Members of the Computer Graphics Group have participated in the following projects :

Three Dimensional Within-Class Object Retrieval with Applications in Ear Recognition
(GSRT research grant - Joint with CBL, University of Houston, TX)
Principal Investigator (UoA) : T.Theoharis
Principal Investigator (UH) : I. Kakadiaris

PhD Researchers (UoA) : TBD
Budget : € 60.000 (UoA) +
60.000 (UH)

As the size of the available collections of 3D objects grows, data-base like operations become essential for their management, with the key operation being retrieval (query). Large collections are also pre-categorized into classes, so that a single class contains objects of the same type (e.g. human faces). Within-class retrieval methods differ significantly to those for intra class retrieval, since they must provide higher discrimination power. At the same time they can exploit the basic characteristics of the object class. The aim of this research is within-class 3D object retrieval, able to discriminate objects with subtle differences. As testing ground, it is intended to use the biometric field of ear recognition. The three dimensional form of the human ear provides a unique identifying characteristic for humans (like the fingerprint or the face). However it is non-intrusive (in contrast to fingerprint capture) and more reliable than facial scans (the ear is more rigid than the facial region: there are no 'ear expressions'). Ear recognition is a novel biometric at an infant research stage and no significant ear databases exist; for this reason we propose to create an ear database and make it available to the research community. 


Advanced Methods of Visual Computing in Cultural Heritage
(GSRT PENED research grant #70/3/8405 - Joint with IPTHL Thessaloniki)
Principal Investigator (IPTHL) :  M. Strintzis
Principal Investigator (UoA) : T.Theoharis
Senior Researchers (UoA) : G.Papaioannou, V. Drakopoulos, I. Kakadiaris, N. Paragios
PhD Researchers (UoA) : G.Passalis, P.Stavrou, P. Manousopoulos
Budget : € 224.970

This project aims to apply visual computing techniques in the field of cultural heritage. In particular, it aims to reconstruct and visualize cultural entities. This process is divided into four stages: a) 3D object retrieval in digital libraries based on material similarity, age, extracted resemblance (patterns, carvings) or even complementarity of characteristics such as texture or morphology. b) Synthesis (part matching and combination). c) Filling (repair of incomplete surfaces and holes). d) Real time realistic and animated visaulization of the reconstructed object or scene.


Knowledge Rased Retrieval of 3D Models
(GSRT PENED research grant #70/3/8419 - Joint with EKEFE Demokritos)
Principal Investigator (Demokritos) :  S. Perantonis - I. Pratikakis
Principal Investigator (UoA) : T.Theoharis - S. Theodoridis
Senior Researchers (UoA) : V. Drakopoulos
PhD Researchers (UoA) : P. Papadakis
Budget : € 107.400

The main goal is the investigation of novel representation techniques for 3D models with the aim of efficient 3D object retrieval in multimedia databases.

Computer Aided Restoration of Archaeological Monuments using Computer Graphics
(University of Athens research grand #70/4/3241)
Principal Investigators : A.Boehm
Members :  Th.Theoharis, G.Papaioannou, E.A.Karabassi

In this project, an effort was conducted to model and solve the problem of the reconstruction of the archaeological site of Athens' Acropolis with the aid of computer based methods. The aim was not the creation of another tool for a virtual reconstruction of the site based on architectural plans, but the efficient representation of archaeological data (digitized archaeological fragments)  and the development of algorithms for automatic measurement, classification and combination of the available data in order to assist the work of the Acropolis restoration group.
    Part of the work related to the archaeological fragments representation, focuses on the modeling and exploitation of texture information, as described in "G. Papaioannou, T. Theoharis, A. Boehm, A Texture Controller, The Visual Computer, Springer-Verlag, 14(10), pp 488-496, 1998".

Computer Aided Simulation and Graphical Representation of Accumulation Phenomena
(University of Athens research grand #70/4/3241)
Principal Investigators : Th.Theoharis
Members :   E.A.Karabassi, G.Papaioannou

The goal of this project was to study the representation of accumulation phenomena, e.g. accumulation of dust, snow, mud etc. The project follows a "computer graphics approach" of the subject, where the goal is to achieve realistic images incorporating such phenomena, rather than focusing on a simulation from the physicist's point of view. Research was basically conducted on fast and accurate collision detection algorithms between particles and surfaces.
        In most particle systems particle dimensions are very small relative to the remaining objects; therefore collision detection between particles and objects is reduced to simple ray/surface intersection tests. However this is not always a valid assumption : e.g. in cases of materials like slime, mud, or snow the volume of the particles may not be ignored, as this would not only affect physical simulations but could also lead to non-realistic images. In order to study the behavior of such  models, where particles are manipulated as spherical objects of a non negligible volume, we have developed an intersection detection algorithm between spherical particles’ trajectories ( i.e. cylinders with spherical caps ) and polygons. Our algorithm consists of a set of intersection tests between spheres/cylinders and lines/triangles.
The method is discussed in "E.A. Karabassi, G. Papaioannou, Th. Theoharis, Intersection Test for Collision Detection in Particle Systems, ACM Journal of Graphics Tools, (accepted for publication)".

Multiresolutional Editing of Polygon Models
(University of Athens research grand #70/4/4151)
Principal Investigators : F.Tzaferis
Members :  N.Platis

Multiresolution analysis techniques provide efficient ways of displaying complex scenes, by storing multiple levels of detail of the scene and displaying each time only the required amount of detail for visually acceptable results. This project concentrates on multiresolution methods that deal specifically with polygonal models. An interesting extension of these methods is to support multiresolution editing of the models: the user can work in coarse resolutions to change the overall shape of the model, or in more fine resolutions for the details; in any case, the full multiresolution representation of the model must be updated to reflect the changes.
    The project evaluates the existing multiresolution methods for their support of editing. The most suitable ones will be extended as needed and editing will be implemented for the best of them.

Fractals and Dynamic Systems
(University of Athens research grand #70/4/1388)
Principal Investigators :
Members :

Mandelbrot-like Sets of Konig Iteration Functions
(University of Athens research grand #70/4/2403)
Principal Investigators :
Members :

Fractal Interpolation Functions
(University of Athens research grand #70/4/3247)
Principal Investigators :
Members :

Fractal Interpolation Surfaces
(University of Athens research grand #70/4/4160 )
Principal Investigators :
Members :

Computer Graphics Group members : E.A.Karabassi, G.Papaioannou
The objective of the PATRA project is the development and clinical evaluation of an industrial prototype of a system used in cooperation with the existing angiographic equipment (add-on), which will allow the reconstruction, visualization and processing of a 3D model of the cardiac structure under examination. In other words, 3D modeling of the human vascular system. We have developed specifically for this project an angiography processing subsystem named Angioenhancer to semi automatically extract vessel structures from digital angiography data.
PATRA home page

(ESPRIT 24484)
Computer Graphics Group members : G.Papaioannou, E.A.Karabassi
3DHeartView home page