presents a technique to calculate the quality of a viewpoint for a scene, and describes how this information can be used. A two-step method for an automatic real-time scene exploration is introduced. In the first step, a minimal set of “good” points of view is determined; in the second step, these viewpoints are used to compute a camera path around the scene. The proposed method enables one to get a good comprehension of a single virtual artifact or of the scene structure.

Virtual world explorations by using topological and semantic knowledge

This paper is dedicated to virtual world exploration techniques. Automatic camera control is important in many fields as computational geometry, visual servoing, robot motion, graph drawing, etc. The paper introduces a high-level camera controlling approach in virtual environments. The proposed method is related to real-time 3D scene exploration and is made of two steps. In the first step, a set of good viewpoints is chosen to give the user a maximum knowledge of the scene. The second step uses the viewpoints to compute a camera path between them. Finally, we define a notion of semantic distance between objects of the scene to improve the approach.

MultiCAD-GA: A System for the Design of 3D Forms Based on Genetic Algorithms and Human Evaluation

The solution engine of MultiCAD-GA, presented in this work, is a part of a new software environment for efficient search for solutions in heavily demanding applications involving the design of three-dimensional forms, such as those of architectural and interior decoration design. MultiCAD-GA starts by using constraint programming techniques in order to find a set (population) of solutions (forms) that satisfy the spatial constraints imposed by the user and create an initial generation. In the sequel, it applies genetic operators to generate new solutions and interacts with the user in order to evaluate the solutions and increase the speed of convergence to those forms that satisfy his/her aesthetics. The forms are coded into chromosomes using the usual binary strings. Visualization of the results is performed through the VRML graphics language.

Inverse Direct Lighting with a Monte Carlo Method and Declarative Modelling

In inverse lighting problems, a lot of optimization techniques have been used. A new method in the framework of radiosity is presented here, using a simple Monte-Carlo method to find the positions of the lights in a direct lighting. Declarative modelling will also be used to allow the designer to describe in a more intuitive way his lighting wishes. Declarative modelling will propose to the user several solutions, and probably some interesting scenes not previously imagined by the designer.

Intelligent Computer Graphics 2011

Realistic Skin Rendering on GPU.- Affective States in Behavior Networks.- Information Theory Tools for Viewpoint Selection, Mesh Saliency and Geometry Simplification.- Classifying Volume Datasets Based on Intensities and Geometric Features.- Light Source Storage and Interpolation for Global Illumination: A Neural Solution.- An Intelligent System for Overlaying Texts on Background Images Based on Computational Aesthetics.- Parallel Coordinates: Intelligent Multidimensional Visualization.- An Adjectival Interface for Procedural Content Generation.- An SVM/GA Hybrid Framework for Qualitative Knowledge Aided 3D Scene Synthesis.- Machine Learning and Pattern Analysis Methods for Profiling in a Declarative Collaorative Framework.- AURAL: An Evolutionary Interface for a Robotic Sonification Process.

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.

Artificial Intelligence Techniques for Computer Graphics

The purpose of this volume is to present current work of the Intelligent Computer Graphics community, a community growing up year after year. Indeed, if at the beginning of Computer Graphics the use of Artificial Intelligence techniques was quite unknown, more and more researchers all over the world are nowadays interested in intelligent techniques allowing substantial improvements of traditional Computer Graphics methods. The other main contribution of intelligent techniques in Computer Graphics is to allow invention of completely new methods, often based on automation of a lot of tasks assumed in the past by the user in an imprecise and (human) time consuming manner. This volume contains both invited and selected extended papers from the last 3IA Conference (3IA2008), together with an introduction presenting the area of Intelligent Computer Graphics and various Computer Graphics areas where introduction of intelligent techniques permitted to resolve important problems. We hope that this volume will be interesting for the reader and that it will convince him (her) to use, or to invent, intelligent techniques in Computer Graphics and, maybe, to join the Intelligent Computer Graphics community.

Personalized View Selection of 3D Molecular Proteins

A non-linear classifier is adopted in this chapter to represent the best view for 3D molecule of a protein onto the 2D screen plane. The classifier receives as inputs visual as well as semantic features and actually model the entropy needed to display with high performance the protein. The visual descriptors have been extracted in our case using the OpenCV tookit of the Intel Corporation, while the semantic information includes additional knowledge for the protein. Finally, an XML –based middleware is used to embed complex computer vision algorithms into the contemporary protein viewers which allow only limited transformations on the protein data structure. Experimental results on real-life protein molecules are presented to demonstrate the outperformance of the proposed algorithm.

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