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Rhinosurgical therapy planning via endonasal airflow simulation†

computer Aided Surgery 2000年第3期5卷

作者： Uli Bockholt Dipl.-Math. Gunter Mlynski M.D. Wolfgang Müller Dipl.-Inf. Gerrit Voss Dipl.-Inf. Darmstadt University of Technology Interactive Graphics Systems Group (GRIS) Darmstadt ENT-Clinic Ernst-Moritz-Arndt University Greifswald Greifswald and Fraunhofer Institute for Computer Graphics (Fraunhofer-IGD) Department of Visualization & Virtual Reality Darmstadt Germany

Nowadays, Computational Fluid Dynamics (CFD) methods play an important part in the production process of the automotive industry. Progress in recent years has made possible highly sophisticated airflow-simulation models that are used in engineering for optimization and verification of aerodynamics. The key purpose of the Simulation Tool for Airflow in the human Nose (STAN), developed at the Darmstadt University of technology in cooperation with the University Hospital in Greifswald, is to use these techniques to support the rhinosurgeon in diagnosis and planning of therapy (Frühauf T, Mlynski G. Simulation and visualization of the air flow in the human nose. Proceedings of the First World Congress on Computational Medicine, Austin, Texas, 1994). A system has been developed that realizes a three-dimensional (3D) reconstruction of the endonasal cavities based on computer tomography (CT) scans. This semiautomatic reconstruction method requires minimal manual intervention. The surface model is used to create an unstructured 3D volume mesh suitable for finite volume simulations. In this way, an individual simulation based on patient-specific data can be realized. At the University Hospital in Greifswald, experimental investigations and measurements are made in nasal models to verify the simulation result. The goal of this project is to investigate individual nasal complaints and to detect respiratory disorders. The surgeon should be able to simulate the disordered respiration before performing a surgical procedure, and thereby increase the effectiveness of surgical planning. Comp Aid Surg 5:175–179 (2000). © 2000 Wiley-Liss, Inc.

关键词： biomechanical simulation computer-aided diagnosis computational biofluids rhinosurgery

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A case study on human upper limb modelling for dynamic simulation

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computer Methods in Biomechanics and Biomedical Engineering 1999年第1期2卷 65-82页

作者： Maurel, Walter Thalmann, Daniel Computer Graphics Lab - Swiss Federal Institute of Technology LIG/DI/EPFL CH 1015 Lausanne Switzerland

Modelling consists of developing a representation of the properties of an object or a phenomenon with respect to the goals of its analysis. In this paper, the procedure presented is that followed in the CHARM project for human upper limb modelling with respect to the project constraints on the model implementation and simulation. The objective is to develop a Comprehensive Human Animation Resource Model allowing the simulation of human motion, including the finite element simulation of soft tissue deformation and muscular contraction. Generally, models are presented based on assumptions left for a fortiori validation. The a priori considerations which lead to these assumptions are rarely detailed. Here, the aim is to form a basis for the choices and assumptions which are to be made prior to the validation. The analysis is based on the general approach for the modelling of multi-body deformable systems as well as on previous studies on the human upper limb. © 1998 OPA (Overseas Publishers Association) N.V.

关键词： Deformation

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Nonverbal communication interface for collaborative virtual environments

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Virtual Reality 1999年第1期4卷 49-59页

作者： Guye-Vuillème, A. Capin, T.K. Pandzic, I.S. Magnenat Thalmann, N. Thalmann, D. Computer Graphics Laboratory Swiss Federal Institute of Technology Lausanne Switzerland MIRALAB-CUI University of Geneva Switzerland Computer Graphics Laboratory Swiss Federal Institute of Technology CH1015 Lausanne Switzerland

Nonverbal communication is an important aspect of real-life face-to-face interaction and one of the most efficient ways to convey emotions, therefore users should be provided the means to replicate it in the virtual world. Because articulated embodiments are well suited to provide body communication in virtual environments, this paper first reviews some of the advantages and disadvantages of complex embodiments. After a brief introduction to nonverbal communication theories, we present our solution, taking into account the practical limitations of input devices and social science aspects. We introduce our sample of actions and implementation using our VLNET (Virtual Life Network) networked virtual environment and discuss the results of an informal evaluation experiment. © Springer-Verla London Ltd.

关键词： Embodiments Emotional feedback Networked virtual environments Nonverbal communication Social interaction in virtual environments

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Virtual human life simulation and database: Why and how

Virtual human life simulation and database: Why and how

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1999 International Symposium on Database Applications in Non-Traditional Environments, DANTE 1999

作者： Thalmann, Daniel Parenc, Nathalie Boulic, Ronan Computer Graphics Laboratory Swiss Federal Institute of Technology Lausanne Switzerland

ISBN: (纸本)0769504965

In combination with the rapid technical improvements of computers, building large virtual scenes has become a popular field in computer graphics. Often, within a real reconstructed city, a building that has disappeared, or a virtual town, virtual humans populating these scenes are expected to provide a feeling of real life. Our specific aim is to populate these scenes with virtual humans in order to offer assistance in decision making concerning urban infrastructures. In this view, we have to integrate the problem of planning human actions and behaviour for urban life simulation into a virtual town. We present an informed environment, which corresponds to a database dedicated to urban life simulation. We discuss the use of a database, and methods and tools for creating and providing the information necessary for animating virtual humans in a city. The informed environment is based on the hierarchical decomposition of an urban scene into environment entities providing geometrical information as well as semantic notions, thus allowing a more realistic simulation of humans. In this manner, virtual humans can be provided with a certain kind of urban knowledge. Moreover, the database can offer other types of services for scene creation for example. © 2000 IEEE.

关键词： Database systems

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Building a hybrid tracking system: Integration of optical and magnetic tracking 2

Building a hybrid tracking system: Integration of optical an...

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2nd IEEE and ACM International Workshop on Augmented Reality, IWAR 1999

作者： Auer, T. Pinz, A. Computer Graphics and Vision Graz University of Technology Inffeldgasse 16 Graz8010 Austria

ISBN: (纸本)0769503594

Multi-user augmented reality systems require excellent registration in order to allow cooperation among the users. In order to satisfy this need we have built a hybrid tracking system integrating magnetic and optical tracking. Prediction from the magnetic tracker allows for rather small search areas in the optical tracking subsystem. Our hybrid tracking system is faster than a standalone optical tracking system and outperforms a magnetic system in terms of accuracy and jitter. © 1999 IEEE.

关键词： Augmented reality

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Weight-codings in a genetic algorithm for the multi-constraint knapsack problem

Weight-codings in a genetic algorithm for the multi-constrai...

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1999 Congress on Evolutionary Computation, CEC 1999

作者： Raidl, Gunther R. Institute of Computer Graphics Vienna University of Technology Karlsplatz 13/1861 1040 Vienna Austria

ISBN: (纸本)0780355369

This paper presents different variants of weight-coding in a genetic algorithm (GA) for solving the multi-constraint knapsack problem (MKP). In this coding, a chromosome is a vector of weights associated with the items of the MKP. The phenotype is obtained by using the weights to generate a modified version of the original problem and applying a decoding heuristic to it. Four techniques of biasing the original problem with weights are discussed. Two well working decoding heuristics, one based on surrogate relaxation and the other based on Lagrangian relaxation, are introduced. The different weight-coding variants are experimentally compared to each other using a steady-state GA. Furthermore, the influence of the biasing strength, a strategy parameter of the codings, is investigated. In general, the GA found solutions being substantially better than those obtained by applying heuristics to the MKP directly. © 1999 IEEE.

关键词： Genetic algorithms

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A seamless shape for HANIM compliant bodies 4

A seamless shape for HANIM compliant bodies

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4th Symposium on Virtual Reality Modeling Language, VRML 1999

作者： Babski, Christian Thalmann, Daniel Computer Graphics Laboratory Swiss Federal Institute Of Technology LausanneCH1015 Switzerland

ISBN: (纸本)1581130791

A standard for representing avatars in VRML worlds has been specified by the Humanoid Animation (HANIM) working group. Avatars based on these specifications are generally composed of a set of body surfaces, which do not ensure satisfying continuity between connected body parts. This paper proposes a generic method for performing real-time body deformations using JAVA and VRML. This method allows generating seamless bodies fully compatible with HANIM standard. CR Categories and Subject Descriptors: 1.3.5 [computer graphics]: Computational Geometry and Object Modeling-surface representations, 1.3.7 [computer graphics]: ThreeDimensional graphics and Realism-Virtual reality. © 1999 ACM.

关键词： Deformation

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Level of autonomy for virtual human agents 5th

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5th European Conference on Artificial Life, ECAL 1999

作者： Musse, Soraia Raupp Kallmann, Marcelo Thalmann, Daniel Computer Graphics Lab Swiss Federal Institute of Technology EPFL DI-LIG LausanneCH 1015 Switzerland

ISBN: (纸本)3540664521

This paper proposes a paradigm for specification of virtual human agents’ level of autonomy. The idea we present in this paper aims at optimi sing the required complexity of agents in order to perform realistic simulations. The paradigm is based on the distribution of the required virtual human agent "intelligence" to other simulation entities like groups of agents, and objects. © Springer-Verlag Berlin Heidelberg 1999.

关键词： Autonomous agents

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Adaptive parameterization for reconstruction of 3D freeform objects from laser-scanned data 7

Adaptive parameterization for reconstruction of 3D freeform ...

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7th Pacific Conference on computer graphics and Applications, Pacific graphics 1999

作者： Fischer, A. Manor, A. Barhak, Y. CMSR Laboratory for Computer Graphics and CAD Department of Mechanical Engineering Technion - Israel Institute of Technology Haifa32000 Israel

ISBN: (纸本)0769502938

This paper proposes a new adaptive parametrization method to overcome the problems of using laser scanners in Reverse Engineering. The method is based on the following stages: (a) Detecting a 3D boundary of the parametric base surface by matching an intensity image from a CCD camera with the scanned data. (b) Adaptively reconstructing a parametric base surface with a non-self intersecting grid, based on a PDE method (c) Calculating the parametrization of the 3D sampled points. (d) Fitting the surface by applying a least square (LSQ) approximation method with boundary constraints. The feasibility of the parametrization algorithm is demonstrated on several examples using sculptured free objects. © 1999 IEEE.

关键词： Reverse engineering

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Real-time maximum intensity projection

Real-time maximum intensity projection

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1st Joint Eurographics - IEEE TCVG Symposium on Visualization, VisSym 1999

作者： Mroz, Lukas König, Andreas Gröller, Eduard Vienna University of Technology Institute of Computer Graphics Karlsplatz 13/186/2 ViennaA-1040 Austria

ISBN: (纸本)9783709168035

Maximum Intensity Projection (MIP) is a volume rendering technique which is used to extract high-intensity structures from volumetric data. At each pixel the highest data value encountered along the corresponding viewing ray is determined. MIP is commonly used to extract vascular structures from medical MRI data sets (angiography). The usual way to compensate for the loss of spatial and occlusion information in MIP images is to view the data from different view points by rotating them. As the generation of MIP is usually non-interactive, this is done by calculating multiple images offline and playing them back as an animation. In this paper a new algorithm is proposed which is capable of interactively generating Maximum Intensity Projection images using parallel projection and templates. Voxels of the data set which will never contribute to a MIP due to their neighborhood are removed during a preprocessing step. The remaining voxels are stored in a way which guarantees optimal cache coherency regardless of the viewing direction. For use on low-end hardware, a preview-mode is included which renders only more significant parts of the volume during user interaction. Furthermore we demonstrate the usability of our data structure for extensions of the MIP technique like MIP with depth-shading and Local Maximum Intensity Projection (LMIP). © 1999 Eurographics Association. All rights reserved.

关键词： Angiography

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