Josef Kohout

Parallel Delaunay triangulation in E2 and E3 for computers with shared memory

This paper presents several parallel algorithms for the construction of the Delaunay triangulation in E^2 and E^3-one of the fundamental problems in computer graphics. The proposed algorithms are designed for parallel systems with shared memory and several processors. Such a hardware configuration (especially the case with two-processors) became widely spread in the last few years in the computer graphics area. Some of the proposed algorithms are easy to be implemented but not very efficient, while some of them prove opposite characteristics. Some of them are usable in E^2 only, other work in E^3 as well. The algorithms themselves were already published in computer graphics where the computer graphics criteria were highlighted. This paper concentrates on parallel and systematic point of view and gives detailed information about the parallelization of a computational geometry application to parallel and distributed computation oriented community.

Parallel Delaunay triangulation in E3: make it simple

The randomized incremental insertion algorithm of Delaunay triangulation in E3 is very popular due to its simplicity and stability. This paper describes a new parallel algorithm based on this approach. The goals of the proposed parallel solution are not only to make it efficient but also to make it simple. The algorithm is intended for computer architectures with several processors and shared memory. Several versions of the proposed method were tested on workstations with up to eight processors and on datasets of up to 200000 points with favorable results.

Patient-specific fibre-based models of muscle wrapping

In many biomechanical problems, the availability of a suitable model for the wrapping of muscles when undergoing movement is essential for the estimation of forces produced on and by the body during motion. This is an important factor in the Osteoporotic Virtual Physiological Human project which is investigating the likelihood of fracture for osteoporotic patients undertaking a variety of movements. The weakening of their skeletons makes them particularly vulnerable to bone fracture caused by excessive loading being placed on the bones, even in simple everyday tasks. This paper provides an overview of a novel volumetric model that describes muscle wrapping around bones and other muscles during movement, and which includes a consideration of how the orientations of the muscle fibres change during the motion. The method can calculate the form of wrapping of a muscle of medium size and visualize the outcome within tenths of seconds on commodity hardware, while conserving muscle volume. This makes the method suitable not only for educational biomedical software, but also for clinical applications used to identify weak muscles that should be strengthened during rehabilitation or to identify bone stresses in order to estimate the risk of fractures.

Parallel Delaunay triangulation based on circum-circle criterion

This paper describes a newly proposed simple and efficient parallel algorithm for the construction of the Delaunay triangulation (DT) in E2 by randomized incremental insertion. The construction of the DT is one of the fundamental problems in computer graphics. The proposed algorithm is designed for parallel systems with shared memory and several processors. Such hardware (especially with two-processors) became available in the last few years thanks to low prices and at present, there is still a lack of parallel algorithms that are simple to implement and efficient enough to be an attractive alternative to long existing serial algorithms. The designed algorithm incorporates new method for synchronization among PEs based on the simple geometric test (i.e. if no other points lie in the circum-circle of accessed triangle, this triangle can be modified independently on others PEs). We implemented the algorithm in C++ and tested it on workstations up to four processors where we reached relatively good speed-up to our serial implementation. When only two processors were used we reached even super-linear speed-up.

On digital image representation by the delaunay triangulation

This paper deals with a transformation of raster grey-scale images into a geometric representation by the Delaunay triangulation. It discusses the influence of image filtering techniques and methods for the evaluation of significance of pixels on the conversion process. Furthermore, it proposes several novel approaches for a compression of the Delaunay triangulation and compares them with existing solutions.

3D reconstruction of TMJ after resection of the cyst and the stress-strain analyses

The aim of this article is 3D analysis of the temporomandibular joint (TMJ) patient, who underwent surgery, during which the right TMJ was resected along with the ramus of mandible and consequently the joint was reconstructed with subtotal replacement. The main goal is to give a suitable formulation of mathematical model, which describes the changes of stresses in TMJ incurred after the surgery. The TMJ is a complex, sensitive and highly mobile joint which works bilaterally so each side influences the contralateral joint and because of this the distribution of the stresses is changed in the healthy joint as well. Detailed knowledge about function these are necessary for clinical application of temporomandibular joint prosthesis and also help us estimate the lifetime of the prosthesis a possibilities of alteration in the contra lateral joint components. The geometry for the 3D models is taken from the CT scan date and its numerical solution is based on the theory of semi-coercive unilateral contact problems in linear elasticity. This article provides medical part with case report, discretion of treatment, than the methods of mathematical modeling and his possibilities are described and finally results are reported.

Practically oriented parallel Delaunay triangulation in E2 for computers with shared memory

Abstract This paper describes two simple and efficient parallel algorithms for the construction of the Delaunay triangulation (DT(S)) in E2 by randomized incremental insertion. The construction of the DT(S) is one of the fundamental problems in computer graphics. The proposed algorithms are designed for parallel systems several processors and with shared memory. Such a hardware configuration (especially the case with two-processors) became widely available in the last few years thanks to low prices at present, but there is still a lack of parallel algorithms that are simple to implement and efficient enough to be an attractive alternative to existing serial algorithms. We have implemented both new algorithms in C++ and tested them on workstations with up to four processors. Thanks to memory caching we noticed several times even super-linear speed-up compared with the reference sequential algorithm.

Real-Time Modelling of Fibrous Muscle

Relatively recently it has become apparent that providing human kind with a better healthcare requires personalized, predictive and integrative medicine, for which the building of virtual physiological human (VPH) framework accessible via virtual patient avatar is necessary. Real‐time modelling and visual exploration of such a complex avatar is a challenging task. In this paper, we propose a real‐time method for automatic modelling of an arbitrarily large number of muscle fibres in the volume of a muscle represented by its surface mesh. The method is based on an iterative morphing of predefined fibres template into the muscle volume exploiting harmonic scalar field computed on the surface of muscle. Experiments with muscles of thighs and pelvis show that the method produces realistic shapes of fibres. Our sequential VTK‐based C++ implementation is capable of producing 64 fine fibres within a muscle of 10K triangles in less than 170 ms on commodity hardware making the method suitable for VPH purposes as well as for interactive educational medical software.

On-line Blood Glucose Level Calculation

Diabetes is a silent disease. It is the 8th most common cause of death that does not hurt until it is too late and the disease has developed. Technology plays a vital role in managing diabetes and educating patients about importance of the treatment. The patient must be able to manage his blood glucose level. However, blood glucose level is measured sporadically as it causes important discomfort to the patient. Measuring glucose level in subcutaneous tissue is minimally invasive technique and thus considerably comfortable, but this level may be different from blood glucose level. We implemented a recently proposed method of blood glucose level calculation from the continuously measured subcutaneous tissue glucose level. Then, we developed a web portal that makes this method accessible to any doctors office and any diabetic patient. To the best of our knowledge, we are the very first web portal that does this. In this paper, we describe the portal.

Science on a Sphere

This paper describes applied research provided in cooperation of the Faculty of Applied Sciences and the Techmania Science Centre. It presents the unique system Science on a Sphere, its features, control mechanisms and limitations. The special visualization system brings a new approach of geographical data presentation. On the other hand it offers just a minimal opportunity of user interaction. Interaction should enable better participation of science centre in the learning process. The paper shows the ways how the existing projection system Science on a Sphere has been extended for the interactive features.