A Framework for Dynamic Terrain with Application in Off-road Ground Vehicle Simulations

The dissertation develops a framework for the visualization of dynamic terrains for use in interactive real-time 3D systems. Terrain visualization techniques may be classified as either static or dynamic. Static terrain solutions simulate rigid surface types exclusively; whereas dynamic solutions can also represent non-rigid surfaces. Systems that employ a static terrain approach lack realism due to their rigid nature. Disregarding the accurate representation of terrain surface interaction is rationalized because of the inherent difficulties associated with providing runtime dynamism. Nonetheless, dynamic terrain systems are a more correct solution because they allow the terrain database to be modified at run-time for the purpose of deforming the surface. Many established techniques in terrain visualization rely on invalid assumptions and weak computational models that hinder the use of dynamic terrain. Moreover, many existing techniques do not exploit the capabilities offered by current computer hardware. In this research, we present a component framework for terrain visualization that is useful in research, entertainment, and simulation systems. In addition, we present a novel method for deforming the terrain that can be used in real-time, interactive systems. The development of a component framework unifies disparate works under a single architecture. The high-level nature of the framework makes it flexible and adaptable for developing a variety of systems, independent of the static or dynamic nature of the solution. Currently, there are only a handful of documented deformation techniques and, in particular, none make explicit use of graphics hardware. The approach developed by this research offloads extra work to the graphics processing unit; in an effort to alleviate the overhead associated with deforming the terrain. Off-road ground vehicle simulation is used as an application domain to demonstrate the practical nature of the framework and the deformation technique. In order to realistically simulate terrain surface interactivity with the vehicle, the solution balances visual fidelity and speed. Accurately depicting terrain surface interactivity in off-road ground vehicle simulations improves visual realism; thereby, increasing the significance and worth of the application. Systems in academia, government, and commercial institutes can make use of the research findings to achieve the real-time display of interactive terrain surfaces

Finding failures from passed test cases: Improving the pattern classification approach to the testing of mesh simplification programs

Mesh simplification programs create three-dimensional polygonal models similar to an original polygonal model, and yet use fewer polygons. They produce different graphics even though they are based on the same original polygonal model. This results in a test oracle problem. To address the problem, our previous work has developed a technique that uses a reference model of the program under test to train a classifier. Using such an approach may mistakenly mark a failure-causing test case as passed. It lowers the testing effectiveness of revealing failures. This paper suggests piping the test cases marked as passed by a statistical pattern classification module to an analytical metamorphic testing (MT) module. We evaluate our approach empirically using three subject programs with over 2700 program mutants. The result shows that, using a resembling reference model to train a classifier, the integrated approach can significantly improve the failure detection effectiveness of the pattern classification approach. We also explain how MT in our design trades specificity for sensitivity. Copyright © 2009 John Wiley & Sons, Ltd.link_to_subscribed_fulltex

The Optimization of Geotechnical Site Investigations for Pile Design in Multiple Layer Soil Profiles Using a Risk-Based Approach

The testing of subsurface material properties, i.e. a geotechnical site investigation, is a crucial part of projects that are located on or within the ground. The process consists of testing samples at a variety of locations, in order to model the performance of an engineering system for design processes. Should these models be inaccurate or unconservative due to an improper investigation, there is considerable risk of consequences such as structural collapse, construction delays, litigation, and over-design. However, despite these risks, there are relatively few quantitative guidelines or research items on informing an explicit, optimal investigation for a given foundation and soil profile. This is detrimental, as testing scope is often minimised in an attempt to reduce expenditure, thereby increasing the aforementioned risks. This research recommends optimal site investigations for multi-storey buildings supported by pile foundations, for a variety of structural configurations and soil profiles. The recommendations include that of the optimal test type, number of tests, testing locations, and interpretation of test data. The framework consists of a risk-based approach, where an investigation is considered optimal if it results in the lowest total project cost, incorporating both the cost of testing, and that associated with any expected negative consequences. The analysis is statistical in nature, employing Monte Carlo simulation and the use of randomly generated virtual soils through random field theory, as well as finite element analysis for pile assessment. A number of innovations have been developed to assist the novel nature of the work. For example, a new method of producing randomly generated multiple-layer soils has been devised. This work is the first instance of site investigations being optimised in multiple-layer soils, which are considerably more complex than the single-layer soils examined previously. Furthermore, both the framework and the numerical tools have been themselves extensively optimised for speed. Efficiency innovations include modifying the analysis to produce re-usable pile settlement curves, as opposed to designing and assessing the piles directly. This both reduces the amount of analysis required and allows for flexible post-processing for different conditions. Other optimizations include the elimination of computationally expensive finite element analysis from within the Monte Carlo simulations, and additional minor improvements. Practicing engineers can optimise their site investigations through three outcomes of this research. Firstly, optimal site investigation scopes are known for the numerous specific cases examined throughout this document, and the resulting inferred recommendations. Secondly, a rule-of-thumb guideline has been produced, suggesting the optimal number of tests for buildings of all sizes in a single soil case of intermediate variability. Thirdly, a highly efficient and versatile software tool, SIOPS, has been produced, allowing engineers to run a simplified version of the analysis for custom soils and buildings. The tool can do almost all the analysis shown throughout the thesis, including the use of a genetic algorithm to optimise testing locations. However, it is approximately 10 million times faster than analysis using the original framework, running on a single-core computer within minutes.Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 202

Collaborative visualization environment using P2P technology and ellipsoidal mesh partitioning

Ph.DDOCTOR OF PHILOSOPH

Management of spatial data for visualization on mobile devices

Vector-based mapping is emerging as a preferred format in Location-based Services(LBS), because it can deliver an up-to-date and interactive map visualization. The Progressive Transmission(PT) technique has been developed to enable the ecient transmission of vector data over the internet by delivering various incremental levels of detail(LoD). However, it is still challenging to apply this technique in a mobile context due to many inherent limitations of mobile devices, such as small screen size, slow processors and limited memory. Taking account of these limitations, PT has been extended by developing a framework of ecient data management for the visualization of spatial data on mobile devices. A data generalization framework is proposed and implemented in a software application. This application can signicantly reduce the volume of data for transmission and enable quick access to a simplied version of data while preserving appropriate visualization quality. Using volunteered geographic information as a case-study, the framework shows exibility in delivering up-to-date spatial information from dynamic data sources. Three models of PT are designed and implemented to transmit the additional LoD renements: a full scale PT as an inverse of generalisation, a viewdependent PT, and a heuristic optimised view-dependent PT. These models are evaluated with user trials and application examples. The heuristic optimised view-dependent PT has shown a signicant enhancement over the traditional PT in terms of bandwidth-saving and smoothness of transitions. A parallel data management strategy associated with three corresponding algorithms has been developed to handle LoD spatial data on mobile clients. This strategy enables the map rendering to be performed in parallel with a process which retrieves the data for the next map location the user will require. A viewdependent approach has been integrated to monitor the volume of each LoD for visible area. The demonstration of a exible rendering style shows its potential use in visualizing dynamic geoprocessed data. Future work may extend this to integrate topological constraints and semantic constraints for enhancing the vector map visualization

Patient-specific simulation environment for surgical planning and preoperative rehearsal

Surgical simulation is common practice in the fields of surgical education and training. Numerous surgical simulators are available from commercial and academic organisations for the generic modelling of surgical tasks. However, a simulation platform is still yet to be found that fulfils the key requirements expected for patient-specific surgical simulation of soft tissue, with an effective translation into clinical practice. Patient-specific modelling is possible, but to date has been time-consuming, and consequently costly, because data preparation can be technically demanding. This motivated the research developed herein, which addresses the main challenges of biomechanical modelling for patient-specific surgical simulation. A novel implementation of soft tissue deformation and estimation of the patient-specific intraoperative environment is achieved using a position-based dynamics approach. This modelling approach overcomes the limitations derived from traditional physically-based approaches, by providing a simulation for patient-specific models with visual and physical accuracy, stability and real-time interaction. As a geometrically- based method, a calibration of the simulation parameters is performed and the simulation framework is successfully validated through experimental studies. The capabilities of the simulation platform are demonstrated by the integration of different surgical planning applications that are found relevant in the context of kidney cancer surgery. The simulation of pneumoperitoneum facilitates trocar placement planning and intraoperative surgical navigation. The implementation of deformable ultrasound simulation can assist surgeons in improving their scanning technique and definition of an optimal procedural strategy. Furthermore, the simulation framework has the potential to support the development and assessment of hypotheses that cannot be tested in vivo. Specifically, the evaluation of feedback modalities, as a response to user-model interaction, demonstrates improved performance and justifies the need to integrate a feedback framework in the robot-assisted surgical setting.Open Acces