5.2008, 1

Presence in a Three-Dimensional Test Environment: Benefit or Threat to Market Research?

Alma Berneburg

In market research, the adoption of interactive virtual reality-techniques could be expected to contain many advantages: artificial lab environments could be designed in a more realistic manner and the consideration of “time to the market”-factors could be improved. On the other hand, with an increasing degree of presence and the notional attendance in a simulated test environment, the market research task could fall prey to the tensing virtual reality adventure.

In the following study a 3D-technique is empirically tested for its usability in market research. It will be shown that the interactive 3D-simulation is not biased by the immersion it generates and provides considerably better test results than 2D-stimuli do.

[Submitted: April 3rd, 2007 | In Peer-Review: April 11th, 2007 | Resubmitted: October 10th, 2007 | Accepted: September 12th, 2007 | Published: June 13th, 2008 ]

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5.2008, 2

Rendering Falling Leaves on Graphics Hardware

GRAPP 2007 Special Issue

Pere-Pau Vázquez et al.

There is a growing interest in simulating natural phenomena in computer graphics applications. Animating natural scenes in real time is one of the most challenging problems due to the inherent complexity of their structure, formed by millions of geometric entities, and the interactions that happen within. An example of natural scenario that is needed for games or simulation programs are forests. Forests are difficult to render because the huge amount of geometric entities and the large amount of detail to be represented. Moreover, the interactions between the objects (grass, leaves) and external forces such as wind are complex to model. In this paper we concentrate in the rendering of falling leaves at low cost. We present a technique that exploits graphics hardware in order to render thousands of leaves with different falling paths in real time and low memory requirements.

[Submitted: May 31st, 2007 | In Peer-Review: June 6th, 2007 | Resubmitted: October 25th, 2007 | Accepted: September 12th, 2007 | Published: April 15th, 2008 ]

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5.2008, 3

Adaptive Cube Tessellation for Topologically Correct Isosurfaces

GRAPP 2007 Special Issue

Francisco Velasco et al.

Three dimensional datasets representing scalar fields are frequently rendered using isosurfaces. For datasets arranged as a cubic lattice, the marching cubes algorithm is the most used isosurface extraction method. However, the marching cubes algorithm produces some ambiguities which have been solved using different approaches that normally imply a more complex process. One of them is to tessellate the cubes into tetrahedra, and by using a similar method (marching tetrahedra), to build the isosurface. The main drawback of other tessellations is that they do not produce the same isosurface topologies as those generated by improved marching cubes algorithms. We propose an adaptive tessellation that, being independent of the isovalue, preserves the topology. Moreover the tessellationallows the isosurface to evolve continuously when the isovalue is changed continuously.

[Submitted: May 7th, 2007 | In Peer-Review: May 8th, 2007 | Resubmitted: September 25th, 2007 | Accepted: September 12th, 2007 | Published: April 28th, 2008 ]

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5.2008, 4

RFIDice - Augmenting Tabletop Dice with RFID

PerGames 2007 Special Issue

Steve Hinske et al.

Augmented dice allow players of tabletop games to have the result of a roll be automatically recorded by a computer, e.g., for supporting strategy games. We have built a set of three augmented-dice-prototypes based on radio frequency identification (RFID) technology, which allows us to build robust, cheap, and small augmented dice. Using a corresponding readout infrastructure and a sample application, we have evaluated our approach and show its advantages over other dice augmentation methods discussed in the literature.

[Submitted: August 16th, 2007 | In Peer-Review: August 23rd, 2007 | Resubmitted: February 11th, 2008 | Accepted: December 3rd, 2008 | Published: August 5th, 2008 ]

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5.2008, 5

Multi-Mode Tensor Representation of Motion Data

GRAPP 2007 Special Issue

Björn Krüger et al.

In this paper, we investigate how a multilinear model can be used to represent human motion data. Based on technical modes (referring to degrees of freedom and number of frames) and natural modes that typically appear in the context of a motion capture session (referring to actor, style, and repetition), the motion data is encoded in form of a high-order tensor. This tensor is then reduced by using N-mode singular value decomposition. Our experiments show that the reduced model approximates the original motion better then previously introduced PCA-based approaches. Furthermore, we discuss how the tensor representation may be used as a valuable tool for the synthesis of new motions.

[Submitted: May 7th, 2007 | In Peer-Review: May 8th, 2008 | Resubmitted: February 6th, 2008 | Accepted: January 16th, 2008 | Published: August 5th, 2008 ]

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5.2008, 6

Predictive-DCT Coding for 3D Mesh Sequences Compression

GRAPP 2007 Special Issue

Rachida Amjoun et al.

This paper proposes a new compression algorithm for dynamic 3d meshes. In such a sequence of meshes, neighboring vertices have a strong tendency to behave similarly and the degree of dependencies between their locations in two successive frames is very large which can be efficiently exploited using a combination of Predictive and DCT coders (PDCT). Our strategy gathers mesh vertices of similar motions into clusters, establish a local coordinate frame (LCF) for each cluster and encodes frame by frame and each cluster separately. The vertices of each cluster have small variation over a time relative to the LCF. Therefore, the location of each new vertex is well predicted from its location in the previous frame relative to the LCF of its cluster. The difference between the original and the predicted local coordinates are then transformed into frequency domain using DCT. The resulting DCT coefficients are quantized and compressed with entropy coding. The original sequence of meshes can be reconstructed from only a few non-zero DCT coefficients without significant loss in visual quality. Experimental results show that our strategy outperforms or comes close to other coders.

[Submitted: May 31st, 2007 | In Peer-Review: June 6th, 2007 | Resubmitted: April 8th, 2008 | Accepted: October 10th, 2007 | Published: September 30th, 2008 ]

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5.2008, 7

Multi-Contact Grasp Interaction for Virtual Environments

GI VR/AR Special 2007

Daniel Holz et al.

The grasping of virtual objects has been an active research field for several years. Solutions providing realistic grasping rely on special hardware or require time-consuming parameterizations. Therefore, we introduce a flexible grasping algorithm enabling grasping without computational complex physics. Objects can be grasped and manipulated with multiple fingers. In addition, multiple objects can be manipulated simultaneously with our approach. Through the usage of contact sensors the technique is easily configurable and versatile enough to be used in different scenarios.

[Submitted: August 20th, 2007| In Peer-Review: August 23rd, 2007 | Resubmitted: February 29th, 2008 | Accepted: January 16th, 2008 | Published: August 21st, 2008 ]

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5.2008, 8

The TViews Table Role-Playing Game

PerGames 2007 Special Issue

Ali Mazalek et al.

The TViews Table Role-Playing Game (TTRPG) is a digital tabletop role-playing game that runs on the TViews table, bridging the separate worlds of traditional role-playing games with the growing area of massively multiplayer online role-playing games. The TViews table is an interactive tabletop media platform that can track the location of multiple tagged objects in real-time as they are moved around its surface, providing a simultaneous and coincident graphical display. In this paper we present the implementation of the first version of TTRPG, with a content set based on the traditional Dungeons & Dragons rule-set. We also discuss the results of a user study that used TTRPG to explore the possible social context of digital tabletop role-playing games.

[Submitted: August 21st, 2007 | In Peer-Review: August 23rd, 2007 | Resubmitted: March 23rd, 2008 | Accepted: January 21st, 2008 | Published: August 12th, 2008 ]

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5.2008, 9

A Physically Based Transmission Model of Rough Surfaces

GRAPP 2007 Special Issue

Huiying Xu et al.

Transparent and translucent objects involve both light reflection and transmission at surfaces. This paper presents a physically based transmission model of rough surface. The surface is assumed to be locally smooth, and statistical techniques is applied to calculate light transmission through a local illumination area. We have obtained an analytical expression for single scattering. The analytical model has been compared to our Monte Carlo simulations as well as to the previous simulations, and good agreements have been achieved. The presented model has potential applications for realistic rendering of transparent and translucent objects.

[Submitted: April 22nd, 2007 | In Peer-Review: April 25th, 2007 | Resubmitted: May 13th, 2008 | Accepted: February 2nd, 2008 | Published: November 13th, 2008 ]

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5.2008, 10

Gesture-Based, Touch-Free Multi-User Gaming on Wall-Sized, High-Resolution Tiled Displays

PerGames 2007 Special Issue

Daniel Stødle et al.

Having to carry input devices can be inconvenient when interacting with wall-sized, high-resolution tiled displays. Such displays are typically driven by a cluster of computers. Running existing games on a cluster is non-trivial, and the performance attained using software solutions like Chromium is not good enough.

This paper presents a touch-free, multi-user, human-computer interface for wall-sized displays that enables completely device-free interaction. The interface is built using 16 cameras and a cluster of computers, and is integrated with the games Quake 3 Arena (Q3A) and Homeworld. The two games were parallelized using two different approaches in order to run on a 7x4 tile, 21 megapixel display wall with good performance.

The touch-free interface enables interaction with a latency of 116 ms, where 81 ms are due to the camera hardware. The rendering performance of the games is compared to their sequential counterparts running on the display wall using Chromium. Parallel Q3A's framerate is an order of magnitude higher compared to using Chromium. The parallel version of Homeworld performed on par with the sequential, which did not run at all using Chromium. Informal use of the touch-free interface indicates that it works better for controlling Q3A than Homeworld.

[Submitted: July 26th, 2007 | In Peer-Review: August 16th, 2008 | Resubmitted: April 21st, 2008 | Accepted: March 11th, 2008 | Published: November 14th, 2008 ]

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