Sabry El-Hakim

• Doctor of Philosophy (PhD)
• Principal Investigator at National Research Council Canada

3D digitisation denotes the process of describing parts of our physical world through finite measurements and representations that can be processed and visuali sed with a computer system. Reality-based 3D digitisation is essential for the documentation, conservation and preservation of our Cultural Heritage. This article composes a critical review...

n this paper we developed an approach to 3D modeling of complex architecture such as medieval castles using multiple types of data. The method creates independent models from each type then assembles and integrates them to form one complete model of the site. The advantage of this technique is the flexibility it provides to handle complex and diffi...

One of the major masterpieces of international Gothic art (1350-1450) is located in the Aquila tower in Buonconsiglio castle, Trento, Italy. The main room in the tower is completely frescoed with the Cycle of the Months, a rare example of medieval painting on a nonreligious subject. The frescos depict medieval time month by month with stunning deta...

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An abstract is not available.

In this article developments and performance analysis of image matching for detailed surface reconstruction of heritage objects is discussed. Three dimensional image-based modeling of heritages is a very interesting topic with many possible applications. In this article we propose a multistage image-based modeling approach that requires only a limi...

This chapter intends to provide general knowledge of the processes and techniques required to create detailed photo-realistic shape representation from point clouds and to visually interact with it in a non-immersive or immersive environment. Image sequences or range sensors may be used to capture the 3-D data. The presented work comes from compute...

Three-dimensional documentation of heritage buildings is important for conservation, restoration and education. When it comes to complex architectural structures such as castles, no single modelling technique is capable of yielding cost-effective, highly detailed and accurate photo-realism. The authors demonstrate how integration of multiple techni...

Motivated by the need for fast, accurate, and high-resolution approach to document heritage and archaeological sites before they are removed or destroyed, the goal of this paper is to develop and demonstrate advanced image-based techniques to capture the fine 3D geometric details of such sites. The size of the site can be large and of any arbitrary...

In this contribution, we report on the image-based modeling (IBM) results of the Erechtheion monument, located inside the Acropolis of Athens, Greece. The work is part of the project "Development of Geographic Information Systems at the Acropolis of Athens". An aim of the project is the 3D documentation of the whole Acropolis, one of the major arch...

We present the procedure and technologies used to modelling of the Erechtheion at the Acropolis in Athens, a large complex structure with many challenges to data acquisition, processing, and visualisation. We used two scanners, one for medium range highresolution coverage (1-5 mm lateral data spacing) and one long-range scanner to capture some top...

Digitally documenting complex heritage sites such as castles is a desirable yet difficult task with no established framework. Although 3D digitizing and modelling with laser scanners, Photogrammetry, and computer aided architectural design (CAAD) are maturing, each alone is inadequate to model an entire castle in details.We present a sequential app...

Digitally documenting complex heritage sites such as castles is a desirable yet difficult task with no established framework. Although 3D digitizing and modelling with laser scanners, Photogrammetry, and computer aided architectural design (CAAD) are maturing, each alone is inadequate to model an entire castle in details. We present a sequential ap...

The digital documentation of monuments and architectures is an important field of application of the 3D modeling where both visual quality and precise 3D measurement are important. This paper proposes an integrated approach based upon the combination of different 3D modeling techniques for the virtual reconstruction of complex architectures like th...

According to an UNESCO survey, Italy accounts for more than half of the Cultural Heritage of the entire world. Italy's Cultural Heritage therefore represents an enormous wealth not only for the country itself but also for the entire world and this asset should be preserved and documented for future generations and possibly used as source of revenue...

This paper summarizes our initial work in evaluating 3D imaging systems at our state of the art newly constructed and equipped metrology laboratory. Completed in 2006, the laboratory space allows accurate measurements of 3D data from devices operating at standoff distances from a few centimeters up to 10 meters. A laminar flow of 20°C air at 50% hu...

Virtual time travel from existing remains of a heritage site to its previous states and original condition is an educational and interesting experience and can provide better understanding of history. However, digitally reconstructing non-existing objects is a challenge. The interaction and navigation within virtual 4D worlds (adding time to 3D wor...

In this paper the main problems and the available solutions are addressed for the generation of 3D models from terrestrial images. Close range photogrammetry has dealt for many years with manual or automatic image measurements for precise 3D modelling. Nowadays 3D scanners are also becoming a standard source for input data in many application areas...

In this paper we address the main problems and available solutions for the genera- tion of 3D models from terrestrial images. Close range photogrammetry deals since many years with manual or automatic image measurements for precise 3D modeling. Nowadays 3D scan- ners are also becoming a standard source for input data in many application areas, but...

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This paper presents the work that was accomplished in preparing multimedia products for cultural heritage interpretation and entertainment. Data fusion techniques were applied to three cases: the remains of Temple C of Selinunte, Sicily, the Byzantine Crypt of Santa Cristina, Apulia and a bronze sculpture from the 6th century BC found in Ugento, Ap...

This paper looks at the opportunities and challenges created by new 3D technologies introduced recently in the context of virtual reconstruction of cultural heritage sites for preservation and entertainment. A number of projects carried out by the authors in the last four years support the conclusions made in this paper. The projects presented incl...

We present a sequential multi-stage segment-based modelling from images procedure designed to model the fine geometric details with high-resolution meshes. Results from one stage guide the next stage. The objective is to increase the geometric details at the modelling phase in an automatic and reliable manner to achieve photo-realistic visualisatio...

The National Research Council of Canada (NRC) has developed a range of 3D imaging technology tools, which have been applied to a wide range of museum and heritage recording applications. The technology suite includes the development of high-resolution laser scanner systems as well as software for the preparation of accurate 3D models and for the di...

Digitally reconstructing a large and complex heritage site, for example a medieval castle, for documentation and virtual reality simulation is a challenging task that requires combining models created by different data sets from several digitisation technologies. Our approach resembles the level of detail (LOD) concept used in visualization of comp...

A joint project between the Interdept. Research Center of the University of Padova (CIRGEO), a research group of Istituto Tecnico per la Ricerca Scientifica e Tecnologica (IRST) of Trento and the Visual Information Technology group (VIT) of the NRC Canada, in Ottawa, has been undertaken, with the main aim to create a set of 3D models of an historic...

Many cultural heritage applications require 3D reconstruction of real-world objects and scenes. Over the past few years, it has become increasingly common to use 3D digitization and modeling for this purpose. This is mainly due to advances in laser-scanning techniques, 3D modeling software, image-based modeling techniques, computer power, and virtu...

Selecting the most effective technique for modeling large-scale heritage sites is not always obvious. This article discusses each technique and points out advantages and disadvantages. The article presents the authors' own approach, which is an integration of several technologies and is based on the experience they gained over more than a decade fo...

A technique to digitally document and thereby permanently preserve prehistoric rock art has been developed. Laser scanning and texture mapping from digital images were used. Methods involving texture mapping require the exact relationships between the image and geometrical sensors. For geological structures, such as caves, the distinctive features...

This paper presents a summary of the 3-D modelling work that was accomplished in preparing multimedia products for cultural heritage interpretation and entertainment. The two cases presented are the Byzantine Crypt of Santa Cristina, Apulia and temple C of Selinunte, Sicily. The core of the approach is based upon high-resolution photo-realistic tex...

A technique to digitally document and thereby permanently preserve prehistoric rock art has been developed. Laser scanning and texture mapping from digital images were used. Methods involving texture mapping require the exact relationships between the image and geometrical sensors. For geological structures, such as caves, the distinctive features...

The National Research Council of Canada (NRC) has collaborated with numerous Canadian and international heritage institutions on the development of a complete suite of 3D imaging technologies for archival quality imaging, analysis and display of 3D models of museum objects and heritage sites including ancient crypt and grottos. The technology inclu...

This paper presents a summary of the 3D modeling work that was accomplished in preparing multimedia products for cultural heritage interpretation and entertainment. The three cases presented are the Byzantine Crypt of Santa Cristina, Apulia, temple C of Selinunte, Sicily, and a bronze sculpture from the 6(th) century BC found in Ugento, Apulia. The...

Over the past few years, a remarkable increase has occurred in the demand for 3D models for cultural heritage applications. The techniques employed have evolved from surveying and CAD tools and/or traditional photogrammetry into laser scanning and more automated image-based techniques. However, selecting the most effective technique for a given pro...

Archaeology is emerging as one of the key areas of applications for laser range imaging. This particular context imposes a number of specific constraints on the design and operations of range sensors. In this paper, we discuss some of the issues in designing and using laser range sensor systems for archaeology. Results obtained on remote archaeolog...

The National Research Council of Canada (NRC) has developed and patented three high-resolution 3D imaging systems and processing algorithms which have been applied to a wide range of museum and heritage recording applications. The systems have been designed for different imaging applications and, in collaboration with a number of national and inter...

Automated digital photogrammetric systems are considered to be passive three-dimensional vision systems since they obtain object coordinates from only the information contained in intensity images. Active 3-D vision systems, such as laser scanners and structured light systems obtain the object coordinates from external information such as scanning...

3D modelling of heritage monuments has increased significantly due to advances in laser scanners, 3D modelling software and computers. The main approaches today are interactive and automatic photogrammetry, terrestrial laser ranging and image rendering. The authors discuss each approach, pointing out its advantages and disadvantages. They then pres...

This paper presents the work that was accomplished in preparing a multimedia CDROM about the history of a Byzantine Crypt. An effective approach based upon high-resolution photo-realistic texture mapping onto 3D models generated from range images is used to present the spatial information about the Crypt. Usually, this information is presented on 2...

We address the main issues in real-time visualization and interactive manipulation of highly textured sur- faces. For applications such as cultural heritage, achieving this will give a vista to scientists, conserva- tionists, historians, and visitors for looking at and studying important frescoed surfaces in virtual reality. Since photo-realism is...

This paper presents the 3D modelling work that was accomplished in preparing a multimedia CDROM about the history of a Byzantine Crypt. An effective approach based upon high-resolution photo-realistic texture mapping onto 3D models generated from range images is used to present the spatial information about the Crypt. Usually, this information is p...

High-resolution 3D imaging and modeling is an important application in the heritage field. We describe several demonstration projects conducted in collaboration with museums and conservation agencies

Patient respiration during radiotherapy can cause significant motion of the tumour volume, which can be mitigated by gating the accelerator beam to patient respiration. This work describes a machine-vision respiratory-gating system, based on our reported photogrammetric patient position measurement technique. La respiration du patient durant la rad...

In this paper, we compare the accuracy and resolution of a 3D-laser scanner prototype that tracks in real-time and computes the relative pose of objects in a 3D space. This 3D-laser scanner prototype was specifically developed to study the use of such a sensor for space applications. The main objective of this project is to provide a robust sensor...

Advances in the 3D sensing of dynamics and unstructured environments require the development of intelligent systems, algorithms, and methods to replace or at least minimize the human intervention to the 3D acquisition process. From the user point of view, most existing 3D acquisition systems still require static techniques that can be considered ar...

Three-dimensional modeling from images, when carried out entirely by a human, can be time consuming and impractical for large-scale projects. On the other hand, full automation may be unachievable or not accurate enough for many applications such as culture heritage documentation. In addition, three-dimensional modeling from images, particularly fu...

Three-dimensional modeling from images, when carried out entirely by a human, is time consuming and impractical for large-scale projects. On the other hand, full automation may still be unachievable for many applications. In addition, 3D modeling from images requires the extraction of features and needs them to appear in multiple images. However, i...

In recent years, high-resolution recording of heritage sites has stimulated a lot of research in fields like photogrammetry, computer vision, and computer graphics. Numerous algorithms and methodologies have been proposed in the literature for heritage recording from photogrammetry and laser scanner 3D data. In practice, what a 3D photographer need...

In recent years, high-resolution recording of heritage sites has stimulated a lot of research in fields like photogrammetry, computer vision, and computer graphics. Numerous algorithms and methodologies have been proposed in the literature. In practice, what a 3D photographer needs is a commercially available solution to this so-called as-built doc...

Geometrical tracking and pose estimation using the homogeneous UVW inverse spherical coordinate system, directly from range data obtained from a triangulation based range sensor, are demonstrated. The method is shown to be more accurate, reliable, and computationally faster than using the more conventional XYZ Cartesian coordinate system. This is p...

possible to obtain such images, for example when reconstructing destroyed structures using existing photographs or paintings with proper perspective (figure 1), and reconstructing objects without actually visiting the site using images from the web or postcards (figure 2). Even when multiple images are possible, parts of the scene appear in only on...

An intuitive technique for managing three-dimensional objects by shape is presented. This technique is applied to the Virtual Museum in the framework of heritage applications. The Virtual Museum is a virtual reality-based museum that allows the public to visualise, compare, manipulate and search the collection with an intuitive query by shape parad...

Creating geometrically correct and complete 3D models of complex environments remains a difficult problem. Techniques for 3D digitizing and modeling have been rapidly advancing over the past few years although most focus on single objects or specific applications such as architecture and city mapping. The ability to capture details and the degree o...

The Virtual Boutique is made out of three modules: the decor, the market and the search engine. The decor is the physical space occupied by the Virtual Boutique. It can reproduce any existing boutique. For this purpose, photogrammetry is used. A set of pictures of a real boutique or space is taken and a virtual D representation of this space is cal...

Creating geometrically correct and complete 3D models of complex environments remains a difficult problem. Techniques for 3D digitizing and modeling have been rapidly advancing over the past few years although most focus on single objects or specific applications such as architecture and city mapping. The ability to capture details and the degree o...

In this paper, we compare the accuracy and resolution of a 3D-laser scanner prototype that tracks in real-time and computes the relative pose of objects in a 3D space. This 3D-laser scanner prototype was specifically developed to study the use of such a sensor for space applications. The main objective of this project is to provide a robust sensor...

This paper summarises the results achieved from a number of laser scanning experiments performed in our laboratories and on remote sites. The potential of this technology for imaging applications and as an input to virtualised reality environments is discussed. Parameters to be considered for this type of activity are related to the design of laser...

Creating virtual environment models often requires geometric data from range sensors as well as photometric data from CCD cameras. The model must be geometrically correct, visually realistic, and small enough in size to allow real-time rendering. We present an approach based on 3D range sensor data, multiple CCD cameras, and a colour high-resolutio...

This paper describes a generic technology for modeling in real time the various operations of surface mines. Based on various sensor fusion techniques and high-speed network, a virtual reality model of a mine capable of representing not only static infrastructures but also mobile equipment such as trucks and excavators is created. The modeling tech...

This paper describes a general system for creating geometrically correct and complete 3D models of objects and environments. The main process uses digital images and applies rigorous photogrammetric techniques. Once the images are registered using bundle adjustment, points in selected locations are measured in all the images where they appear. Howe...

A compact digital 3D imaging system based on laser triangulation was designed for applications requiring a rapid response on remote sites. Heritage, forensic and industrial applications are among the best fields to benefit from this new technology. This paper focuses on such aspects as the acquisition, calibration, verification, and model creation....

Selecting the appropriate 3-D capture and modeling technologies to create the contents of a virtual environment (VE) remains a challenging task. One of the objectives of the environment-modeling project in our laboratory is to develop a design strategy for selecting the optimum sensor technology and its configuration to meet the requirements for vi...

Creating virtual environment models often requires geometric data from range sensors as well as photometric data from CCD cameras. The model must be geometrically correct, visually realistic, and small enough in size to allow real-time rendering. We present an approach based on 3D range sensor data, multiple CCD cameras, and a colour high-resolutio...

Creating virtual environment models often requires geometric data from range sensors as well as photometric data from CCD cameras. The model must be geometrically correct, visually realistic, and small enough in size to allow real-time rendering. We present an approach based on 3D range sensor data, multiple CCD cameras, and a high-resolution digit...

A system that can rapidly, reliably, remotely and accurately create a photo-realistic 3D model of indoor environments is needed for many applications. In this paper, we present a mobile mapping system that is designed to generate such models automatically from various sensors. Surfaces and features can be accurately mapped from images acquired by a...

The key to navigate in a D environment or designing autonomous vehicles that can successfully maneuver and manipulate objects in their environment is the ability to create, maintain, and use effectively a 3D digital model that accurately represents its physical counterpart. Virtual exploring of real places and environments, either for leisure, engi...

Due to the nature of many applications, it is difficult with present technology to use a single type of sensor to automatically, accurately, reliably, and completely measure or map, in three-dimensions, objects, sites, or scenes. Therefore, a combination of various sensor technologies is usually the obvious solution. There are several 3-D technolog...

Virtual environments (VEs) also known as virtual reality (VR) are increasingly being considered for industrial, medical, and educational / training applications, to name a few. A VE provides real-time interaction with 3-D models when combined with a display technology that gives the user immersion in the model world and direct manipulation of objec...

Active 3-D vision systems, such as laser scanners and structured light systems, obtain the object coordinates from external information such as scanning angles, time of flight, or shape of projected patterns. Passive systems require well-defined features such as targets and edges and are affected by ambient light. Therefore, they have difficulty wi...

This paper demonstrates the accuracy of a prototype Laser Range Camera (LRC) developed at the National Research Council of Canada for the creation of models of real objects. A laser survey performed in collaboration with the Canadian Space Agency and NASA is used as a test case. The object selected for this particular test case is the Orbiter Docki...

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Conventional vision techniques based on intensity data, such as the data produced by CCD cameras, cannot produce complete 3D measurements for object surfaces. Range sensors, such as laser scanners, do provide complete range data for visible surfaces; however, they may produce erroneous results on surface discontinuities such as edges. In most appli...

We have developed and clinically tested a computer vision system capable of real time monitoring of the position of an oncology (cancer) patient undergoing radiation therapy. The system is able to report variations in patient setup from day to day, as well as patient motion during an individual treatment. The system consists of two CCD cameras moun...

We have developed and clinically tested a computer vision system capable of real time monitoring of the position of an oncology (cancer) patient undergoing radiation therapy. The system is able to report variations in patient setup from day to day, as well as patient motion during an individual treatment. The system consists of two CCD cameras moun...

Conventional vision techniques based on intensity data, such as the data produced by CCD cameras, cannot produce complete 3D measurements for object surfaces. Range sensors, such as laser scanners, do provide complete range data for visible surfaces; however, they may produce erroneous results on surface discontinuities such as edges. In most appli...

This paper presents a calibration procedure adapted to a range camera intended for space applications. The range camera, which is based upon an auto-synchronized triangulation scheme, can measure objects from about 0.5 m to 100 m. The field of view is 30 degree(s) X 30 degree(s). Objects situated at distances beyond 10 m can be measured with the he...

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Applications such as dimensional inspection, positioning and tracking of objects, and reverse engineering require highly accurate measurement systems. A vision-based coordinate measurement system (VCM) developed at the National Research Council of Canada, targeted for these applications, will be described. In order for a vision system to be conside...

Applications such as dimensional inspection, positioning and tracking of objects, and reverse engineering require highly accurate measurement systems. A vision-based coordinate measurement system (VCM) developed at the National Research Council of Canada, targeted for these applications, will be described. In order for a vision system to be conside...

Topics addressed include camera and system calibration; surface/object reconstruction; precision measurement techniques for computer vision; and industrial applications of vision metrology systems. Particular attention is given to stereo camera system calibration with relative orientation constraints, camera calibration used on coplanar points, obj...

Detecting edges using generic edge detection techniques is often unsuccessful in detecting all the edges of interest under practical lighting conditions. Even if the edges are detected successfully, the problem of determining the 3-d coordinates remains difficult without apriori knowledge of the objecL A procedure for edge extraction under less tha...

The vision-based coordinate measurement (VCM) automated measurement system has been under development at the National Research Council Canada for several years. The system, which is a multicamera passive system, combines the principles of stereo vision, photogrammetry, knowledge-based techniques, and object-oriented design to provide precise coordi...