Journal Article Evaluation of a Mobile Projector-Based Indoor Navigation Interface Get access Ming Li, Ming Li * 1Computer Graphics Group, RWTH Aachen University, Aachen, Germany *Corresponding author: [email protected] Search for other works by this author on: Oxford Academic Google Scholar Katrin Arning, Katrin Arning 2Human Computer Interaction Center, RWTH Aachen University, Aachen, Germany Search for other works by this author on: Oxford Academic Google Scholar Oliver Sack, Oliver Sack 2Human Computer Interaction Center, RWTH Aachen University, Aachen, Germany Search for other works by this author on: Oxford Academic Google Scholar Jiyoung Park, Jiyoung Park 3Ewha Womans University, Seoul, Korea Search for other works by this author on: Oxford Academic Google Scholar Myoung-Hee Kim, Myoung-Hee Kim 3Ewha Womans University, Seoul, Korea Search for other works by this author on: Oxford Academic Google Scholar Martina Ziefle, Martina Ziefle 2Human Computer Interaction Center, RWTH Aachen University, Aachen, Germany Search for other works by this author on: Oxford Academic Google Scholar Leif Kobbelt Leif Kobbelt 1Computer Graphics Group, RWTH Aachen University, Aachen, Germany Search for other works by this author on: Oxford Academic Google Scholar Interacting with Computers, Volume 26, Issue 6, November 2014, Pages 595–613, https://doi.org/10.1093/iwc/iwt053 Published: 06 November 2013 Article history Received: 12 January 2013 Revision received: 09 September 2013 Accepted: 16 September 2013 Published: 06 November 2013

We present a novel low-cost method for visual communication and telepresence in a CAVE -like environment, relying on 2D stereo-based video avatars. The system combines a selection of proven efficient algorithms and approximations in a unique way, resulting in a convincing stereoscopic real-time representation of a remote user acquired in a spatially immersive display. The system was designed to extend existing projection systems with acquisition capabilities requiring minimal hardware modifications and cost. The system uses infrared-based image segmentation to enable concurrent acquisition and projection in an immersive environment without a static background. The system consists of two color cameras and two additional b/w cameras used for segmentation in the near-IR spectrum. There is no need for special optics as the mask and color image are merged using image-warping based on a depth estimation. The resulting stereo image stream is compressed, streamed across a network, and displayed as a frame-sequential stereo texture on a billboard in the remote virtual environment.

This paper presents a multi-resolutional surface deformable model with physical property adjustment scheme and shape-preserving springs to represent surface-deformable objects efficiently and robustly. In order to reduce the computational complexity while ensuring the same global volumetric behaviour for the deformable object, we introduce a multi-resolutional mass-spring model that is locally refined using the modified-butterfly subdivision scheme. For robust deformation, a shape-preserving spring, which helps to restore the model to the original shape, is proposed to reduce the animation instability. Volume and shape preservation is indirectly achieved by restoring the model to the original shape without computing the actual volume and associated forces at every iteration. Most existing methods concentrate on visual realism of multi-resolutional deformation and often neglect to maintain the dynamic behavioural integrity between detail levels. In order to preserve overall physical behaviour, we present a new scheme for adjusting physical properties between different levels of details. During the animation of deformable objects, the part of the object under external forces beyond a threshold or with large surface curvature variations is refined with a higher level of detail. The physical properties of nodes and springs in the locally refined area are adjusted in order to preserve the total mass and global behaviour of the object. The adequacy of the proposed scheme was analysed with tests using practical mesh examples. Experimental results demonstrate improved efficiency in object deformation and preservation of overall behaviour between different levels. Copyright © 2005 John Wiley & Sons, Ltd.

We present an application for design and simulation of a building that fits into its surroundings in a heterogeneous collaborative virtual environment. Constructed heterogeneous collaborative VE consists of different VR display systems such as a virtual table and a projection wall. Since the virtual table provides a table-type workspace on a horizontal screen, it is efficient for interactive design of a building with a bird's-eye-view. However, it is not so efficient to view a designed building in the same proportions as that for a real building. On the other hand, as the projection wall is a vertical type VR environment having a large display, it enables simulation of the whole design process on a virtual table in frontal view. In addition, it also enables navigation around the building and in its surroundings. So we propose to use a projection wall as well as virtual table for constructing virtual environment so that design and simulation could be performed at the same time in each environment. Since the two VR systems are located close to one another, the user in the projection wall can participate in the design process that is performed in the virtual table indirectly through verbal communication. Guided 3D interaction techniques are also described for designing a building with ease in the 3D VR environment.

Abstract We present a time‐varying deformable model to visualize and analyze the motion of the left ventricle from a time series of 3‐D images. The model is composed of a non‐rigid body that deforms around a reference shape obtained from the previous time step. At each time step, the position and orientation of the left ventricle are extracted from the feature points of images. This information gives the position and orientation of the coordinate system attached to the non‐rigid body. To compute a dense non‐rigid motion field over the entire endocardial wall of the left ventricle, we introduce a 3‐D blob finite element and Galerkin interpolants based on 3‐D Gaussian, and use a physically based finite element method and a modal analysis. Then, cinematic attributes are visualized in pseudo colors on the reconstructed surface in order to help medical doctors in their interpretation of the data. Using the presented model, we estimate clinically useful quantitative parameters such as regional wall motion and ejection fraction. Experimental results are shown in a time series of X‐ray angiographic images. Copyright ©2001 John Wiley & Sons, Ltd.

Deformable surface models are an attractive method for segmenting the three-dimensional shapes of complex anatomic structures in volumetric medical images. Despite the success of this approach, several problems remain. In this paper, we propose a multiscale deformable surface model with non-intersection constraint forces that successfully addresses three significant problems-sensitivity to model initialization, difficulties in dealing with severe object concavities, and model self-intersection. The first two problems are addressed by the multiscale scheme, which progressively resamples the triangulated, deformable surface model both globally and locally, matching its resolution to the levels of a volume image pyramid. We address the third problem by including a non-intersection constraint force among the customary internal and external forces in the physics-based formulation. We apply our new deformable surface model to the challenging task of extracting brain cortical surfaces.

A number of segmentation algorithms have been developed, but those algorithms are not effective on volume reconstruction because they are limited to operating only on two-dimensional (2-D) images. In this paper, we propose the volumetric object reconstruction method using the three-dimensional Markov random field (3D-MRF) model-based segmentation. The 3D-MRF model is known to be one of efficient ways to model spatial contextual information. The method is compared with the 2-D region growing scheme under three types of interpolation. The results show that the proposed method is better in the aspect of image quality than other methods.