413 research outputs found
Stereoscopic viewing, roughness and gloss perception
This thesis presents a novel investigation into the effect stereoscopic vision has upon the
strength of perceived gloss on rough surfaces. We demonstrate that in certain cases
disparity is necessary for accurate judgements of gloss strength.
We first detail the process we used to create a two-level taxonomy of property terms,
which helped to inform the early direction of this work, before presenting the eleven
words which we found categorised the property space. This shaped careful examination
of the relevant literature, leading us to conclude that most studies into roughness, gloss,
and stereoscopic vision have been performed with unrealistic surfaces and physically
inaccurate lighting models.
To improve on the stimuli used in these earlier studies, advanced offline rendering
techniques were employed to create images of complex, naturalistic, and realistically
glossy 1/fβ noise surfaces. These images were rendered using multi-bounce path tracing
to account for interreflections and soft shadows, with a reflectance model which
observed all common light phenomena. Using these images in a series of
psychophysical experiments, we first show that random phase spectra can alter the
strength of perceived gloss. These results are presented alongside pairs of the surfaces
tested which have similar levels of perceptual gloss. These surface pairs are then used to
conclude that naïve observers consistently underestimate how glossy a surface is
without the correct surface and highlight disparity, but only on the rougher surfaces
presented
Ambient occlusion and shadows for molecular graphics
Computer based visualisations of molecules have been produced as early as the 1950s to aid researchers in their understanding of biomolecular structures. An important consideration for Molecular Graphics software is the ability to visualise the 3D structure of the molecule in a clear manner.
Recent advancements in computer graphics have led to improved rendering capabilities of the visualisation tools. The capabilities of current shading languages allow the inclusion of advanced graphic effects such as ambient occlusion and shadows that
greatly improve the comprehension of the 3D shapes of the molecules.
This thesis focuses on finding improved solutions to the real time rendering of Molecular Graphics on modern day computers. The methods of calculating ambient occlusion and both hard and soft shadows are examined and implemented to give the user a more complete experience when navigating large molecular structures
Sensory Communication
Contains table of contents for Section 2, an introduction and reports on fourteen research projects.National Institutes of Health Grant RO1 DC00117National Institutes of Health Grant RO1 DC02032National Institutes of Health/National Institute on Deafness and Other Communication Disorders Grant R01 DC00126National Institutes of Health Grant R01 DC00270National Institutes of Health Contract N01 DC52107U.S. Navy - Office of Naval Research/Naval Air Warfare Center Contract N61339-95-K-0014U.S. Navy - Office of Naval Research/Naval Air Warfare Center Contract N61339-96-K-0003U.S. Navy - Office of Naval Research Grant N00014-96-1-0379U.S. Air Force - Office of Scientific Research Grant F49620-95-1-0176U.S. Air Force - Office of Scientific Research Grant F49620-96-1-0202U.S. Navy - Office of Naval Research Subcontract 40167U.S. Navy - Office of Naval Research/Naval Air Warfare Center Contract N61339-96-K-0002National Institutes of Health Grant R01-NS33778U.S. Navy - Office of Naval Research Grant N00014-92-J-184
Haptic Interaction with 3D oriented point clouds on the GPU
Real-time point-based rendering and interaction with virtual objects is gaining popularity
and importance as di�erent haptic devices and technologies increasingly provide the basis
for realistic interaction. Haptic Interaction is being used for a wide range of applications
such as medical training, remote robot operators, tactile displays and video games. Virtual
object visualization and interaction using haptic devices is the main focus; this process
involves several steps such as: Data Acquisition, Graphic Rendering, Haptic Interaction
and Data Modi�cation. This work presents a framework for Haptic Interaction using the
GPU as a hardware accelerator, and includes an approach for enabling the modi�cation
of data during interaction. The results demonstrate the limits and capabilities of these
techniques in the context of volume rendering for haptic applications. Also, the use
of dynamic parallelism as a technique to scale the number of threads needed from the
accelerator according to the interaction requirements is studied allowing the editing of
data sets of up to one million points at interactive haptic frame rates
Computer-Assisted Interactive Documentary and Performance Arts in Illimitable Space
This major component of the research described in this thesis is 3D computer
graphics, specifically the realistic physics-based softbody simulation and
haptic responsive environments. Minor components include advanced
human-computer interaction environments, non-linear documentary storytelling,
and theatre performance. The journey of this research has been unusual because
it requires a researcher with solid knowledge and background in multiple
disciplines; who also has to be creative and sensitive in order to combine the
possible areas into a new research direction. [...] It focuses on the advanced
computer graphics and emerges from experimental cinematic works and theatrical
artistic practices. Some development content and installations are completed to
prove and evaluate the described concepts and to be convincing. [...] To
summarize, the resulting work involves not only artistic creativity, but
solving or combining technological hurdles in motion tracking, pattern
recognition, force feedback control, etc., with the available documentary
footage on film, video, or images, and text via a variety of devices [....] and
programming, and installing all the needed interfaces such that it all works in
real-time. Thus, the contribution to the knowledge advancement is in solving
these interfacing problems and the real-time aspects of the interaction that
have uses in film industry, fashion industry, new age interactive theatre,
computer games, and web-based technologies and services for entertainment and
education. It also includes building up on this experience to integrate Kinect-
and haptic-based interaction, artistic scenery rendering, and other forms of
control. This research work connects all the research disciplines, seemingly
disjoint fields of research, such as computer graphics, documentary film,
interactive media, and theatre performance together.Comment: PhD thesis copy; 272 pages, 83 figures, 6 algorithm
HAPTIC AND VISUAL SIMULATION OF BONE DISSECTION
Marco AgusIn bone dissection virtual simulation, force restitution represents the key to realistically mimicking a patient– specific operating environment. The force is rendered using haptic devices controlled by parametrized mathematical models that represent the bone–burr contact. This dissertation presents and discusses a haptic simulation of a bone cutting burr, that it is being developed as a component of a training system for temporal bone surgery. A physically based model was used to describe the burr– bone interaction, including haptic forces evaluation, bone erosion process and resulting debris. The model was experimentally validated and calibrated by employing a custom experimental set–up consisting of a force–controlled robot arm holding a high–speed rotating tool and a contact force measuring apparatus. Psychophysical testing was also carried out to assess individual reaction to the haptic environment. The results suggest that the simulator is capable of rendering the basic material differences required for bone burring tasks. The current implementation, directly operating on a voxel discretization of patientspecific 3D CT and MR imaging data, is efficient enough to provide real–time haptic and visual feedback on a low–end multi–processing PC platform.
Development and validation of real-time simulation of X-ray imaging with respiratory motion
International audienceWe present a framework that combines evolutionary optimisation, soft tissue modelling and ray tracing on GPU to simultaneously compute the respiratory motion and X-ray imaging in real-time. Our aim is to provide validated building blocks with high fidelity to closely match both the human physiology and the physics of X-rays. A CPU-based set of algorithms is presented to model organ behaviours during respiration. Soft tissue deformation is computed with an extension of the Chain Mail method. Rigid elements move according to kinematic laws. A GPU-based surface rendering method is proposed to compute the X-ray image using the Beer-Lambert law. It is provided as an open-source library. A quantitative validation study is provided to objectively assess the accuracy of both components: i) the respiration against anatomical data, and ii) the X-ray against the Beer-Lambert law and the results of Monte Carlo simulations. Our implementation can be used in various applications, such as interactive medical virtual environment to train percutaneous transhepatic cholangiography in interventional radiology, 2D/3D registration, computation of digitally reconstructed radiograph, simulation of 4D sinograms to test tomography reconstruction tools
Investigation of the use of meshfree methods for haptic thermal management of design and simulation of MEMS
This thesis presents a novel approach of using haptic sensing technology combined with virtual environment (VE) for the thermal management of Micro-Electro-Mechanical-Systems (MEMS) design. The goal is to reduce the development cycle by avoiding the costly iterative prototyping procedure. In this regard, we use haptic feedback with virtua lprototyping along with an immersing environment. We also aim to improve the productivity and capability of the designer to better grasp the phenomena operating at the micro-scale level, as well as to augment computational steering through haptic channels. To validate the concept of haptic thermal management, we have implemented a demonstrator with a user friendly interface which allows to intuitively "feel" the temperature field through our concept of haptic texturing. The temperature field in a simple MEMS component is modeled using finite element methods (FEM) or finite difference method (FDM) and the user is able to feel thermal expansion using a combination of different haptic feedback. In haptic application, the force rendering loop needs to be updated at a frequency of 1Khz in order to maintain continuity in the user perception. When using FEM or FDM for our three-dimensional model, the computational cost increases rapidly as the mesh size is reduced to ensure accuracy. Hence, it constrains the complexity of the physical model to approximate temperature or stress field solution. It would also be difficult to generate or refine the mesh in real time for CAD process. In order to circumvent the limitations due to the use of conventional mesh-based techniques and to avoid the bothersome task of generating and refining the mesh, we investigate the potential of meshfree methods in the context of our haptic application. We review and compare the different meshfree formulations against FEM mesh based technique. We have implemented the different methods for benchmarking thermal conduction and elastic problems. The main work of this thesis is to determine the relevance of the meshfree option in terms of flexibility of design and computational charge for haptic physical model
- …