WSCG '2008: Full Papers
Permanent URI for this collection
Browse
Recent Submissions
Item Perception-Based Integration of Vision and Touch in Virtual Environments(Václav Skala - UNION Agency, 2008) Lécuyer, A.; Cunningham, Steve; Skala, VáclavThe technological progresses that were achieved concerning Virtual Reality displays for the eyes of the user (head mounted displays, large projection screens, workbenches, CAVE, etc) as well as for his/her hands (forcefeedback arms or joysticks, exoskeleton gloves, tactile matrices, etc) allow today to simulate visual and haptic sensations that are very close from sensations generated by the visualization or interaction with real objects, in real situations. However, even though the realism of each one of these stimuli taken separately improves regularly and spectacularly, the coupling and the combination of multiple stimulations on different sensory channels raise numerous novel and complex questions for virtual reality applications. For instance, how to share and spread the sensory information of the virtual world on the multiple sensory channels at disposal? How to synchronize the separated sources of sensory information spatially and temporally? Are there any preferential combinations of sensory information? More generally, how do humans perceive and integrate information provided by different sensory channels? What are the perceptual and cognitive mechanisms that are involved? Can we take advantage from them when designing multi-sensory virtual environments? In addition to these numerous questions, a classical perceptual phenomenon can also strike our attention: the sensory illusions. Sensory illusions illustrate the plasticity of our brain and reveal its surprising and regular mistakes of interpretation of sensory information. The question of sensory illusions is a central question in virtual realitywhich can be seen as a vast operation aiming at generating the illusion of another reality, of another tangible universe. During the past decade, we have developed and proposed a novel concept of haptic feedback in virtual reality called 'pseudo-haptic feedback'. Pseudo-haptic feedback is meant to simulate haptic sensations in virtual environments using properties of the human perception. Pseudo-haptic feedback uses visual feedback and borders on sensory illusion. It has been already used to simulate various haptic properties such as: stiffness or mass of virtual objects, texture of images, etc. It was also successfully implemented in various applications, such as within a virtual environment for the vocational training to milling machines, or a medical simulator for the training to regional anaesthesia procedures. In this talk, we will first depict related work in the field of human perception, integration of vision and touch, and haptic illusions. Then we will report on experiments and on haptic properties that have been simulated to date using pseudo-haptic feedback. We will assess the potential applications of pseudo-haptic feedback in virtual reality and we will draw lessons from our past experience in implementing and evaluating visuo-haptic virtual environments.
Item The Visual Computing of Projector-Camera Systems(Václav Skala - UNION Agency, 2008) Bimber, O.; Cunningham, Steve; Skala, VáclavTheir increasing capabilities and declining cost make video projectors widespread and established presentation tools. Being able to generate images that are larger than the actual display device virtually anywhere is an interesting feature for many applications that cannot be provided by desktop screens. Several research groups discover this potential by applying projectors in unconventional ways to develop new and innovative information displays that go beyond simple screen presentations. Todays projectors are able to modulate the displayed images spatially and temporally. Synchronized camera feedback is analyzed to support a real-time image correction that enables projections on complex everyday surfaces that are not bound to projector-optimized canvases or dedicated screen configurations. In this talk I will give an overview over our projector-camera-based image correction techniques for geometric warping, radiometric compensation, reduction of global illumination (such as inter-reflections) or view-dependent effects (such as specular reflections), increasing focal depth, and embedding imperceptible codes with a single or with multiple projection units. Thereby, GPU-based real-time rendering and computer vision on graphics hardware are tightly coupled. Such techniques have proved to be useful tools for many real-world applications. Examples include ad-hoc stereoscopic VR/AR visualizations within everyday environments, quality improvements for (semi-)immersive VR projection displays, on-site architectural simulations, augmentations of museum artifacts, video installations in cultural heritage sites, projections onto stage settings during live performances, presentations using mobile (pocket) projectors, outdoor advertisement displays, digital illumination and projections in modern television studios, computer games, and more.Item Virtual Iraq: Initial Results from a VR Exposure Therapy Application for Combat-Related Post Traumatic Stress Disorder(Václav Skala - UNION Agency, 2008) Rizzo, A.; Pair, J.; Graap, K.; Rothbaum, B. O.; Difede, J.; Reger, G.; Parsons, T.; Mclay, R. N.; Perlman, K.; Cunningham, Steve; Skala, VáclavThe 'Virtual Iraq' VR environment is designed to be an immersive tool foruse as an Exposure Therapy treatment tool for combat related PTSD. The application consists of a series of virtual scenarios designed to represent relevant contexts for VR exposure therapy, including city and desert road environments. In addition to the visual stimuli presented in the VR HMD, directional 3D audio, vibrotactile and olfactory stimuli of relevance can be delivered. Stimulus presentation is controlled by the clinician via a separate 'wizard of oz'; interface, with the clinician in full audio contact with the patient. The presentation at the conference will detail the results of our research and clinical treatment protocols as they stand at that time. Presently, an open clinical trial to evaluate our system’s efficacy for PTSD treatment with military personnel is being conducted at the Naval Medical Center San Diego and at Ft. Lewis, Washington, and a randomized controlled trial comparing VR alone and VRcycloserine is in progress at Emory University. Ten other test sites are now on line between now and the conference addressing a variety of research questions involving assessment of PTSD, physiological markers of the disorder, impact of multiple trauma events, and an fMRI study. Thus far, eight male and female treatment completers (out of 11) at two of the treatment sites have shown clinically significant improvements at posttreatment, with these patients now no longer meeting PTSD criteria. Due to the challenges for treatment of this disorder, we are encouraged by these early results.Item Spectral Modeling and Virtual Restoration on a Polychrome Medieval Sculpture(Václav Skala - UNION Agency, 2008) Dumazet, Sylvain; Callet, Patrick; Genty, Ariane; Cunningham, Steve; Skala, VáclavThe presented work is led in the framework of a general collaboration between three academic labs, industrial partners and Cultural institutions (Centre des Monuments Nationaux, Louvre museum). Such a pluridisciplinary work always in progress at Ecole Centrale Paris deals with 3D digitization, simulation, rapid prototyping, virtual restoration applied on a french medieval sculpture. The main purpose is to virtually represent a polychrome statue of the XIIIth century in high quality spectral rendering, to simulate its visual and original appearance at that period. The complete process used throughout all the phases of the project mainly involves optical devices that ensure no physical contact with the museum object. This article describes the complete chain of engineering resources and the main models we used for accomplishing our objective. From 3D capture without contact to plaster replica, the complete process will be described and illustrated with images and objects during the conference. Some sequences extracted from the didactic and scientific movies produced will also be presented.Item Geometric Feature Deletion Through Freeform Feature Recognition(Václav Skala - UNION Agency, 2008) Langerak, Thomas R.; Cunningham, Steve; Skala, VáclavThe deletion of geometric features is a much used operation in the process of shape modeling; by deleting geometric features, the smoothness of a surface can be increased. In this paper, a new method is presented for the deletion of geometric features, which is based on a morphological understanding of the feature. The method first parameterizes the feature and then deletes it using a parameter-based shape manipulation. The advantage of this new method is that a geometric feature can be deleted while maintaining the semantics of both the feature and its embedding shape. To be able to parameterize the feature, an improved version of an existing evolutionary feature recognition procedure is developed, which constructs a feature template that matches a feature on the target model. Application examples are given and the robustness of the method is discussed.Item Acoustic Modeling of Reverberation using Smoothed Particle Hydrodynamics(Václav Skala - UNION Agency, 2008) Wolfe, Charles Thomas; Semwal, Sudhanshu Kumar; Cunningham, Steve; Skala, VáclavCurrent methods for digital acoustic modeling of reverberation can be categorized into two main areas: DSP algorithms and sound tracing algorithms. DSP algorithms are usually chosen for their speed and ease of use. DSP methods are generally fast, but do not accurately represent complex environments. Sound tracing algorithms, such as beam tracing, accurately model static environments but have difficulty with complex and/or moving geometry. A Computation Fluid Dynamics (CFD) method called Smoothed Particle Hydrodynamics (SPH) has recently gained interest as a method for accurately simulating fluid flow using discrete particles. This paper extends SPH by adding the ability to model sound wave propagation through fluids. A generalized method that integrates sound generation and reception is presented in this paper. This method provides a basis for acoustic sound effects, such as reverberation.Item A Generalized Light-Field API and Management System(Václav Skala - UNION Agency, 2008) Blasco, Joan; Escrivà, Miguel; Abad, Francisco; Quirós, Ricardo; Camahort, Emilio; Vivó, Roberto; Cunningham, Steve; Skala, VáclavLight fields are a computer graphics modeling technique that represents objects using radiance samples instead of geometry. Radiance samples may be stored as sets of images or 4D arrays of pixel values. Light fields have various advantages: their rendering complexity only depends on the output image’s, they can represent sophisticated illumination effects, and they are well-suited for display using autostereoscopic devices. To study different light-field representations, as well as their capture, generation, resampling, storage, composition, rendering and display, we have developed a light-field based API and graphics system. The system supports models based on different light-field parameterizations, as well as different generation and capture methods, rendering methods, data caching algorithms and output displays. The API will also support hybrid light-field and geometry based models, as well as light-field resampling and composition.Item Spatially constrained model for mean shift(Václav Skala - UNION Agency, 2008) Lucena, M. J.; Fuertes, J. M.; Pérez de la Blanca, N.; Cunningham, Steve; Skala, VáclavThis paper presents a multiple model real-time tracking technique based on the mean-shift algorithm. The proposed approach incorporates spatial information from several connected regions into the histogram-based representation model of the target, and enables multiple models to be used to represent the same object. The use of several regions to capture the color spatial information into a single combined model, allow us to increase the object tracking efficiency. We use a model selection function that takes into account both the similarity of the model with the information present in the image, and the target dynamics. In the tracking experiments presented, our method successfully coped with lighting changes, occlusion, and clutter.Item Human Skeletal and Muscle Deformation Animation Using Motion Capture Data(Václav Skala - UNION Agency, 2008) Bayer, Ali Orkan; Sevinç, Ayça Müge; Can, Tolga; Cunningham, Steve; Skala, VáclavHuman character animation has problems of unrealistic motion and unrealistic skin deformation. In this study, we present an application of motion capture data for generating realistic human character animation using anatomically correct skeleton and muscle models. For this purpose, we attach a skeleton model to the motion data and then construct and attach a set of muscle models to the underlying skeleton. Deformation under isotonic contractions are modeled using a number of geometric primitives. As a result, we have implemented a toolkit where animations can be viewed and recorded as a video file. In order to demonstrate the use of the toolkit, we have produced a number of short movies for entertainment purposes. The generated muscle deformations are realistic. As future work, we plan to apply skin to our model and generate realistic looking skin deformations.Item Comparative Evaluation of Random Forest and Fern Classifiers for Real-Time Feature Matching(Václav Skala - UNION Agency, 2008) Barandiaran, Iñigo; Cottez, Charlote; Paloc, Céline; Graña, Manuel; Cunningham, Steve; Skala, VáclavFeature or keypoint matching is a critical task in many computer vision applications, such as optical 3D reconstruction or optical markerless tracking. These applications demand very accurate and fast matching techniques. We present an evaluation and comparison of two keypoint matching strategies based on supervised classification for markerless tracking of planar surfaces. We have applied these approaches on an augmented reality prototype for indoor and outdoor design review.Item New method to optimize Force-directed layouts of large graphs(Václav Skala - UNION Agency, 2008) Dodo, Meva; Andriamanampisoa, Fenohery; Torguet, Patrice; Jessel, Jean Pierre; Cunningham, Steve; Skala, VáclavThis paper describes a novel method to optimize the force-directed placement algorithm for 3D drawing of large graphs. The main idea behind our approach consists in optimizing the layout by equitably distributing vertices in space. We consider the largest sphere inscribed in the 3D space and the vertices are then assigned random initial positions that are improved by force-directed placement. In order to ensure the effectiveness of the algorithm, we propose a new energy function minimization which uses the conjugated gradient of Fletcher-Reeves. Our algorithm is not only addressed to general undirected graphs but it also produces good layouts for large trees. This work is motivated by our need to offer 3D visualization tools for large computing networks but this first phase will be focused on the graph representation.Item Visual simulation of Civil Engineering activities: Didactic virtual models(Václav Skala - UNION Agency, 2008) Sampaio, Alcínia Zita; Henriques, Pedro Gameiro; Cunningham, Steve; Skala, VáclavThree-dimensional geometric models have been used to present architectural and engineering works, showing their final configuration. But, when the clarification of a detail or the constitution of a construction step in needed, these models are not appropriate because they do not allow the observation of the construction activity. Models that could present dynamically changes of the building geometry are a good support on education in civil engineering domain. Techniques of geometric modeling and virtual reality were used to obtain interactive models that could visually simulate the construction activity. The applications explain the construction work of a cavity wall and a bridge. These models allow the visualization of the physical progression of the work following a planned construction sequence, the observation of details of the form of every component of the works and support the study of the type and method of operation of the equipment applied in the construction. The models present distinct advantage as educational aids in first-degree courses in Civil Engineering. The use of Virtual Reality techniques in the development of educational applications brings new perspectives to the teaching of subjects related to the field of civil construction.Item From Bag of Categories to Tree of Object Recognition(Václav Skala - UNION Agency, 2008) Wang, Haijing; Zhang, Tianwen; Li, Peihua; Cunningham, Steve; Skala, VáclavTo recognize different category of objects, multiclass categorization problem is often reduced to multiple binary problems. Traditional approaches require training different classifiers for each category. This can be slow and the performance of learned single classifier is poor for limited training samples. We present a multiclass object recognition tree, in which the leaf node and the non-leaf node correspond to one category and a bag of categories, respectively. Each non-leaf node captures the shared features of a bag of categories. Each node also holds a group of classifiers trained by AdaBoost, to discriminate the categories locating at its left and right child node. Recognition is then a process to find a path from the root to a leaf, which represents a unique category. The very promising result on Caltech 101 dataset shows the robustness of the proposed approach.Item On the use of a palm computer for design review interaction in a virtual room(Václav Skala - UNION Agency, 2008) Pignatel, A.; Farella, E.; Brevi, F.; Benini, L.; Gaiani, M.; Cunningham, Steve; Skala, VáclavIncreasingly often the use of photorealistic models for design review processes involves the setup of special rooms, fully dedicated to visualize digital models onto large display, the so called CADwall. In this scenario an effective interaction with virtual prototypes is a basic need, but it is almost always based on traditional input devices, such as mouse and keyboard. The design review process is usually led by a chief designer, but the use of traditional interaction tools requires an additional operator. This operator is guided by the chief designer through vocal inputs in a slow, misleading and inefficient way. In this paper we propose a solution based on a handheld device and an inertial sensor node, with a graphic interface that allows a direct interaction with 3-D digital models inside virtual rooms with large displays.Item Fluid Dynamic Simulation for Cutting in Virtual Environment(Václav Skala - UNION Agency, 2008) Rianto, Sugeng; Li, Ling; Hartley, Bruce; Cunningham, Steve; Skala, VáclavIn this paper, we introduce a 3D fluid dynamics solver for real-time interactions in virtual environment. We approach the solution of differential equations based on the cubic interpolated propagation (CIP) technique on GPU. Since the CIP combine the solution for fluid equations and their interactions with the environment together, the Navier-Stokes equation can be solved efficiently. Furthermore, to achieve high performance results without involving a supercomputer, we take advantage of the parallelism and programmability of the GPU. Simulation is performed on pixels that can be considered to be a grid of cells; therefore processing on multiple vertices and pixels can be done simultaneously in parallel. This strategy is effective enough to simulate fluid dynamic model for real-time virtual cutting in 3D computer graphic. Experimental results demonstrate that the skin cutting followed by blood flowing over the anatomical surface run smoothly in a real-time interaction and realistic visual effect is achieved.Item Discovering the Covered: Ghost-Views in Information Visualization(Václav Skala - UNION Agency, 2008) Luboschik, Martin; Schumann, Heidrun; Cunningham, Steve; Skala, VáclavA not negligible number of information visualization techniques uses 3D-geometry to visualize data and structures. Thereby, constantly growing data volumes influence the final visual representation and often result in the occlusion of certain items. Therefore, different approaches have been developed that mainly manipulate item positions to uncover specific items of interest or otherwise use filtering and information hiding to reduce the amount of visible items. This paper presents a novel method to adapt 3D-views from information visualization by the use of the well-known illustrative technique ghost-view to successfully address this occlusion problem. Applying ghost-views to 3D information visualization techniques ensures the visibility of selected items by view-dependently manipulating the transparency of unselected data: without any manipulation of positions or continuous context suppression. Our approach is applicable to most 3D visualization techniques. It is interactive and easy to adapt to existing visualization environments.Item A Hybrid Technique for Creating Meaningful Abstractions of Dynamic 3D Scenes in Real-Time(Václav Skala - UNION Agency, 2008) Redmond, Niall; Dingliana, John; Cunningham, Steve; Skala, VáclavWe present an approach for creating non-photorealistic renderings of 3D scenes in real-time. We employ a hybrid system which uses both image-space and object-space techniques for creating fast and effective results. A reliable method of edge detection is presented to find all important edges within a scene. This edge detection technique is combined with a painterly renderer to render the scene using different levels of abstraction. This is used to increase the saliency of important objects and remove extraneous detail. 3D object information is used to apply an object-based segmentation technique which allows each scene object to be rendered using a single abstraction level depending on its scene importance. The abstraction techniques are implemented on the GPU which helps the system achieve interactive rates.Item Dynamic Mesh Refinement on GPU using Geometry Shaders(Václav Skala - UNION Agency, 2008) Lorenz, Haik; Döllner, Jürgen; Cunningham, Steve; Skala, VáclavThis paper presents a real-time rendering technique for dynamic, incremental 3D mesh refinement. The technique can be applied to any triangulated 3D mesh with arbitrary topology and connectivity. The functionality relies on geometry shaders that are used to amplify or remove geometry based on precalculated refinement patterns. For each triangle, the instantiated refinement pattern is selected dynamically. Due to limitations of current hardware, on-the-fly pattern instantiation cannot be implemented on the GPU. Instead, the complete refined mesh must be generated through pattern copying. We propose an incremental approach where the refined mesh is generated by using the previous refined mesh as primitive source. This algorithm runs exclusively on the GPU and requires no continuous data exchange between CPU and GPU. Due to the necessary mesh generation, the approach is particularly suitable for applications with small refinement levels. It complements traditional pattern-based refinement approaches that deliver high throughput for large refinement levels, but incur a substantial CPU-GPU communication overhead otherwise. Interesting applications include view-dependent mesh smoothing and interactive non-planar projections. In these areas, our algorithm enables efficient vertex-based implementations due to adaptive refinement.Item Automatic Axis Extraction from “Tubular” Structures In CT Images- An Application in Virtual Colonoscopy(Václav Skala - UNION Agency, 2008) Hernandez, José Tiberio; Calderon, Juan Manuel; Cunningham, Steve; Skala, VáclavThis paper presents a new method for axis extraction from “tubular” structures in CT images. The axis is important in virtual colonoscopy systems because it offers more efficient measurement features and better interactive visualization possibilities. The proposed method is based on the “pseudo-tubular” structure of the Colon. To find a good estimation of the Colon axis, the method is organized in two steps: In the first step, the voxels are organized in sequential clusters along the structure using a region-growing strategy and a cylindricity criterion. Each cluster has a distinct point (which is a good candidate to be part of the axis, identified by the cylindricity criterion), and an internal partial ordering of the cluster’s voxels. This information structure allows us, in the second step, to propose three instances (one per principal coordinate axis) of an estimation problem to be solved with the Takagi-Sugeno- Kang Method (TSK). Based in the resulting solutions it is possible to build a piece-wise linear estimation of the colon axis. This method has produced good results. It is robust in face of the “pseudo-tubular” shape of the colon. It has been tested on a set of Colon CT images from previously prepared patients. The results are illustrated with animations of virtual colonoscopy and a set of measurements and visualizations. Medical practitioners had a good perception of the method’s potential in the field of virtual colonoscopy applications.Item Automatic Zoom and Pseudo Haptics to Support Semiautomatic Segmentation Tasks(Václav Skala - UNION Agency, 2008) Schoor, Wolfram; Bollenbeck, Felix; Hofmann, Marc; Mecke, Rüdiger; Seiffert, Udo; Preim, Bernhard; Cunningham, Steve; Skala, VáclavThis paper presents a new technique for navigating large amounts of biological image data during segmentation. Digitized microtome tissue slices of barley grains constitute the image data. Automatic zoom is dependent on mouse speed, thus enabling users to navigate an image more efficiently and with a tighter focus during segmentation. The user remains oriented and smoothly moves through the data. Furthermore, pseudo haptic feedback based on image cost map data compensates for user inaccuracies generated, for example, by shaky hands. A prototype was implemented and tested. An informal usability study revealed that users are inclined to prefer automatic zooming and pseudo haptics for semiautomatic segmentation tasks.
