Collision Detection and Merging of Deformable B-Spline Surfaces in Virtual Reality Environment

This thesis presents a computational framework for representing, manipulating and merging rigid and deformable freeform objects in virtual reality (VR) environment. The core algorithms for collision detection, merging, and physics-based modeling used within this framework assume that all 3D deformable objects are B-spline surfaces. The interactive design tool can be represented as a B-spline surface, an implicit surface or a point, to allow the user a variety of rigid or deformable tools. The collision detection system utilizes the fact that the blending matrices used to discretize the B-spline surface are independent of the position of the control points and, therefore, can be pre-calculated. Complex B-spline surfaces can be generated by merging various B-spline surface patches using the B-spline surface patches merging algorithm presented in this thesis. Finally, the physics-based modeling system uses the mass-spring representation to determine the deformation and the reaction force values provided to the user. This helps to simulate realistic material behaviour of the model and assist the user in validating the design before performing extensive product detailing or finite element analysis using commercially available CAD software. The novelty of the proposed method stems from the pre-calculated blending matrices used to generate the points for graphical rendering, collision detection, merging of B-spline patches, and nodes for the mass spring system. This approach reduces computational time by avoiding the need to solve complex equations for blending functions of B-splines and perform the inversion of large matrices. This alternative approach to the mechanical concept design will also help to do away with the need to build prototypes for conceptualization and preliminary validation of the idea thereby reducing the time and cost of concept design phase and the wastage of resources

Doctor of Philosophy

dissertationWhile boundary representations, such as nonuniform rational B-spline (NURBS) surfaces, have traditionally well served the needs of the modeling community, they have not seen widespread adoption among the wider engineering discipline. There is a common perception that NURBS are slow to evaluate and complex to implement. Whereas computer-aided design commonly deals with surfaces, the engineering community must deal with materials that have thickness. Traditional visualization techniques have avoided NURBS, and there has been little cross-talk between the rich spline approximation community and the larger engineering field. Recently there has been a strong desire to marry the modeling and analysis phases of the iterative design cycle, be it in car design, turbulent flow simulation around an airfoil, or lighting design. Research has demonstrated that employing a single representation throughout the cycle has key advantages. Furthermore, novel manufacturing techniques employing heterogeneous materials require the introduction of volumetric modeling representations. There is little question that fields such as scientific visualization and mechanical engineering could benefit from the powerful approximation properties of splines. In this dissertation, we remove several hurdles to the application of NURBS to problems in engineering and demonstrate how their unique properties can be leveraged to solve problems of interest

Technical considerations in designing haptic applications: A case study of laparoscopy surgery simulation with haptic elements

Simulation has been widely used as a tool for training, especially in high risk areas such as in the aerospace, military and medical fields. Surgery is one of the sub areas that has been receiving much attention from researchers due to the ability of simulation to provide a real surgery setting and human organs with appropriate devices to increase the realism. Developing a surgical simulation is a technically complex process since it involves a few components that interact with each other.Thus this necessitates further considerations regarding the issues and challenges in order to produce an accurate and interactive application.Therefore there is a need for a technical solution framework to help a new and novice researcher in this area to get started. This paper discusses the important components of a surgical simulator, together with its issues and challenges.A proposed solution framework, together with the programming or application choices that are available for each of the components, is explained clearly as concluded from the discussion in the previous work.The class structure for the components is shown briefly to give the new researcher an idea of it.It is hoped that this paper will serve as a foundation for new and novice researchers in haptic development specifically and visual informatics generally

Doctor of Philosophy

dissertationVirtual environments provide a consistent and relatively inexpensive method of training individuals. They often include haptic feedback in the form of forces applied to a manipulandum or thimble to provide a more immersive and educational experience. However, the limited haptic feedback provided in these systems tends to be restrictive and frustrating to use. Providing tactile feedback in addition to this kinesthetic feedback can enhance the user's ability to manipulate and interact with virtual objects while providing a greater level of immersion. This dissertation advances the state-of-the-art by providing a better understanding of tactile feedback and advancing combined tactilekinesthetic systems. The tactile feedback described within this dissertation is provided by a finger-mounted device called the contact location display (CLD). Rather than displaying the entire contact surface, the device displays (feeds back) information only about the center of contact between the user's finger and a virtual surface. In prior work, the CLD used specialized two-dimensional environments to provide smooth tactile feedback. Using polygonal environments would greatly enhance the device's usefulness. However, the surface discontinuities created by the facets on these models are rendered through the CLD, regardless of traditional force shading algorithms. To address this issue, a haptic shading algorithm was developed to provide smooth tactile and kinesthetic interaction with general polygonal models. Two experiments were used to evaluate the shading algorithm. iv To better understand the design requirements of tactile devices, three separate experiments were run to evaluate the perception thresholds for cue localization, backlash, and system delay. These experiments establish quantitative design criteria for tactile devices. These results can serve as the maximum (i.e., most demanding) device specifications for tactile-kinesthetic haptic systems where the user experiences tactile feedback as a function of his/her limb motions. Lastly, a revision of the CLD was constructed and evaluated. By taking the newly evaluated design criteria into account, the CLD device became smaller and lighter weight, while providing a full two degree-of-freedom workspace that covers the bottom hemisphere of the finger. Two simple manipulation experiments were used to evaluate the new CLD device

Augmented interaction for custom-fit products by means of interaction devices at low costs

This Ph.D thesis refers to a research project that aims at developing an innovative platform to design lower limb prosthesis (both for below and above knee amputation) centered on the virtual model of the amputee and based on a computer-aided and knowledge-guided approach. The attention has been put on the modeling tool of the socket, which is the most critical component of the whole prosthesis. The main aim has been to redesign and develop a new prosthetic CAD tool, named SMA2 (Socket Modelling Assistant2) exploiting a low-cost IT technologies (e.g. hand/finger tracking devices) and making the user’s interaction as much as possible natural and similar to the hand-made manipulation. The research activities have been carried out in six phases as described in the following. First, limits and criticalities of the already available modeling tool (namely SMA) have been identified. To this end, the first version of SMA has been tested with Ortopedia Panini and the orthopedic research group of Salford University in Manchester with real case studies. Main criticalities were related to: (i) automatic reconstruction of the residuum geometric model starting from medical images, (ii) performance of virtual modeling tools to generate the socket shape, and (iii) interaction mainly based on traditional devices (e.g., mouse and keyboard). The second phase lead to the software reengineering of SMA according to the limits identified in the first phase. The software architecture has been re-designed adopting an object-oriented paradigm and its modularity permits to remove or add new features in a very simple way. The new modeling system, i.e. SMA2, has been totally implemented using open source Software Development Kit-SDK (e.g., Visualization ToolKit VTK, OpenCASCADE and Qt SDK) and based on low cost technology. It includes: • A new module to automatically reconstruct the 3D model of the residual limb from MRI images. In addition, a new procedure based on low-cost technology, such as Microsoft Kinect V2 sensor, has been identified to acquire the 3D external shape of the residuum. • An open source software library, named SimplyNURBS, for NURBS modeling and specifically used for the automatic reconstruction of the residuum 3D model from medical images. Even if, SimplyNURBS has been conceived for the prosthetic domain, it can be used to develop NURBS-based modeling tools for a range of applicative domains from health-care to clothing design. • A module for mesh editing to emulate the hand-made operations carried out by orthopedic technicians during traditional socket manufacturing process. In addition several virtual widgets have been implemented to make available virtual tools similar to the real ones used by the prosthetist, such as tape measure and pencil. • A Natural User Interface (NUI) to allow the interaction with the residuum and socket models using hand-tracking and haptic devices. • A module to generate the geometric models for additive manufacturing of the socket. The third phase concerned the study and design of augmented interaction with particular attention to the Natural User Interface (NUI) for the use of hand-tracking and haptic devices into SMA2. The NUI is based on the use of the Leap Motion device. A set of gestures, mainly iconic and suitable for the considered domain, has been identified taking into account ergonomic issues (e.g., arm posture) and ease of use. The modularity of SMA2 permits us to easily generate the software interface for each device for augmented interaction. To this end, a software module, named Tracking plug-in, has been developed to automatically generate the source code of software interfaces for managing the interaction with low cost hand-tracking devices (e.g., Leap Motion and Intel Gesture Camera) and replicate/emulate manual operations usually performed to design custom-fit products, such medical devices and garments. Regarding haptic rendering, two different devices have been considered, the Falcon Novint, and a haptic mouse developed in-house. In the fourth phase, additive manufacturing technologies have been investigated, in particular FDM one. 3D printing has been exploited in order to permit the creation of trial sockets in laboratory to evaluate the potentiality of SMA2. Furthermore, research activities have been done to study new ways to design the socket. An innovative way to build the socket has been developed based on multi-material 3D printing. Taking advantage of flexible material and multi-material print possibility, new 3D printers permit to create object with soft and hard parts. In this phase, issues about infill, materials and comfort have been faced and solved considering different compositions of materials to re-design the socket shape. In the fifth phase the implemented solution, integrated within the whole prosthesis design platform, has been tested with a transfemoral amputee. Following activities have been performed: • 3D acquisition of the residuum using MRI and commercial 3D scanning systems (low cost and professional). • Creation of the residual limb and socket geometry. • Multi-material 3D printing of the socket using FDM technology. • Gait analysis of the amputee wearing the socket using a markerless motion capture system. • Acquisition of contact pressure between residual limb and a trial socket by means of Teskan’s F-Socket System. Acquired data have been combined inside an ad-hoc developed application, which permits to simultaneously visualize pressure data on the 3D model of the residual lower limb and the animation of gait analysis. Results and feedback have been possible thanks to this application that permits to find correlation between several phases of the gait cycle and the pressure data at the same time. Reached results have been considered very interested and several tests have been planned in order to try the system in orthopedic laboratories in real cases. The reached results have been very useful to evaluate the quality of SMA2 as a future instruments that can be exploited for orthopedic technicians in order to create real socket for patients. The solution has the potentiality to begin a potential commercial product, which will be able to substitute the classic procedure for socket design. The sixth phase concerned the evolution of SMA2 as a Mixed Reality environment, named Virtual Orthopedic LABoratory (VOLAB). The proposed solution is based on low cost devices and open source libraries (e.g., OpenCL and VTK). In particular, the hardware architecture consists of three Microsoft Kinect v2 for human body tracking, the head mounted display Oculus Rift SDK 2 for 3D environment rendering, and the Leap Motion device for hand/fingers tracking. The software development has been based on the modular structure of SMA2 and dedicated modules have been developed to guarantee the communication among the devices. At present, two preliminary tests have been carried out: the first to verify real-time performance of the virtual environment and the second one to verify the augmented interaction with hands using SMA2 modeling tools. Achieved results are very promising but, highlighted some limitations of this first version of VOLAB and improvements are necessary. For example, the quality of the 3D real world reconstruction, especially as far as concern the residual limb, could be improved by using two HD-RGB cameras together the Oculus Rift. To conclude, the obtained results have been evaluated very interested and encouraging from the technical staff of orthopedic laboratory. SMA2 will made possible an important change of the process to design the socket of lower limb prosthesis, from a traditional hand-made manufacturing process to a totally virtual knowledge-guided process. The proposed solutions and results reached so far can be exploited in other industrial sectors where the final product heavily depends on the human body morphology. In fact, preliminary software development has been done to create a virtual environment for clothing design by starting from the basic modules exploited in SMA2

Digital Alchemy: Matter and Metamorphosis in Contemporary Digital Animation and Interface Design

The recent proliferation of special effects in Hollywood film has ushered in an era of digital transformation. Among scholars, digital technology is hailed as a revolutionary moment in the history of communication and representation. Nevertheless, media scholars and cultural historians have difficulty finding a language adequate to theorizing digital artifacts because they are not just texts to be deciphered. Rather, digital media artifacts also invite critiques about the status of reality because they resurrect ancient problems of embodiment and transcendence.In contrast to scholarly approaches to digital technology, computer engineers, interface designers, and special effects producers have invented a robust set of terms and phrases to describe the practice of digital animation. In order to address this disconnect between producers of new media and scholars of new media, I argue that the process of digital animation borrows extensively from a set of preexisting terms describing materiality that were prominent for centuries prior to the scientific revolution. Specifically, digital animators and interface designers make use of the ancient science, art, and technological craft of alchemy. Both alchemy and digital animation share several fundamental elements: both boast the power of being able to transform one material, substance, or thing into a different material, substance, or thing. Both seek to transcend the body and materiality but in the process, find that this elusive goal (realism and gold) is forever receding onto the horizon.The introduction begins with a literature review of the field of digital media studies. It identifies a gap in the field concerning disparate arguments about new media technology. On the one hand, scholars argue that new technologies like cyberspace and digital technology enable radical new forms of engagement with media on individual, social, and economic levels. At the same time that media scholars assert that our current epoch is marked by a historical rupture, many other researchers claim that new media are increasingly characterized by ancient metaphysical problems like embodiment and transcendence. In subsequent chapters I investigate this disparity

Virtual reality for assembly methods prototyping: a review

Assembly planning and evaluation is an important component of the product design process in which details about how parts of a new product will be put together are formalized. A well designed assembly process should take into account various factors such as optimum assembly time and sequence, tooling and fixture requirements, ergonomics, operator safety, and accessibility, among others. Existing computer-based tools to support virtual assembly either concentrate solely on representation of the geometry of parts and fixtures and evaluation of clearances and tolerances or use simulated human mannequins to approximate human interaction in the assembly process. Virtual reality technology has the potential to support integration of natural human motions into the computer aided assembly planning environment (Ritchie et al. in Proc I MECH E Part B J Eng 213(5):461–474, 1999). This would allow evaluations of an assembler’s ability to manipulate and assemble parts and result in reduced time and cost for product design. This paper provides a review of the research in virtual assembly and categorizes the different approaches. Finally, critical requirements and directions for future research are presented

Virtual reality based creation of concept model designs for CAD systems

This work introduces a novel method to overcome most of the drawbacks in traditional methods for creating design models. The main innovation is the use of virtual tools to simulate the natural physical environment in which freeform. Design models are created by experienced designers. Namely, the model is created in a virtual environment by carving a work piece with tools that simulate NC milling cutters. Algorithms have been developed to support the approach, in which the design model is created in a Virtual Reality (VR) environment and selection and manipulation of tools can be performed in the virtual space. The desianer\u27s hand movements generate the tool trajectories and they are obtained by recording the position and orientation of a hand mounted motion tracker. Swept volumes of virtual tools are generated from the geometry of the tool and its trajectories. Then Boolean operations are performed on the swept volumes and the initial virtual stock (work piece) to create the design model. Algorithms have been developed as a part of this work to integrate the VR environment with a commercial CAD/CAM system in order to demonstrate the practical applications of the research results. The integrated system provides a much more efficient and easy-to-implement process of freeform model creation than employed in current CAD/CAM software. It could prove to be the prototype for the next-generation CAD/CAM system