Publications : 2006 conferences
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Publications : 2005 conferences

  Ancient technology works presentation using interaction and gesture recognition
The proposed application aims at the development of a new interactive application for the presentation of Ancient Greek Technology works, with the use of advanced virtual reality and computer vision technologies. The system consists of the haptic interaction system, gesture recognition algorithms, software agents simulating ancient Greek technology mechanisms and the scenario-authoring tool. The components of the system are integrated together through the APEIRO core simulation support unit.
D.Tzovaras, G. Nikolakis, T. Harissis, V. Matsos, K. Tanis, K. Karkaletsis
2nd International Conference on Ancient Greek Technology, Athens, 17-21 October 2005
 
  3D Shape-Based Techniques for Protein Classification
xxx
P. Daras, D. Zarpalas, D. Tzovaras and M.G. Strintzis
IEEE International Conference on Image Processing (ICIP 2005), Genova, Italy, September 2005.
 
  Reduction of Blocking Artifacts in Block-based Compressed Images
xxx
G.A. Triantafyllidis, D. Tzovaras and M.G. Strintzis
Advanced Concepts for Intelligent Vision Systems, Acivs 2005, Antwerp, Belgium, September 2005.
 
  3D Content-Based Search and Retrieval using the 2D Polar Wavelet Transform
In this paper, the 2D Polar Wavelet Transform is
proposed for content based search and retrieval of 3D objects.
After the decomposition of a 3D object’s volume into a set of
planes, the 2D Polar Wavelet Transform is applied to each of
them, generating a set of 2D rotation invariant features. These
features comprise the input to the Spherical Trace Transform
for the final descriptor extraction, which will be used for
the shape matching. The 2D Wavelet Transform demonstrated
experimentally a high discriminative power, as compared to other
existing methods.
A. Axenopoulos, P. Daras, D. Zarpalas, D. Tzovaras and M.G. Strintzis
IEEE International Conference on Image Processing (ICIP 2005), Genova, Italy, September 2005.
 
  VRLAB: Remote Experiment Laboratories using Virtual Reality Technologies: The VRLab Project
xxx
A. Tsakiris, I. Filippidis,N. Grammalidis,D. Tzovaras and M. G. Strintzis
ICTAMI-International Conference on Theory and Applications in Mathematics and Informatics, Alba Lulia,Romania, September 2005.
 
  Remote Experiment Laboratories using Virtual Reality Technologies: The VRLab Project
xxx
A. Tsakiris, I. Filippidis,N. Grammalidis,D. Tzovaras and M. G. Strintzis
ICTAMI-International Conference on Theory and Applications in Mathematics and Informatics, Alba Lulia,Romania, September 2005.
 
  CANE SIMULATION FOR THE BLIND
xxx
G. Nikolakis, D. Tzovaras, M. G. Strintzis
13th European Signal Processing Conference (EUSIPCO2005), Antalya, Turkey, September 2005.
 
  TEXT-TO-SIGN LANGUAGE SYNTHESIS TOOL
xxx
M. Papadogiorgaki, N. Grammalidis, D. Tzovaras, M. G. Strintzis
13th European Signal Processing Conference (EUSIPCO2005), Antalya, Turkey, September 2005.
 
  OBJECT RECOGNITION FOR THE BLIND
xxx
G. Nikolakis, D. Tzovaras, M. G. Strintzis
13th European Signal Processing Conference (EUSIPCO2005), Antalya, Turkey, September 2005.
 
  Reliving VE Day with Activated Schemata
xxx
P. Turner, S. Turner and D. Tzovaras
In M. Slater (Ed.) Proc. 8 th International Workshop on Presence . London, 21st - 23rd September 2005
 
  MASTER-PIECE: A Multimodal (Gesture+Speech) Interface for 3D Model Search and Retrieval Integrated in a Virtual Assembly Application
The ”MASTER-PIECE” (Multimodal Assembly with SIMILAR Technologies from European Research utilizing a Personal Interface in an Enhanced Collaborative Environment) project aims at the generation of a multimodal interface using gesture and speech in order to manipulate a virtual assembly application. Besides assembling mechanical objects, the user is capable to perform 3D model content based search in a database of 3D objects using as query model a scene object. Finally, to deal with cases where no query model is available, a sketch based approach is proposed which results in the manual approximate generation of the query model. More specifically, the user can draw a specific number of primitive objects by moving his/her hands and then process-combine them so as to build more complex shapes, which are finally used as query models. Experimental results illustrate that the proposed scheme enhances significantly the realism of the interaction, while using the sketch-based approach the user can search for 3D objects in the database without the need of an initial query object, which is the case in most state of the art approaches.
K. Moustakas, D. Tzovaras, S. Carbini, O. Bernier, J.E. Viallet, S. Raidt, M. Mancas, M.Dimiccoli,
E. Yagci, S. Balci and E.I. Leon
In Proceedings of Summer Workshop on Multimodal Interfaces eNTERFACE 2005, August 2005
 
  Enhancing Electronic Music Tuition Systems with Virtual Reality Tools
xxx
D. Koutsonanos, M. Papadogiorgaki, E. Kalapanidas, D. Tzovaras, C.Davarakis and M.G.Strintzis
5th Open Workshop of MUSICNETWORK: Integration of Music in Multimedia Applications, Vienna, Austria, July 2005.
 
  Enhancing Costume designer Creativity Utilizing Haptic Interaction in Cloth Editing Applications
In this paper a novel framework for editing and simulating cloth over animated characters is presented. The core of the proposed animator is an hierarchical cloth simulation scheme, which manages to reduce the computational complexity of the implicit integration without loosing in accuracy. Further, the user of the presented application is capable of interacting with the virtual environment using 6DOF haptic devices. He is able to perform fitting operations as well as to alter the structure of the mesh, thus creating alternative versions of a single mesh. The cloth editing and simulation procedures are integrated onto a cloth editing application so as to ensure stability. Evaluation of the proposed framework showed that the system is efficient, easy to use and realistic.

K. Moustakas, D. Koutsonanos, D. Tzovaras and M.G.Strintzis
11th International Conference on Human-Computer Interaction (HCI 2005),
Las Vegas, Nevada USA, July 2005

 
  Ancient Technology Works Presentation Using Haptic Interaction and Gesture Recognition
The proposed application aims at the development of a new interactive application for the presentation of Ancient Greek Technology works, with the use of advanced virtual reality and computer vision technologies. The system consists of the haptic interaction system, gesture recognition algorithms, software agents simulating ancient Greek technology mechanisms and the scenario-authoring tool. The components of the system are integrated together through the APEIRO core simulation support unit.
G.Nikolakis, D.Tzovaras, S.Malassiotis and M.G.Strintzis
11th International Conference on Human-Computer Interaction (HCI 2005),
Las Vegas, Nevada USA, July 2005
 
  Haptic Representation of Images for the Blind and the Visually Impaired
This work aims at the creation of an interactive environment in order to allow blind people to perceive gray scale images. Image processing techniques are used in order to extract information from the images and convert it into haptic representation. To achieve these conversions the technical limitations of the haptic device as well as the ability of the users to perceive haptic information is taken into account. Two methods are proposed using spatial and kinesthetic information.
G.Nikolakis, K.Moustakas, D.Tzovaras and M.G.Strintzis
11th International Conference on Human-Computer Interaction (HCI 2005),
Las Vegas, Nevada USA, July 2005
 
  Haptic Interaction with a Virtual Environment Dynamically Created from a Monoscopic Video
The present paper presents a novel framework for haptic interaction with 3D virtual scenes, which are generated from a monoscopic video. Initially, a bi-directional 2D motion estimation is performed on the video, which is followed by an efficient method for reliably tracking object contours. Rigid 3D motion and structure is recovered utilizing extended Kalman filtering. The resulting 3D structure data are used to generate the 3D model of the processed scene. This is accomplished either by generating a single mesh of the scene utilizing the generated depth maps, or by applying superquadric approximation and modeling for the objects of the scene using analytical implicit functions. The generated model is used in order to provide haptic access to the processed scene for the blind. Experimental evaluation demonstrates the usability of the proposed methods, especially when used to train visually impaired people in simple 3D virtual environments.
K.Moustakas, G.Nikolakis, D.Tzovaras and M.G.Strintzis
11th International Conference on Human-Computer Interaction (HCI 2005),
Las Vegas, Nevada USA, July 2005
 
  Protein Matching using Geometrical Characteristics
xxx
P. Daras, D. Zarpalas, D. Tzovaras and M. G.Strintzis
6th International Workshop on Image Analysis for Multimedia Interactive Services (WIAMIS 2005), Montreux, Switzerland, April 2005.
 
  3D Model Search and Retrieval Based on Fourier Transforms
xxx
D. Zarpalas, P. Daras, D. Tzovaras and M. G.Strintzis
6th International Workshop on Image Analysis for Multimedia Interactive Services (WIAMIS 2005), Montreux, Switzerland, April 2005.
 
  3D Object Retrieval Using 3D Packet Wavelet Transform and Knowledge Interpretation
xxx
A. Axenopoulos, P. Daras, D. Tzovaras and M. G. Strintzis
6th International Workshop on Image Analysis for Multimedia Interactive Services (WIAMIS 2005), Montreux, Switzerland, April 2005.
 
  Classification of 3D Models using Combined Semantical and Geometrical Information
The present paper proposes a novel framework for the classification of 3D objects into specific categories using semantic information combined with geometrical characteristics. During the modeling phase an ontology is constructed with instances for each class of objects (animals, humans etc.), which contain semantic information about the parts constituting them. Geometric descriptors are then assigned to each part. During the recognition phase, the objects are segmented and geometrical descriptors are extracted for each segment. Finally, these geometric descriptors are compared to the descriptors of each of the instance parts, dissimilarity metrics are calculated and the object is classified to the class, which minimizes this metric. Experimental evaluation demonstrates that the proposed approach overcomes major problems that arise when objects are treated as a whole and when only geometric characteristics are taken into account.
K. Moustakas, P. Daras, D. Tzovaras and M.G. Strintzis
First International Workshop Towards Semantic Virtual Environments (SVE2005)
Villars, Switzerland, March 2005
 
  Haptic Feedback Using an Efficient Superquadric Based Collision Detection Method
The present paper proposes an efficient collision detection algorithm suitable for use in haptic applications. The method exploits the fact that the virtual hand can be modelled once and then be used in a variety of applications. In particular, it models each segment of the virtual hand using superquadrics. In order to resolve collision queries the only test that has to be performed is the evaluation of the superquadric inside outside function for each superquadric segment. Experimental evaluation illustrates that the proposed method is extremely fast when compared to standard mesh based approaches. Moreover, it is more realistic and provides the possibility of resolving collision queries for the whole hand and not only for the fingertips, which is the case for methods using spheres at the fingertips in order to perform collision detection. The force feedback provided to the user through the haptic devices is directly evaluated using the analytical formulae of the superquadrics. Finally, two virtual reality applications, which use the proposed method are presented. Results have shown that the algorithm performed accurately and robustly.
K.Moustakas, G.Nikolakis, D. Koutsonanos, D.Tzovaras and M.G.Strintzis
First Joint Eurohaptics Conference and Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems, Pisa, Italy, March 2005
 
  A Geometry Education Haptic VR Application Based on a New Virtual Hand Representation
The present paper describes an enhanced haptic virtual reality application for geometry education. The proposed application allows the user to create and edit a scene that consists of three-dimensional geometrical objects in order to form and solve complex geometrical problems. The core of the proposed scheme is based on a novel interference detection algorithm, which utilizes implicit surfaces, such as superquadrics, and their analytical description to speed up collision detection between the virtual hand and the virtual environment. Intersection tests are executed utilizing the implicit analytical formulae of the superquadrics. Experimental results demonstrate the high applicability of the proposed application and the huge gain in speed of the proposed collision detection approach when compared to state of the art methods.
K.Moustakas, G.Nikolakis, D.Tzovaras and M.G.Strintzis
IEEE VR2005, Bonn, Germany, March 2005.
Publications : 2004 conferences
  Simulation of Ancient Technology Works Using Haptic Interaction and Gesture Recognition
The objective of the proposed application is the development of a new interactive application for the simulation of Ancient Greek Technology works, with the use of advanced virtual reality and computer vision technologies. In order to achieve these objectives haptic interaction mechanisms and a gesture recognition system were implemented in a virtual environment platform. A novel collision detection method was developed and virtual reality agents were used in order to achieve the desired results. The developed system was evaluated by real users and conclusions were drawn concerning the potentiality of the proposed application.
G. Nikolakis, D. Tzovaras, S. Malassiotis and M. G. Strintzis
5th International Symposium on Virtual Reality, Archaeology and Cultural Heritage (Eurographics)
Brussels, Belgium, December 2004
 
  Interactive Cloth Editing and Simulation in Virtual Reality Applications for Theater Professionals
This paper presents an efficient framework for the interactive simulation and editing of clothing over avatars. Specifically, a very efficient costume designer application is proposed based on new developments in cloth modeling simulation and animation. To animate cloth an hierarchical simulator is used, which speeds up the simulation without loosing in accuracy. Enhanced interaction potentiality is provided to the application user, using haptic devices with 6DOF for interaction. Furthermore, the user is capable of editing the cloth mesh, thus generating alternative versions of it, which could be more appropriate for a costume designer application. The mesh editing is performed so as to assure the stability of the simulation and the realism of the application. In order to validate the usability of our application, a number of case studies were conducted, which showed that the present system is efficient, user friendly and realistic.
D. Koutsonanos, K. Moustakas , D. Tzovaras and M. G. Strintzis
5th International Symposium on Virtual Reality, Archaeology and Cultural Heritage (Eurographics)
Brussels, Belgium, December 2004
 
  3D Model Search and Retrieval Based on the Spherical Trace Transform
xxx
P.Daras, D.Zarpalas, D.Tzovaras and M.G.Strintzis
IEEE International Workshop on Multimedia Signal Processing (MMSP 2004), Siena, Italy, October 2004
 
  Optimal Hierarchical Representation and Simulation of Cloth and Deformable Objects
This paper presents a novel pyramidal representation scheme for deformable object modelling, which uses a hierarchical approach to optimize the system's performance by executing the simulation in every level of a pyramid. The simulation results of each level are used to predict the lower level's state. The prediction is used as initial guess for the simulation of the lower level. The above procedure is repeated until the final level is reached. Experimental evaluation demonstrates that the proposed scheme is able to reduce significantly the computational cost, especially when the simulation involves procedures, which need large numerical computation like the Conjugate Gradient in implicit integration schemes.
K. Moustakas , D. Tzovaras and M. G. Strintzis
IEEE International Conference on Image Processing (ICIP 2004), Singapore , October 2004
 
  Watermarking 3D Models for Data Hiding
A novel method for the watermarking of3D models is proposed, which is robust to geometric distortions such as rotation, translation and uniform scaling. After proper positioning and alignment of the 31) models, a watermark is embedded in the vertices of the model using a rohust technique for modifying imperccptibly thc location of a subset
of the 3D model vertices. The watermark can be used as a link to an idcntifier for the 3D model and the entire system can be used for data hiding applications. One application
is the use of watermark as a link to 3D model descriptors for content-based search and retrieval. Experimental results show the ability of the proposed method to aforementioned
attacks. The proposcd method is also rohust against vertex reordering attack.
P.Daras, D.Zarpalas, D.Tzovaras and M.G.Strintzis
IEEE International Conference on Image Processing (ICIP 2004), Singapore , October 2004
 
  CyberGrasp and PHANTOM Integration: Enhanced Haptic Access for Visually Impaired Users
This paper presents a haptic virtual reality tool developed to enhance the accessibility for the visually impaired. The proposed approach focuses on the development of a highly interactive haptic virtual reality system that allows visually impaired, to study and interact with various virtual objects in specially designed virtual environments. The system is based on the use of the CyberGrasp™ and the PHANToM™ haptic devices. A number of custom applications have been developed based on object recognition and manipulation, and utilizing the advantages of both haptic devices. The system has been tested and evaluated in three custom training applications for the visually impaired.
G. Nikolakis, D. Tzovaras, S. Moustakidis and M. G. Strintzis
9th International Conference Speech and Computer (SPECOM'2004)
St Petersbourg, Russia, September 2004
 
  Haptic Browser: A Haptic Environment to Access HTML Pages
The application presented in this paper aims at producing a novel user-friendly haptic environment to allow blind or visually impaired people to access interactive presentations based on HTML web pages. The application is based on haptic and audio feedback. Additionally, an automatic HTML-to-haptics conversion tool is developed in order provide a simple way to create interactive haptic presentations and a text to speech tool is used in order to create audio descriptions for the web pages. The environment has been evaluated using three presentations that were associated to computer access and useage. According to the users feedback the application was characterized as very useful.
G. Nikolakis, I. Tsampoulatidis, D. Tzovaras and M. G. Strintzis
9th International Conference Speech and Computer (SPECOM'2004)
St Petersbourg, Russia, September 2004
 
  A Non Causal Bayesian Framework for Object Tracking and Occlusion Handling
for the Synthesis of Stereoscopic Video
This paper presents a framework for the synthesis of stereoscopic video using as input only a monoscopic image sequence. Initially, bi-directional 2D motion estimation is performed, which is followed by an efficient method for the reliable tracking of object contours. Rigid 3D motion and structure is recovered utilizing extended Kalman filtering. Finally, occlusions are dealt with a novel Bayesian framework, which exploits future information to correctly reconstruct occluded areas.
Experimental evaluation shows that the layered object scene representation, combined with the proposed methods for object tracking throughout the sequence and occlusion handling, yields very accurate results.
K. Moustakas , D. Tzovaras and M. G. Strintzis
2nd International Symposium on 3D Data Processing, Visualization, and Transmission (3DPVT 2004)
Thessaloniki, Greece, September 2004
 
  Shape Matching Using the 3D Radon Transform
In this paper a novel method for 3D model content-based search and retrieval based on the 3D Radon Transform and a querying-by-3D-model approach, is presented. Descriptors are extracted using the 3D Radon Transform and applying a set of functionals on the transform coefficients. Similarity measures are then created for the extracted descriptors and introduced into a 3D model-matching algorithm. This results to a very fast and accurate matching method. Experiments were performed using two different databases and comparing the proposed method with others. Experimental results show that the proposed method can be used for 3D model search and retrieval in a highly efficient manner.
P.Daras, D.Zarpalas, D.Tzovaras and M.G.Strintzis
3D Data Processing, Visualization & Transmission (3DPVT 2004), Thessaloniki, September 2004.
 
  3D Model Watermarking for Indexing Using the Generalized Radon Transform
XXX
P.Daras, D.Zarpalas, D.Tzovaras and M.G.Strintzis
3D Data Processing, Visualization & Transmission (3DPVT 2004), Thessaloniki, September 2004.
 
  Extraction of 3D Scene Structure from a Video for the Generation of 3D Visual and Haptic Representations
Our work in this paper deals with the incorporation of multimodal interfaces for establishing new applications for special population categories. Specifically, the present work focuses on the integration of information originating from two main modalities, i.e. video and haptics for two very innovative applications, namely:
• a virtual reality environment for controlling and monitoring a remote ultrasound examination (utilizing video data and haptic feedback).
• a haptic representation of a real 3D scene for providing access to the blind and visually impaired to real life scenarios.
The innovative aspect of the proposed approach is the integration and synchronization of two completely complementary modalities, i.e. haptics and video. In order to synchronize them, video information is used by a novel structure from motion algorithm in order to extract a 3D representation of the captured scene which is then provided as input to the haptic interaction system.
K. Moustakas , G. Nikolakis, D. Tzovaras and M. G. Strintzis
Workshop on Multimodal Interaction (W3C 2004) Sophia Antipolis, France , July 2004
 
  Fast Hierarchical Simulation of Cloth and Deformable Objects using an Optimal Pyramidal Representation
This paper presents a novel pyramidal representation scheme for deformable object modelling, which uses a hierarchical approach to optimize the system's performance by executing the simulation in every level of a pyramid utilizing the forces of the original mesh. The simulation results of each level are used to predict the lower level's state, using an optimal filtering procedure. The prediction is used as initial guess for the simulation of the lower level. The above procedure is repeated until the final level is reached. Experimental evaluation demonstrates that the proposed scheme is able to reduce significantly the computational cost, especially when the simulation involves procedures, which need large numerical computation like the Conjugate Gradient in implicit integration schemes.
K. Moustakas , D. Tzovaras and M. G. Strintzis
Computer Animation and Social Agents Conference (CASA 2004), Geneva, Switzerland, July 2004
 
  Ontology Based Interactive Graphic Environment for Product Presentation
This paper proposes an innovative environment for presenting products through the Internet using modern visualization techniques and providing high level of interaction with the user. The environment consists of three main modules, namely :
a) the scene-authoring tool,
b) the interactive scene-viewer
c) the assembly-demonstration tool.
These modules are bound together with the utilization of a robust ontology-based knowledge management system.
I. Tsampoulatidis, G. Nikolakis, D. Tzovaras and M. G. Strintzis
Computer Graphics International (CGI 2004), Crete, Greece, June 2004
 
  3D Model Search and Retrieval Based on the 3D Radon Transform
This paper describes a novel method for 3D model content-based search and retrieval based on the 3D Radon Transform and a querying-by-3D-model approach. Descriptors are extracted using the 3D Radon Transform and applying a number of functionals on the transform’s coefficients. Similarity measures are then created for the extracted descriptors and introduced into a 3D model-matching algorithm. This results to a very fast and accurate matching method. Experimental results are presented evaluating the performance of the proposed method in terms of precision versus recall diagrams
D.Zarpalas, P.Daras, D.Tzovaras and M.G.Strintzis
International Conference on Communications (ICC-2004), Multimedia Technologies and Services Symposium (MMTS), Paris, France, June 2004.
 
  A Mixed Reality Learning Environment for Geometry Education
xxx
G. Nikolakis, G. Fergadis, D. Tzovaras and M.G. Strintzis
Setn 04 Proc. Samos, May 2004.
 
  Generalized Radon Transform Based 3D Feature Extraction for 3D Object C classification
xxx

P.Daras, D.Zarpalas, D.Tzovaras and M.G.Strintzis

5th International Workshop on Image Analysis for Multimedia Interactive Services (WIAMIS 2004), Lisboa, Portugal, April 2004.
Publications : 2004 conferences
  Simulation of Ancient Technology Works Using Haptic Interaction and Gesture Recognition
The objective of the proposed application is the development of a new interactive application for the simulation of Ancient Greek Technology works, with the use of advanced virtual reality and computer vision technologies. In order to achieve these objectives haptic interaction mechanisms and a gesture recognition system were implemented in a virtual environment platform. A novel collision detection method was developed and virtual reality agents were used in order to achieve the desired results. The developed system was evaluated by real users and conclusions were drawn concerning the potentiality of the proposed application.
G. Nikolakis, D. Tzovaras, S. Malassiotis and M. G. Strintzis
5th International Symposium on Virtual Reality, Archaeology and Cultural Heritage (Eurographics)
Brussels, Belgium, December 2004
 
  Interactive Cloth Editing and Simulation in Virtual Reality Applications for Theater Professionals
This paper presents an efficient framework for the interactive simulation and editing of clothing over avatars. Specifically, a very efficient costume designer application is proposed based on new developments in cloth modeling simulation and animation. To animate cloth an hierarchical simulator is used, which speeds up the simulation without loosing in accuracy. Enhanced interaction potentiality is provided to the application user, using haptic devices with 6DOF for interaction. Furthermore, the user is capable of editing the cloth mesh, thus generating alternative versions of it, which could be more appropriate for a costume designer application. The mesh editing is performed so as to assure the stability of the simulation and the realism of the application. In order to validate the usability of our application, a number of case studies were conducted, which showed that the present system is efficient, user friendly and realistic.
D. Koutsonanos, K. Moustakas , D. Tzovaras and M. G. Strintzis
5th International Symposium on Virtual Reality, Archaeology and Cultural Heritage (Eurographics)
Brussels, Belgium, December 2004
 
  3D Model Search and Retrieval Based on the Spherical Trace Transform
This paper presents a novel approach oin 3D content based search and retrieval. First, a set of functionals are applied an a 3D model's volume producing a new domain a new set of concentric spheres.In this new domain a new set of functionals is applied, resulting to a completely rotation invariant descriptor vector,which is used for 3Dmodel matching.Experiments were performed using a database and comparing the proposed method with the MPEG-7 3D Shape Spectrum descriptor.Experimental results show that the proposed method is superior in terms of precision versus recall and can be used for 3D model search and retrieval in ahighly efficient manner.
P.Daras, D.Zarpalas, D.Tzovaras and M.G.Strintzis
IEEE International Workshop on Multimedia Signal Processing (MMSP 2004), Siena, Italy, October 2004
 
  Optimal Hierarchical Representation and Simulation of Cloth and Deformable Objects
This paper presents a novel pyramidal representation scheme for deformable object modelling, which uses a hierarchical approach to optimize the system's performance by executing the simulation in every level of a pyramid. The simulation results of each level are used to predict the lower level's state. The prediction is used as initial guess for the simulation of the lower level. The above procedure is repeated until the final level is reached. Experimental evaluation demonstrates that the proposed scheme is able to reduce significantly the computational cost, especially when the simulation involves procedures, which need large numerical computation like the Conjugate Gradient in implicit integration schemes.
K. Moustakas , D. Tzovaras and M. G. Strintzis
IEEE International Conference on Image Processing (ICIP 2004), Singapore , October 2004
 
  Watermarking 3D Models for Data Hiding
xxx
P.Daras, D.Zarpalas, D.Tzovaras and M.G.Strintzis
IEEE International Conference on Image Processing (ICIP 2004), Singapore , October 2004
 
  CyberGrasp and PHANTOM Integration: Enhanced Haptic Access for Visually Impaired Users
This paper presents a haptic virtual reality tool developed to enhance the accessibility for the visually impaired. The proposed approach focuses on the development of a highly interactive haptic virtual reality system that allows visually impaired, to study and interact with various virtual objects in specially designed virtual environments. The system is based on the use of the CyberGrasp™ and the PHANToM™ haptic devices. A number of custom applications have been developed based on object recognition and manipulation, and utilizing the advantages of both haptic devices. The system has been tested and evaluated in three custom training applications for the visually impaired.
G. Nikolakis, D. Tzovaras, S. Moustakidis and M. G. Strintzis
9th International Conference Speech and Computer (SPECOM'2004)
St Petersbourg, Russia, September 2004
 
  Haptic Browser: A Haptic Environment to Access HTML Pages
The application presented in this paper aims at producing a novel user-friendly haptic environment to allow blind or visually impaired people to access interactive presentations based on HTML web pages. The application is based on haptic and audio feedback. Additionally, an automatic HTML-to-haptics conversion tool is developed in order provide a simple way to create interactive haptic presentations and a text to speech tool is used in order to create audio descriptions for the web pages. The environment has been evaluated using three presentations that were associated to computer access and useage. According to the users feedback the application was characterized as very useful.
G. Nikolakis, I. Tsampoulatidis, D. Tzovaras and M. G. Strintzis
9th International Conference Speech and Computer (SPECOM'2004)
St Petersbourg, Russia, September 2004
 
  A Non Causal Bayesian Framework for Object Tracking and Occlusion Handling
for the Synthesis of Stereoscopic Video
This paper presents a framework for the synthesis of stereoscopic video using as input only a monoscopic image sequence. Initially, bi-directional 2D motion estimation is performed, which is followed by an efficient method for the reliable tracking of object contours. Rigid 3D motion and structure is recovered utilizing extended Kalman filtering. Finally, occlusions are dealt with a novel Bayesian framework, which exploits future information to correctly reconstruct occluded areas.
Experimental evaluation shows that the layered object scene representation, combined with the proposed methods for object tracking throughout the sequence and occlusion handling, yields very accurate results.
K. Moustakas , D. Tzovaras and M. G. Strintzis
2nd International Symposium on 3D Data Processing, Visualization, and Transmission (3DPVT 2004)
Thessaloniki, Greece, September 2004
 
  Shape Matching Using the 3D Radon Transform
xxx
P.Daras, D.Zarpalas, D.Tzovaras and M.G.Strintzis
3D Data Processing, Visualization & Transmission (3DPVT 2004), Thessaloniki, September 2004.
 
-   3D Model Watermarking for Indexing Using the Generalized Radon Transform
The present paper proposes a novel method for 3D-model watermarking for indexing. The proposed approach is based on the use of a Generalized Radon Transformation. More specifically, the Cylindrical Integration Transform (CIT) is initially applied to the 3D models in order to produce descriptor vectors. At the same time a watermarking technique, based on CIT is used in order to embed a specific model identifier in the nodes of the 3D model. This identifier links the model to its descriptor vector, which is extracted only once and stored in a database. Every time this model is employed as a query model, watermark detection is used so as to retrieve the corresponding identifier and further the descriptor vector, which can be further used in a matching algorithm. The proposed techniques are evaluated experimentally in terms of both watermarking efficiency and content-based retrieval performance.
P.Daras, D.Zarpalas, D.Tzovaras and M.G.Strintzis
3D Data Processing, Visualization & Transmission (3DPVT 2004), Thessaloniki, September 2004.
 
  Extraction of 3D Scene Structure from a Video for the Generation of 3D Visual and Haptic Representations
Our work in this paper deals with the incorporation of multimodal interfaces for establishing new applications for special population categories. Specifically, the present work focuses on the integration of information originating from two main modalities, i.e. video and haptics for two very innovative applications, namely:
• a virtual reality environment for controlling and monitoring a remote ultrasound examination (utilizing video data and haptic feedback).
• a haptic representation of a real 3D scene for providing access to the blind and visually impaired to real life scenarios.
The innovative aspect of the proposed approach is the integration and synchronization of two completely complementary modalities, i.e. haptics and video. In order to synchronize them, video information is used by a novel structure from motion algorithm in order to extract a 3D representation of the captured scene which is then provided as input to the haptic interaction system.
K. Moustakas , G. Nikolakis, D. Tzovaras and M. G. Strintzis
Workshop on Multimodal Interaction (W3C 2004) Sophia Antipolis, France , July 2004
 
  Fast Hierarchical Simulation of Cloth and Deformable Objects using an Optimal Pyramidal Representation
This paper presents a novel pyramidal representation scheme for deformable object modelling, which uses a hierarchical approach to optimize the system's performance by executing the simulation in every level of a pyramid utilizing the forces of the original mesh. The simulation results of each level are used to predict the lower level's state, using an optimal filtering procedure. The prediction is used as initial guess for the simulation of the lower level. The above procedure is repeated until the final level is reached. Experimental evaluation demonstrates that the proposed scheme is able to reduce significantly the computational cost, especially when the simulation involves procedures, which need large numerical computation like the Conjugate Gradient in implicit integration schemes.
K. Moustakas , D. Tzovaras and M. G. Strintzis
Computer Animation and Social Agents Conference (CASA 2004), Geneva, Switzerland, July 2004
 
  Ontology Based Interactive Graphic Environment for Product Presentation
This paper proposes an innovative environment for presenting products through the Internet using modern visualization techniques and providing high level of interaction with the user. The environment consists of three main modules, namely :
a) the scene-authoring tool,
b) the interactive scene-viewer
c) the assembly-demonstration tool.
These modules are bound together with the utilization of a robust ontology-based knowledge management system.
I. Tsampoulatidis, G. Nikolakis, D. Tzovaras and M. G. Strintzis
Computer Graphics International (CGI 2004), Crete, Greece, June 2004
 
  3D Model Search and Retrieval Based on the 3D Radon Transform
xxx
D.Zarpalas, P.Daras, D.Tzovaras and M.G.Strintzis
International Conference on Communications (ICC-2004), Multimedia Technologies and Services Symposium (MMTS), Paris, France, June 2004.
 
  A Mixed Reality Learning Environment for Geometry Education
xxx
G. Nikolakis, G. Fergadis, D. Tzovaras and M.G. Strintzis
Setn 04 Proc. Samos, May 2004.
 
  Generalized Radon Transform Based 3D Feature Extraction for 3D Object C classification
xxx

P.Daras, D.Zarpalas, D.Tzovaras and M.G.Strintzis

5th International Workshop on Image Analysis for Multimedia Interactive Services (WIAMIS 2004), Lisboa, Portugal, April 2004.
 

Publications : 2003 conferences
  Stereoscopic Video Authoring Tool based on Efficient Object-based Structure and Motion Estimation from a Monoscopic Image Sequence

This paper presents a novel object-based method for the generation of a stereoscopic image sequence from a monoscopic video, using bi-directionnal 2D motion estimation and rigid motion and structure recovery. The latter is based on extended Karman filters and an efficient method for reliably tracking object masks. An authoring tool is also presented, which provides a number of user intervention utilities to assist the efficient computer vision methods proposed. Experimental results show that the layered object representation for the scene combined with the proposed algorithm, for reliably tracking object masks throughrout the sequence, yields very accurate results.

K. Moustakas, D. Tzovaras and M.G.Strintzis
2nd International Workshop on ICTs, Arts and Cultural Heritage, Athens, Greece, October 2003
 
  Virtual Assembly Based on Stereo Vision and Haptic Force Feedback Virtual Reality
This paper presents the virtual reality application developed for the project called “A Virtual Assembly Environment for Industrial Planning” funded by General Secretariat for Research and Technology of Greece. The project aims at developing a highly interactive and extensible haptic VR system that allows the user to study and interact with various virtual objects and perform assembly planning in the virtual environment. An application has been developed based on the interface provided by the CyberTouch™ and the CyberGrasp ™ force feedback haptic devices. The main objective of this paper was to develop a complete assembly planning system for industrial applications based on force feedback haptic interaction techniques in simulated virtual reality environments. The challenging aspect of the proposed VR system is that of addressing visual and haptic feedback to the end user in order to emulate realistic assembly conditions.

G. Nikolakis, G. Fergadis and D. Tzovaras
10th International Conference on Human-Computer Interaction (HCI 2003), Crete, Greece, June 2003

 
  A User Interface Environment in Mobile Tele-echography
xxx

S.Kyratzi, C.Collyda, G.Nikolakis, G.A.Triantafyllidis, D.Tzovaras, P.Daras and M.G.Strintzis

Proc. International Academic Conference on eHealth Telemedicine and Telecare, TELEMED 03, London, January 2003.
Publications : 2002 conferences
  Detection of Occlusion and Visible Background and Foreground Areas in Stereo Image Pairs
xxx
G.A.Triantafyllidis, D.Tzovaras and M.G.Strintzis
International IEEE Conference on Electronics, Circuits and Systems, ICECS 2002, Dubrovnik, Croatia, September 2002.
 
  Image compression for indexing based on the encoding cost map
xxx
D. Simitopoulos, D. Tzovaras, M. G. Strintzis
11th European Signal Processing Conference (EUSIPCO 2002), Toulouse, France, Vol. III, pp. Sep. 2002.
 
  A Hybrid Algorithm for the removal of Blocking Artifacts
xxx
G.A.Triantafyllidis, D.Tzovaras, D.Sampson and M.G.Strintzis
Proc. of the IEEE International Conference on Multimedia and Expo, pp. 161-164, Lausanne, Switzerland, August 2002.
 
  A Neural Network Algorithm for Rigid 3D Motion Estimation from Multiview Image Sequences
xxx
N.Ploskas, D.Tzovaras, G.A.Triantafyllidis and M.G.Strintzis
International Conference on Artificial Neural Networks ICANN 2002, Madrid, Spain, August 2002
 
  Generation of Stereoscopic Image Sequences Using Structure and Rigid Motion Estimation By Extended Kalman Filters
xxx
S. Diplaris, N. Grammalidis, D. Tzovaras and M.G. Strintzis
IEEE International Conference on Multimedia and Expo, Lausanne, Switzerland, August 2002.
 
  Blockiness Reduction in JPEG Coded Images
xxx
G.A.Triantafyllidis, D.Sampson, D.Tzovaras and M.G.Strintzis
14th International Conference on Digital Signal Processing, pp. 1325-1328, Santorini, Greece, July 2002.
 
  Design and Implementation of Virtual Environments for Training of the Visually Impaired
This paper presents the virtual reality applications developed for the feasibility study tests of the EU funded IST project ENORASI. ENORASI aims at developing a highly interactive and extensible haptic VR training system that allows visually impaired people, especially those blind from birth, to study and interact with various virtual objects. A number of custom applications have been developed based on the interface provided by the CyberGrasp haptic device. Eight test categories were identified and corresponding tests were developed for each category. Twenty-six blind persons conducted the tests and the evaluation results have shown the degree of acceptance of the technology and the feasibility of the proposed approach.

D. Tzovaras, G. Nikolakis, G. Fergadis, S. Malasiotis and M. Stavrakis
Fifth International ACM SIGCAPH Conference on Assistive Technologies (ASSETS 2002)
Edinburgh, Scotland, June 2002

 
  Feasibility Study of a Human-Computer Interaction System for the Training of Visually Impaired
The present paper presents a custom human-computer interaction application for the blind, developed for the feasibility study test performed in the Informatics and Telematics Institute for the EU IST project ENORASI. ENORASI aims at developing a highly interactive and extensible haptic virtual reality (VR) system that allows visually impaired people, especially those blind from birth, to study and interact with various virtual objects.
For this purpose we have developed a number of custom applications to support the communication with the CyberGrasp haptic device. Eight test categories were identified and corresponding tests were developed for each category. 26 persons conducted the tests and the results were evaluated. An appropriate evaluation methodology was set up for analyzing test results.
D. Tzovaras, G. Nikolakis, G. Fergadis, S. Malassiotis and M. Stavrakis
Second Hellenic Conference on Artificial Intelligence (SETN 2002), Thessaloniki, Greece, April 2002
 
  Virtual Environments for the Training of Visually Impaired
xxx
D. Tzovaras, G. Nikolakis, G. Fergadis, S. Malassiotis and M. Stavrakis
CUWATTS Conference, Cambridge, March 2002, pp. 151-160
 
  An Efficient Neural Network Approach for Rigid and Non-Rigid 3D Motion Estimation from Multiview Image Sequences
xxx
N.Ploskas, D.Tzovaras, G.A.Triantafyllidis and M.G.Strntzis
Neuro Fuzzy Technologies Congress, Cuba, January 2002.

Publications : 2001 conferences


WAP-based Personalised Health Care Services
S.Petsas, D.Tzovaras, L.Makris and M.G.Strintzis
Conference of the IEEE Engineering in Medicine and Biology (EMBC 2001), Istanbul, Turkey, October 2001.

Coding for the transmission of 3D Medical Images
D.Tzovaras, N.Grammalidis, S.Malassiotis and M.G.Strintzis
International Conference of Image Processing, ICIP' 01, Thessaloniki, Greece, October 2001.

Fast Content-Based Search of VRML Models based on Shape Descriptions
I.Kolonias, D.Tzovaras, S.Malassiotis and M.G.Strintzis
International Conference of Image Processing, ICIP' 01, Thessaloniki, Greece, October 2001.

Blocking Artifact Reduction in Frequency Domain
G.A.Triantafyllidis, D.Tzovaras and M.G.Strintzis
IEEE International Conference on Image Processing ICIP, Thessaloniki, Greece, October 2001.

Detection of Blocking Artifacts of Compressed Still Images
G.A.Triantafyllidis, D.Tzovaras and M.G.Strintzis
11th International Conference on Image Analysis and Processing, Palermo, Italy, September 2001.

A Novel Algorithm for Blockiness Reduction
G.A.Triantafyllidis, D.Tzovaras and M.G.Strintzis
EURASIP Conference on Digital Signal Processing for Multimedia Communications and Services, Budapest, Hungary, September 2001.

A Transform Domain Approach in Blocking Effect Detection
G.A.Triantafyllidis, D.Tzovaras and M.G.Strintzis
International IEEE Conference on Electronics, Circuits and Systems, ICECS 2001, Malta, September 2001.

Content-Based Similarity Search of VRML Models Using Shape Descriptors
Ilias Kolonias, Dimitrios Tzovaras, Stratos Malassiotis and M.G. Strintzis
International Workshop on Content-Based Multimedia Indexing, University of Brescia, Italy, September 19-21, 2001.

Occlusion Detection in Stereopairs
G.A.Triantafyllidis, D.Tzovaras and M.G.Strintzis
International Conference on Trends in Communications, EUROCON 2001, Bratislava, Slovakia, July 2001.

Blockiness Detection in Compressed Data
G.A.Triantafyllidis, D.Tzovaras and M.G.Strintzis
IEEE International Conference on Acoustics, Speech, and Signal Processing ICASSP 2001, Salt lake City, Utah, May 2001.

Content-Based Search of VRML Models Using Shape Descriptors
I.Kolonias, D.Tzovaras, S.Malassiotis and M.G.Strintzis
Proc. Euroimage ICAV 3D 2001 Conference, Mykonos, Greece, May 2001.

DCT Coefficients adjustment for deblocking compressed images
G.A.Triantafyllidis, D.Tzovaras and M.G.Strintzis
Proc. Euroimage ICAV 3D 2001 Conference, Mykonos, Greece, May 2001.

A Compound Bayes Test for Detection of Occlusion and Visible Background and Foreground Areas in Stereo
G.A.Triantafyllidis, D.Tzovaras and M.G.Strintzis
International Workshop on Digital and Computational Video, DCV'01, February 2001.

 

Publications : 2000 conferences


Deformable Boundary Detection of Stents in Angiographic Images
I.Kompatsiaris, D.Tzovaras, V.Koutkias and M.G.Strintzis
SPIE Medical Imaging 2000, San Diego, California USA, February 2000.
MIE 2000 Conference, Hannover, August 2000.

Hierarchical Representation of Surfaces using 3D Wireframes
I.Kompatsiaris, D.Tzovaras and M.G.Strintzis
WSG'2000 international conference, Plzen, Czech Republic, February 2000.

Rate-Distortion Optimal Fast Thresholding for MPEG-2 Image Sequence Coding
K.Argyraki, D.Tzovaras, N.V.Boulgouris and M.G.Strintzis
Packet Video 2000 Int'l Workshop, Cagliari, May 2000.

A Bayesian segmentation of Stereopairs
G.A.Triantafyllidis, D.Tzovaras, M.G.Strintzis
IEEE International Conference on Multimedia and Expo. (ICME2000), New York City, August 2000.

Virtual Reality Applications in Art
D. Tzovaras
Images & Sounds of the Mediterranean, Spinalonga Festival 2000, Elounda, Crete, Greece, Sep. 26-30, 2000.