Zeljka Mihajlovic - Academia.edu (original) (raw)

Papers by Zeljka Mihajlovic

2014 37th International Convention on Information and Communication Technology, Electronics and Microelectronics (MIPRO), 2014

ABSTRACT This paper is focused on the methods used to visualize meteorological factors based on t... more ABSTRACT This paper is focused on the methods used to visualize meteorological factors based on the given data. Properties of the factors for which the data can be gathered were described and the methods of visualizing those properties have been examined. The program solution is centered around interaction with the weather data. The data itself is based on real measurements. It is possible to select an exact point in time for which the data exists, and that data is then visualized on a 3D model of a building, which allows the user to get an idea of the weather state. The model changes lighting, shadows, clouds, opacity and the rotation of a wind vane, based on the data. The data is also represented by graphs, which allow the user to track data changes over a period of time. Finally, since the solution uses large amount of data, a performance analysis was done to point out advantages and disadvantages of the visualization methods used.

In this paper we briefly outline theoretical fundamentals of fluid dynamics as well as present a ... more In this paper we briefly outline theoretical fundamentals of fluid dynamics as well as present a model for computer based simulation. Of special interest are target driven smoke simulations which don't require expert knowledge in order to achieve desired results. One of such methods was presented and implemented in two dimensions using programming language C++. The results obtained are presented alongside parameters that affect the progress of simulation.

Abstract— The quality of computer rendering and perception of realism greatly depend on the shadi... more Abstract— The quality of computer rendering and perception of realism greatly depend on the shading method used to implement the interaction of light with the surfaces of objects in a scene. Ambient occlusion (AO) enhances the realistic impression of rendered objects and scenes. Properties that make Screen Space Ambient Occlusion (SSAO) interesting for real-time graphics are scene complexity independence, and support for fully dynamic scenes. However, there are also important issues with current approaches: poor texture cache use, introduction of noise, and performance swings. In this paper, a straightforward solution is presented. Instead of a traditional, geometry-based sampling method, a novel, image-based sampling method is developed, coupled with a revised heuristic function for computing occlusion. Proposed algorithm harnessing GPU power improves texture cache use and reduces aliasing artifacts. Two implementations are developed, traditional and novel, and their comparison rev...

American Journal of Otolaryngology, 2002

Foreign bodies in paranasal sinuses are found quite infrequently. They are usually detected after... more Foreign bodies in paranasal sinuses are found quite infrequently. They are usually detected after various types of head trauma and most commonly occur as a consequence of improper handling of firearms or explosives. In countries at war, eg, during the war in Croatia, adults and children were almost equally exposed to these injuries. The diagnosis should be based on results from precise computer tomography (CT) scanning in axial and coronal sections, and, using these data, tissues of different densities at these anatomical locations can be differentiated. The possibility of exact preoperative, noninvasive visualization of the spatial relationships of anatomic and pathologic structures with 3-dimensional (3D) computerassisted diagnosis and intraoperative navigational techniques allows the surgeon to achieve a considerable advantage in the preoperative examination of the patient and to reduce the risk of intraoperative complications, all by the use of virtual surgery (VS) or virtual diagnosis. The expected contribution of the mentioned computer-assisted surgical technique manifests itself in defining the most appropriate mode of CT scanning of the head to design the 3D operating field model, and the possibility of active and dynamic 3D visualization of the desired anatomical regions is realized. 3D reconstruction of anatomic units becomes a routine preoperative procedure, providing a highly useful and informative visualization of the regions of interest, and, thus, advancing the definition of geometric information on anatomical contours of the 3D model by the transfer of so-called image pixel to contour pixel.

2016 39th International Convention on Information and Communication Technology, Electronics and Microelectronics (MIPRO), 2016

International Journal of Engineering Education, 2010

We present the design, technical issues and use of a software environment for learning and educat... more We present the design, technical issues and use of a software environment for learning and educational assessment. Our proposed system offers individualized tasks for each student and allows variations and modifications of the tasks (with instructor supervision). The system is designed to support distance learning, but it can also support and enrich education in a traditional classroom. Using application-based computer graphics tasks, we present various potential uses of the proposed software environment. Computer graphics tasks are highly demanding for interactivity, visual presentation and simulation. The proposed design addresses the most demanding graphics challenges. We demonstrate that the proposed framework applies to different courses and that this mode of learning is highly motivating for students.

Proceedings of the 11th Acm Siggraph International Conference on Virtual Reality Continuum and Its Applications in Industry, Dec 2, 2012

This paper describes a system for object detection and tracking implemented as an iPad applicatio... more This paper describes a system for object detection and tracking implemented as an iPad application, which has been tested and successfully accomplishes its task. The system is based on finding the initial position of the object by matching features between a template and the device's picture. Tracking is achieved by using a pyramidal implementation of the iterative Lucas-Kanade algorithm.

Proceedings of the 2004 11th IEEE International Conference on Electronics, Circuits and Systems, 2004. ICECS 2004., 2004

We present real-time shadow method based on the shadow volume that exploit capabilities of the mo... more We present real-time shadow method based on the shadow volume that exploit capabilities of the modern graphics cards. Algorithm is primarily created for casting shadows of a highly concave complex objects such as trees. For those objects silhouette calculation that is usually preformed by other shadow volume algorithms is complicated and poorly justified. Instead of calculations, it is better to assume a worst case scenario and use all of the edges for construction of the shadow volume mesh, skipping silhouette determination entirely. The achieved benefit is that all procedure, the object and shadow calculation and rendering, could be done on GPU. Proposed solution for shadow casting allows open edges. Indexed vertex blending is used for shadow projections, and the only calculation required is determining projection matrices. Once created, shadow volume is treated like any other mesh.

2015 38th International Convention on Information and Communication Technology, Electronics and Microelectronics (MIPRO), 2015

Terrain models typically contain huge amount of data so they are very time consuming for visualiz... more Terrain models typically contain huge amount of data so they are very time consuming for visualization purposes. This especially comes to the forefront when urban environments are included. The main compromise in representation of the complex environments is between achieved quality and time consumption. With the simple texture representation of complex environments we will accomplish fast application, and with the large polygonal meshes, high quality of the rendered scene. In this paper we propose rendering of urban and natural environments using parallax and relief mapping. This approach combines benefits of the rendering of polygonal meshes and texture approach. Thereby, in the proposed approach improved quality on the one side and increased speed on the other side is combined. The applicability of the method is demonstrated trough parallax and relief mapping within the Irrilicht open source graphics engine. The shaders programs were made with the GLSL shader language. As the res...

International Journal of Engineering Education

In this paper we present a successful implementation of a new software environment for learning a... more In this paper we present a successful implementation of a new software environment for learning and knowledge assessment. We introduce a new kind of gadget that is appropriate for inclusion in learning environments. The proposed gadgets are based on individualized interactive graphics tasks that are similar to educational Java applets. However, the usual graphical applets are not individualized: they do not have a defined goal for the learner and they do not evaluate the solution to a given graphical task. Using several examples, we present the development of the gadgets. The development of gadgets must address two problems: how to create and present an individualized task to the student and how to evaluate the student's solution, especially when multiple solutions are possible or solutions can be partially correct. The tasks that are described in this paper are intended for learning and knowledge assessment in computer graphics courses. However, the proposed concept is applicab...

Paper explores methods of achieving natural interaction between the virtual and the real world, a... more Paper explores methods of achieving natural interaction between the virtual and the real world, along with their application in industry. Significant emphasis is given to the Microsoft Kinect device, whose functionality was introduced in the field of powertrain systems industry. Collaboration with Austrian company AVL, which is engaged in development, testing and simulation of powertrain systems, has contributed with specific problem that can be solved in augmented reality domain. In order to facilitate maintenance of special device for continuous measurement of lowest soot concentration in the diluted exhaust from internal combustion engines, an interactive virtual service manual has been developed. The application uses interaction with the Microsoft Kinect device which enables users to control and interact with computer world through a natural user interface using gestures and spoken commands. The device finds greatest application in interactive entertainment, but this paper prese...

MELECON 2008 - The 14th IEEE Mediterranean Electrotechnical Conference, 2008

This paper presents a GPS based system for naval navigation and the development process of such s... more This paper presents a GPS based system for naval navigation and the development process of such system. In this paper path finding algorithm for naval navigation is proposed that is appropriate for implementation on Pocket PC device. The implementation of the proposed system requires some specific adapting of a number of other algorithms and methods to run well on embedded systems like Pocket PC device. Experimental results are presented using developed configuration. Adriatic coast is used as surroundings, because it is highly indented, so it presents one of the most demanding challenges. 1

Proceedings of the 12th IEEE Mediterranean Electrotechnical Conference (IEEE Cat. No.04CH37521), 2004

Paper describes research done on algorithms for the generation of gouge-free nonisoparametric too... more Paper describes research done on algorithms for the generation of gouge-free nonisoparametric tool paths across surface plane segments obtained through triangulation partitioning. Along with contiguous trajectory sequences, adaptive tool path planning introduces partially discontinuous tool trajectories. Algorithm achieves the necessary trajectory continuity by the insertion of the auxiliary tool-orientation trajectories. The tool passes over the path gaps are accomplished through rapid tool traverses. The evaluation of surface machining optimization is provided by simulation of computed tool motion trajectories applied to triangulation models. Tool tracks and tool trajectories obtained with different surface models are used for presentation and examination of the optimized tool path modeling and algorithm computing performance issues.

Proceedings of the 12th IEEE Mediterranean Electrotechnical Conference (IEEE Cat. No.04CH37521), 2004

This paper deals with surface reconstruction and the gradient reconstruction in the volume render... more This paper deals with surface reconstruction and the gradient reconstruction in the volume rendering. In the volume rendering procedure, reconstruction according to the discrete set of samples is required. Due to the reconstruction procedure alias artifacts, in the final image, could not be neglected. In this paper we focus our attention on the gradient reconstruction based on the surface reconstruction. For the surface reconstruction we use the cubic B-splines and for the gradient reconstruction corresponding derivative.

ISIE '99. Proceedings of the IEEE International Symposium on Industrial Electronics (Cat. No.99TH8465), 1999

This paper describes B-spline interpolation and compares it with other reconstruction methods, es... more This paper describes B-spline interpolation and compares it with other reconstruction methods, especially in three-dimensional space. We rst consider the B-spline bases in the terms of convolution in signal processing. Presented analysis requires careful usage of continuous and discrete representation of B-splines. Emphasis is given to important di erence between B-spline interpolation and approximation. The di erence is shown through frequency domain analysis, so we derive frequency responses of the Bspline interpolation and approximation. We conclude by demonstrating the use of several reconstruction lters and appropriate gradient estimators in the volume rendering. Exact reconstruction in the volume visualization is very important in many industrial applications, such as material cavity control.

2014 37th International Convention on Information and Communication Technology, Electronics and Microelectronics (MIPRO), 2014

ABSTRACT Automated grading of multiple-choice exams is of great interest in university courses wi... more ABSTRACT Automated grading of multiple-choice exams is of great interest in university courses with a large number of students. We consider an existing system in which exams are automatically graded using simple answer sheets that are annotated by the student. A sheet consists of a series of circles representing possible answers. As annotation errors are possible, a student is permitted to alter the annotated answer by annotating the“error” circle and handwriting the letter of the correct answer next to the appropriate row. During the scanning process, if an annotated“error” circle is detected, the system raises an alarm and requires intervention from a human operator to determine which answer to consider valid. We propose rather simple and effecive computer vision algorithm which enables automated reading of a limited set of handwritten answers and minimizes the need for a human intervention in the scanning process. We test our algorithm on a large dataset of real scanned answer sheets, and report encouraging performance rates.

Proceedings of the 11th ACM SIGGRAPH International Conference on Virtual-Reality Continuum and its Applications in Industry - VRCAI '12, 2012

This paper describes a system for object detection and tracking implemented as an iPad applicatio... more This paper describes a system for object detection and tracking implemented as an iPad application, which has been tested and successfully accomplishes its task. The system is based on finding the initial position of the object by matching features between a template and the device's picture. Tracking is achieved by using a pyramidal implementation of the iterative Lucas-Kanade algorithm.

9th International Conference on Electronics, Circuits and Systems, 2002

IEEE International Conference on Industrial Technology, 2003, 2003

This paper deals with reconstruction of the gradient in the volume element space that is required... more This paper deals with reconstruction of the gradient in the volume element space that is required for shading in the volume rendering. The accuracy of the surface reconstruction in the volume rendering is very important task as well as reconstruction accuracy of the normal vector. The central difference operator is often used as approximation of the gradient. The gradient reconstruction is an essential operation for determination of illumination and it has a great impact on the appearance of the reconstructed surface of an object. Our reconstruction of the gradient is based on the cubic approximation or interpolation B-splines. Volume rendering is visualization technique with widespread applicability in many fields, from the medical visualization to the engine visualization. Artefacts introduced by the surface reconstruction or the gradient reconstruction are of the crucial importance for perception of the projected object. KEY WORDS -gradient, reconstruction, B-splines, volume rendering 0-7803-7852-0/03/$17.00

2014 37th International Convention on Information and Communication Technology, Electronics and Microelectronics (MIPRO), 2014

ABSTRACT This paper is focused on the methods used to visualize meteorological factors based on t... more ABSTRACT This paper is focused on the methods used to visualize meteorological factors based on the given data. Properties of the factors for which the data can be gathered were described and the methods of visualizing those properties have been examined. The program solution is centered around interaction with the weather data. The data itself is based on real measurements. It is possible to select an exact point in time for which the data exists, and that data is then visualized on a 3D model of a building, which allows the user to get an idea of the weather state. The model changes lighting, shadows, clouds, opacity and the rotation of a wind vane, based on the data. The data is also represented by graphs, which allow the user to track data changes over a period of time. Finally, since the solution uses large amount of data, a performance analysis was done to point out advantages and disadvantages of the visualization methods used.

In this paper we briefly outline theoretical fundamentals of fluid dynamics as well as present a ... more In this paper we briefly outline theoretical fundamentals of fluid dynamics as well as present a model for computer based simulation. Of special interest are target driven smoke simulations which don't require expert knowledge in order to achieve desired results. One of such methods was presented and implemented in two dimensions using programming language C++. The results obtained are presented alongside parameters that affect the progress of simulation.

Abstract— The quality of computer rendering and perception of realism greatly depend on the shadi... more Abstract— The quality of computer rendering and perception of realism greatly depend on the shading method used to implement the interaction of light with the surfaces of objects in a scene. Ambient occlusion (AO) enhances the realistic impression of rendered objects and scenes. Properties that make Screen Space Ambient Occlusion (SSAO) interesting for real-time graphics are scene complexity independence, and support for fully dynamic scenes. However, there are also important issues with current approaches: poor texture cache use, introduction of noise, and performance swings. In this paper, a straightforward solution is presented. Instead of a traditional, geometry-based sampling method, a novel, image-based sampling method is developed, coupled with a revised heuristic function for computing occlusion. Proposed algorithm harnessing GPU power improves texture cache use and reduces aliasing artifacts. Two implementations are developed, traditional and novel, and their comparison rev...

American Journal of Otolaryngology, 2002

Foreign bodies in paranasal sinuses are found quite infrequently. They are usually detected after... more Foreign bodies in paranasal sinuses are found quite infrequently. They are usually detected after various types of head trauma and most commonly occur as a consequence of improper handling of firearms or explosives. In countries at war, eg, during the war in Croatia, adults and children were almost equally exposed to these injuries. The diagnosis should be based on results from precise computer tomography (CT) scanning in axial and coronal sections, and, using these data, tissues of different densities at these anatomical locations can be differentiated. The possibility of exact preoperative, noninvasive visualization of the spatial relationships of anatomic and pathologic structures with 3-dimensional (3D) computerassisted diagnosis and intraoperative navigational techniques allows the surgeon to achieve a considerable advantage in the preoperative examination of the patient and to reduce the risk of intraoperative complications, all by the use of virtual surgery (VS) or virtual diagnosis. The expected contribution of the mentioned computer-assisted surgical technique manifests itself in defining the most appropriate mode of CT scanning of the head to design the 3D operating field model, and the possibility of active and dynamic 3D visualization of the desired anatomical regions is realized. 3D reconstruction of anatomic units becomes a routine preoperative procedure, providing a highly useful and informative visualization of the regions of interest, and, thus, advancing the definition of geometric information on anatomical contours of the 3D model by the transfer of so-called image pixel to contour pixel.

2016 39th International Convention on Information and Communication Technology, Electronics and Microelectronics (MIPRO), 2016

International Journal of Engineering Education, 2010

We present the design, technical issues and use of a software environment for learning and educat... more We present the design, technical issues and use of a software environment for learning and educational assessment. Our proposed system offers individualized tasks for each student and allows variations and modifications of the tasks (with instructor supervision). The system is designed to support distance learning, but it can also support and enrich education in a traditional classroom. Using application-based computer graphics tasks, we present various potential uses of the proposed software environment. Computer graphics tasks are highly demanding for interactivity, visual presentation and simulation. The proposed design addresses the most demanding graphics challenges. We demonstrate that the proposed framework applies to different courses and that this mode of learning is highly motivating for students.

Proceedings of the 11th Acm Siggraph International Conference on Virtual Reality Continuum and Its Applications in Industry, Dec 2, 2012

This paper describes a system for object detection and tracking implemented as an iPad applicatio... more This paper describes a system for object detection and tracking implemented as an iPad application, which has been tested and successfully accomplishes its task. The system is based on finding the initial position of the object by matching features between a template and the device's picture. Tracking is achieved by using a pyramidal implementation of the iterative Lucas-Kanade algorithm.

Proceedings of the 2004 11th IEEE International Conference on Electronics, Circuits and Systems, 2004. ICECS 2004., 2004

We present real-time shadow method based on the shadow volume that exploit capabilities of the mo... more We present real-time shadow method based on the shadow volume that exploit capabilities of the modern graphics cards. Algorithm is primarily created for casting shadows of a highly concave complex objects such as trees. For those objects silhouette calculation that is usually preformed by other shadow volume algorithms is complicated and poorly justified. Instead of calculations, it is better to assume a worst case scenario and use all of the edges for construction of the shadow volume mesh, skipping silhouette determination entirely. The achieved benefit is that all procedure, the object and shadow calculation and rendering, could be done on GPU. Proposed solution for shadow casting allows open edges. Indexed vertex blending is used for shadow projections, and the only calculation required is determining projection matrices. Once created, shadow volume is treated like any other mesh.

2015 38th International Convention on Information and Communication Technology, Electronics and Microelectronics (MIPRO), 2015

Terrain models typically contain huge amount of data so they are very time consuming for visualiz... more Terrain models typically contain huge amount of data so they are very time consuming for visualization purposes. This especially comes to the forefront when urban environments are included. The main compromise in representation of the complex environments is between achieved quality and time consumption. With the simple texture representation of complex environments we will accomplish fast application, and with the large polygonal meshes, high quality of the rendered scene. In this paper we propose rendering of urban and natural environments using parallax and relief mapping. This approach combines benefits of the rendering of polygonal meshes and texture approach. Thereby, in the proposed approach improved quality on the one side and increased speed on the other side is combined. The applicability of the method is demonstrated trough parallax and relief mapping within the Irrilicht open source graphics engine. The shaders programs were made with the GLSL shader language. As the res...

International Journal of Engineering Education

In this paper we present a successful implementation of a new software environment for learning a... more In this paper we present a successful implementation of a new software environment for learning and knowledge assessment. We introduce a new kind of gadget that is appropriate for inclusion in learning environments. The proposed gadgets are based on individualized interactive graphics tasks that are similar to educational Java applets. However, the usual graphical applets are not individualized: they do not have a defined goal for the learner and they do not evaluate the solution to a given graphical task. Using several examples, we present the development of the gadgets. The development of gadgets must address two problems: how to create and present an individualized task to the student and how to evaluate the student's solution, especially when multiple solutions are possible or solutions can be partially correct. The tasks that are described in this paper are intended for learning and knowledge assessment in computer graphics courses. However, the proposed concept is applicab...

Paper explores methods of achieving natural interaction between the virtual and the real world, a... more Paper explores methods of achieving natural interaction between the virtual and the real world, along with their application in industry. Significant emphasis is given to the Microsoft Kinect device, whose functionality was introduced in the field of powertrain systems industry. Collaboration with Austrian company AVL, which is engaged in development, testing and simulation of powertrain systems, has contributed with specific problem that can be solved in augmented reality domain. In order to facilitate maintenance of special device for continuous measurement of lowest soot concentration in the diluted exhaust from internal combustion engines, an interactive virtual service manual has been developed. The application uses interaction with the Microsoft Kinect device which enables users to control and interact with computer world through a natural user interface using gestures and spoken commands. The device finds greatest application in interactive entertainment, but this paper prese...

MELECON 2008 - The 14th IEEE Mediterranean Electrotechnical Conference, 2008

This paper presents a GPS based system for naval navigation and the development process of such s... more This paper presents a GPS based system for naval navigation and the development process of such system. In this paper path finding algorithm for naval navigation is proposed that is appropriate for implementation on Pocket PC device. The implementation of the proposed system requires some specific adapting of a number of other algorithms and methods to run well on embedded systems like Pocket PC device. Experimental results are presented using developed configuration. Adriatic coast is used as surroundings, because it is highly indented, so it presents one of the most demanding challenges. 1

Proceedings of the 12th IEEE Mediterranean Electrotechnical Conference (IEEE Cat. No.04CH37521), 2004

Paper describes research done on algorithms for the generation of gouge-free nonisoparametric too... more Paper describes research done on algorithms for the generation of gouge-free nonisoparametric tool paths across surface plane segments obtained through triangulation partitioning. Along with contiguous trajectory sequences, adaptive tool path planning introduces partially discontinuous tool trajectories. Algorithm achieves the necessary trajectory continuity by the insertion of the auxiliary tool-orientation trajectories. The tool passes over the path gaps are accomplished through rapid tool traverses. The evaluation of surface machining optimization is provided by simulation of computed tool motion trajectories applied to triangulation models. Tool tracks and tool trajectories obtained with different surface models are used for presentation and examination of the optimized tool path modeling and algorithm computing performance issues.

Proceedings of the 12th IEEE Mediterranean Electrotechnical Conference (IEEE Cat. No.04CH37521), 2004

This paper deals with surface reconstruction and the gradient reconstruction in the volume render... more This paper deals with surface reconstruction and the gradient reconstruction in the volume rendering. In the volume rendering procedure, reconstruction according to the discrete set of samples is required. Due to the reconstruction procedure alias artifacts, in the final image, could not be neglected. In this paper we focus our attention on the gradient reconstruction based on the surface reconstruction. For the surface reconstruction we use the cubic B-splines and for the gradient reconstruction corresponding derivative.

ISIE '99. Proceedings of the IEEE International Symposium on Industrial Electronics (Cat. No.99TH8465), 1999

This paper describes B-spline interpolation and compares it with other reconstruction methods, es... more This paper describes B-spline interpolation and compares it with other reconstruction methods, especially in three-dimensional space. We rst consider the B-spline bases in the terms of convolution in signal processing. Presented analysis requires careful usage of continuous and discrete representation of B-splines. Emphasis is given to important di erence between B-spline interpolation and approximation. The di erence is shown through frequency domain analysis, so we derive frequency responses of the Bspline interpolation and approximation. We conclude by demonstrating the use of several reconstruction lters and appropriate gradient estimators in the volume rendering. Exact reconstruction in the volume visualization is very important in many industrial applications, such as material cavity control.

2014 37th International Convention on Information and Communication Technology, Electronics and Microelectronics (MIPRO), 2014

ABSTRACT Automated grading of multiple-choice exams is of great interest in university courses wi... more ABSTRACT Automated grading of multiple-choice exams is of great interest in university courses with a large number of students. We consider an existing system in which exams are automatically graded using simple answer sheets that are annotated by the student. A sheet consists of a series of circles representing possible answers. As annotation errors are possible, a student is permitted to alter the annotated answer by annotating the“error” circle and handwriting the letter of the correct answer next to the appropriate row. During the scanning process, if an annotated“error” circle is detected, the system raises an alarm and requires intervention from a human operator to determine which answer to consider valid. We propose rather simple and effecive computer vision algorithm which enables automated reading of a limited set of handwritten answers and minimizes the need for a human intervention in the scanning process. We test our algorithm on a large dataset of real scanned answer sheets, and report encouraging performance rates.

Proceedings of the 11th ACM SIGGRAPH International Conference on Virtual-Reality Continuum and its Applications in Industry - VRCAI '12, 2012

This paper describes a system for object detection and tracking implemented as an iPad applicatio... more This paper describes a system for object detection and tracking implemented as an iPad application, which has been tested and successfully accomplishes its task. The system is based on finding the initial position of the object by matching features between a template and the device's picture. Tracking is achieved by using a pyramidal implementation of the iterative Lucas-Kanade algorithm.

9th International Conference on Electronics, Circuits and Systems, 2002

IEEE International Conference on Industrial Technology, 2003, 2003

This paper deals with reconstruction of the gradient in the volume element space that is required... more This paper deals with reconstruction of the gradient in the volume element space that is required for shading in the volume rendering. The accuracy of the surface reconstruction in the volume rendering is very important task as well as reconstruction accuracy of the normal vector. The central difference operator is often used as approximation of the gradient. The gradient reconstruction is an essential operation for determination of illumination and it has a great impact on the appearance of the reconstructed surface of an object. Our reconstruction of the gradient is based on the cubic approximation or interpolation B-splines. Volume rendering is visualization technique with widespread applicability in many fields, from the medical visualization to the engine visualization. Artefacts introduced by the surface reconstruction or the gradient reconstruction are of the crucial importance for perception of the projected object. KEY WORDS -gradient, reconstruction, B-splines, volume rendering 0-7803-7852-0/03/$17.00