Implementing intersection calculations of the ray tracing algorithm with systolic arrays

Ray tracing is one technique that has been used to synthesize realistic images with a computer. Unfortunately, this technique, when implemented in software, is slow and expensive. The trend in computer graphics has been toward the use of special purpose hardware, to speed up the calculations, and, hence, the generation of the synthesized image. This paper describes the design and the operation of a systolic based architecture, tailored to speed up the intersection calculations, that must be performed as a part of the ray tracing algorithm

Hybrid modelling of time-variant heterogeneous objects.

The physical world consists of a wide range of objects of a diverse constitution. Past research was mainly focussed on the modelling of simple homogeneous objects of a uniform constitution. Such research resulted in the development of a number of advanced theoretical concepts and practical techniques for describing such physical objects. As a result, the process of modelling and animating certain types of homogeneous objects became feasible. In fact most physical objects are not homogeneous but heterogeneous in their constitution and it is thus important that one is able to deal with such heterogeneous objects that are composed of diverse materials and may have complex internal structures. Heterogeneous object modelling is still a very new and evolving research area, which is likely to prove useful in a wide range of application areas. Despite its great promise, heterogeneous object modelling is still at an embryonic state of development and there is a dearth of extant tools that would allow one to work with static and dynamic heterogeneous objects. In addition, the heterogeneous nature of the modelled objects makes it appealing to employ a combination of different representations resulting in the creation of hybrid models. In this thesis we present a new dynamic Implicit Complexes (IC) framework incorporating a number of existing representations and animation techniques. This framework can be used for the modelling of dynamic multidimensional heterogeneous objects. We then introduce an Implicit Complexes Application Programming Interface (IC API). This IC API is designed to provide various applications with a unified set of tools allowing these to model time-variant heterogeneous objects. We also present a new Function Representation (FRep) API, which is used for the integration of FReps into complex time-variant hybrid models. This approach allows us to create a practical multilevel modelling system suited for complex multidimensional hybrid modelling of dynamic heterogeneous objects. We demonstrate the advantages of our approach through the introduction of a novel set of tools tailored to problems encountered in simulation applications, computer animation and computer games. These new tools empower users and amplify their creativity by allowing them to overcome a large number of extant modelling and animation problems, which were previously considered difficult or even impossible to solve

Workshop on the Integration of Finite Element Modeling with Geometric Modeling

The workshop on the Integration of Finite Element Modeling with Geometric Modeling was held on 12 May 1987. It was held to discuss the geometric modeling requirements of the finite element modeling process and to better understand the technical aspects of the integration of these two areas. The 11 papers are presented except for one for which only the abstract is given

Research reports: 1985 NASA/ASEE Summer Faculty Fellowship Program

A compilation of 40 technical reports on research conducted by participants in the 1985 NASA/ASEE Summer Faculty Fellowship Program at Marshall Space Flight Center (MSFC) is given. Weibull density functions, reliability analysis, directional solidification, space stations, jet stream, fracture mechanics, composite materials, orbital maneuvering vehicles, stellar winds and gamma ray bursts are among the topics discussed

Visualisation of multi-dimensional medical images with application to brain electrical impedance tomography

Medical imaging plays an important role in modem medicine. With the increasing complexity and information presented by medical images, visualisation is vital for medical research and clinical applications to interpret the information presented in these images. The aim of this research is to investigate improvements to medical image visualisation, particularly for multi-dimensional medical image datasets. A recently developed medical imaging technique known as Electrical Impedance Tomography (EIT) is presented as a demonstration. To fulfil the aim, three main efforts are included in this work. First, a novel scheme for the processmg of brain EIT data with SPM (Statistical Parametric Mapping) to detect ROI (Regions of Interest) in the data is proposed based on a theoretical analysis. To evaluate the feasibility of this scheme, two types of experiments are carried out: one is implemented with simulated EIT data, and the other is performed with human brain EIT data under visual stimulation. The experimental results demonstrate that: SPM is able to localise the expected ROI in EIT data correctly; and it is reasonable to use the balloon hemodynamic change model to simulate the impedance change during brain function activity. Secondly, to deal with the absence of human morphology information in EIT visualisation, an innovative landmark-based registration scheme is developed to register brain EIT image with a standard anatomical brain atlas. Finally, a new task typology model is derived for task exploration in medical image visualisation, and a task-based system development methodology is proposed for the visualisation of multi-dimensional medical images. As a case study, a prototype visualisation system, named EIT5DVis, has been developed, following this methodology. to visualise five-dimensional brain EIT data. The EIT5DVis system is able to accept visualisation tasks through a graphical user interface; apply appropriate methods to analyse tasks, which include the ROI detection approach and registration scheme mentioned in the preceding paragraphs; and produce various visualisations

Investigating ray tracing algorithms and data structures in the context of visibility.

Ray tracing is a popular rendering method with built in visibility determination. However, the computational costs are significant. To reduce them, there has been extensive research leading to innovative data structures and algorithms that optimally utilize both object and image coherence. Investigating these from a visibility determination context without considering further optical effects is the main motivation of the research. Three methods - one structure and two coherent tree traversal algorithms - are discussed. While the structure aims to increase coherence, the algorithms aim to optimise utilization of coherence provided by ray tracing structures (kd-trees, octrees). RBSF trees - Restricted Binary Space Partitioning Trees - build upon the research in ray tracing with kd-trees. A higher degree of freedom for split plane selection increases object coherence implying a reduction in the number of node traversals and triangle intersections for most scenes. Consequently, reduced ray casting times for scenes with predominantly non-axis-aligned triangles is observed. Coherent Rendering is a rendering method that shows improved complexity, but at an absolute performance that is much slower than packet ray tracing. However, since it led to the creation of the Row Tracing' algorithm, it is described briefly. Row Tracing can be considered as an adaptation of Coherent Rendering, scanline rendering or packet ray tracing. One row of the image is considered and its pixels are determined. Similar to Coherent Rendering, an adapted version of Hierarchical Occlusion Maps is used to identify and skip occluded nodes. To maximize utilisation of coherence, the method is extended so that several adjacent rows are traversed through the tree. The two versions of Row Tracing demonstrate excellent performance, exceeding that of packet ray tracing. Further, it is shown that for larger models (2 million+ triangles). Row Tracing and Packet Row Tracing significantly outperform Z-buffer based methods (OpenGL). Row tracing show's scalability over scene sizes leading to a rendering method that has fast rendering times for both large and small models. In addition it has excellent parallelisation properties allowing utilisation of multiple cores with ease. Thus, the Row Tracing and Packet Row Tracing algorithms can be considered as the significant contributions of the Ph.D. These data structures and algorithms demonstrate that ray tracing data structures and adaptations of ray tracing algorithms exhibit excellent potential in a visibility context