GRAPP 2017 Abstracts

Area 1 - Geometry and Modeling
Full Papers Short Papers
Area 2 - Rendering
Full Papers Short Papers
Area 3 - Animation and Simulation
Full Papers Short Papers
Area 4 - Interactive Environments
Full Papers Short Papers

Area 1 - Geometry and Modeling

Full Papers
Paper Nr: 10
Title:

Persistence-based Interest Point Detection for 3D Deformable Surface
Authors:

Xupeng Wang, Ferdous Sohel, Mohammed Bennamoun, Yulan Guo and Hang Lei
Abstract: Several approaches for interest point detection on rigid shapes have been proposed, but few are available for non-rigid shapes. It is a very challenging task due to the presence of the large degrees of local deformations. This paper presents a novel method called persistence-based heat kernel signature (pHKS). It consists of two steps: scalar field construction and interest point detection. We propose to use the heat kernel signature function at a moderately small time scale to construct the scalar field. It has the advantage of being stable under various transformations. Based on the predefined scalar field, a 0-dimensional persistence diagram is computed, and the local geometric and global structural information of the shape are captured at the same time. Points with local maxima and high persistence are selected as interest points. We perform a comprehensive evaluation on two popular datasets (i.e., PHOTOMESH and Interest Points Dataset) to show the effectiveness of our method. Compared with existing techniques, our interest point detector achieves a superior performance in terms of repeatability and distinctiveness.
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Paper Nr: 14
Title:

A Three-dimensional Error-diffusion Algorithm for Importance Sampling with Blue-noise Property
Authors:

Ke Wang, Jiaojiao Zhao, Jie Feng and Bingfeng Zhou
Abstract: We propose a novel discrete three-dimensional sampling algorithm based on the error-diffusion method, which can generate sampling points with blue-noise property. To obtain sampling points with a high quality blue-noise spectrum in 3D domain, we introduce an effective metric for the 3D blue-noise property based on 3D Fourier transform. Then, a cost function used for the search of optimal parameters, including optimal diffusion coefficients and threshold modulation strength values, is designed to guarantee the blue-noise property of sampling points. Experiments show that our algorithm is able to generate sampling points with uniform and random distribution, which possess 3D blue-noise property, and supports importance sampling in three dimensional domain. Comparing with similar work, our algorithm can achieve sampling point distribution that possesses better isotropic properties and has lower time cost in 3D discrete domain. Several applications including volume rendering and tetrahedral meshing are also explored.
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Paper Nr: 17
Title:

Extensible Multi-domain Generation of Virtual Worlds using Blackboards
Authors:

Gaetan Deglorie, Rian Goossens, Sofie Van Hoecke and Peter Lambert
Abstract: Procedural generation of large virtual worlds remains a challenge, because current procedural methods mainly focus on generating assets for a single content domain, such as height maps, trees or buildings. Furthermore current approaches for multi-domain content generation, i.e. generating complete virtual environments, are often too ad-hoc to allow for varying design constraints from creatives industries such as the development of video games. In this paper, we propose a multi-domain procedural generation method that uses modularized, single-domain generation methods that interact on the data level while operating independently. Our method uses a blackboard architecture specialized to fit the needs of procedural content generation. We show that our approach is extensible to a wide range of use cases of virtual world generation and that manual or procedural editing of the generated content of one generator is automatically communicated to the other generators, which ensures a consistent and coherent virtual world. Furthermore, the blackboard approach automatically reasons about the generation process which allows 52% to 98% of the activations, i.e. executions of the single-domain content generators, to be discarded without compromising the generated content, resulting in better performing large world generation.
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Paper Nr: 20
Title:

Quality Enhancement Techniques for Building Models Derived from Sparse Point Clouds
Authors:

Steffen Goebbels and Regina Pohle-Fröhlich
Abstract: This paper describes processing steps that improve both geometric consistency and appearance of CityGML models. In addition to footprints from cadastral data and sparse point clouds obtained from airborne laser scanning, we use true orthophotos to better detect and model edges. Also, procedures to heal self-intersection of polygons and non-planarity of roof facets are presented. Additionally, the paper describes an algorithm to cut off invisible parts of walls. We incorporate these processing steps into our data based framework for building model generation from sparse point clouds. Results are presented for German cities of Krefeld and Leverkusen.
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Paper Nr: 48
Title:

A Pipeline and Metric for Validation of Personalized Human Body Models
Authors:

Sukhraj Singh and Subodh Kumar
Abstract: Advanced and personalized Human Body Models (HBM) are increasingly important in human centered industry design such as passive vehicular safety analysis, using finite element and other methods. Often accurate HBMs are painstakingly constructed for median human dimensions, and then modified and re-sized using personalization algorithms for various applications. Personalization algorithms rely on various anthropometric measurements, and sometimes manual intervention, to deform the median HBM. The quality of a personalized model is often defined in terms of local properties such as aspect ratio of finite elements produced. In some cases it is inferred by visual comparison with some ground truth model or by measuring the anthropometric errors with respect to known values. We seek to define the quality of deformation in anatomically suitable geometric terms, which can be automatically computed. To this end, we compare the deformed anatomical surface meshes with that of the median mesh in a shape descriptor space. Shape comparison and matching is a well studied area. The tools devised for the same are largely application dependent. We present pipeline and a metric for validating anatomical surface meshes. It is a problem that has not been extensively studied, even though general shape comparison and matching techniques abound. Our metric incorporates global and part based shape signatures. The main contribution of our work is to explore techniques suitable for comparison of anatomical meshes by non technical experts. We formulate a pipeline that needs minimal user intervention.
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Short Papers
Paper Nr: 13
Title:

An Efficient Geometric Algorithm for Clipping and Capping Solid Triangle Meshes
Authors:

Aaron Scherzinger, Tobias Brix and Klaus H. Hinrichs
Abstract: Clipping three-dimensional geometry by arbitrarily oriented planes is a common operation in computer graphics and visualization applications. In most cases, the geometry used in those applications is provided as surface models consisting of triangles which are called meshes. Clipping such surface models by a plane cuts them open, destroying the illusion of a solid object. Often this is not desirable, and the resulting mesh should again be a closed surface model, e.g., when generating cross-sections in technical visualization applications. We propose an algorithm which performs the clipping operation geometrically for a given input mesh on the GPU. The intersection edges of the mesh and the clipping plane are then transferred to the CPU, where a cap geometry closing the mesh is computed and eventually added to the clipped mesh. Our algorithm can process solid (i.e., closed two-manifold) triangle meshes, or sets of non-intersecting solids, and has a worst-case runtime of O(N + n log n) where N is the number of triangles in the input geometry, and n is the number of input triangles intersecting the clipping plane.
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Paper Nr: 19
Title:

Calculation of Optimal Luminaires for Architectural Design
Authors:

Rodrigo Leira, Eduardo Fernández and Gonzalo Besuievsky
Abstract: The selection and location of optimal luminaries is a central aspect of architectural design. Its complexity arises due to the diversity of existing luminaires, and the problems related to the need of achieving a set of lighting goals and constraints. The use of computer simulation software can bring an improved support in decision making at design time. CAD applications for illumination assessment are generally based on a working forward strategy, where the designer selects all the design elements, in order to calculate the resulting illumination. In this paper we present an inverse approach for the selection of luminaires, where the designer defines a set of lighting intentions to satisfy, and then an optimization algorithm iterates, converging to a feasible and optimal solution. The method allows to use a database consisting of hundreds of luminaires and a set of possible locations. In each iteration, after the first reflection of a potential configuration is calculated, the radiosity method is used to compute the final illumination of the scene.
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Paper Nr: 23
Title:

Rate-Distortion Optimized Wavelet-based Irregular Mesh Coding
Authors:

Jonas El Sayeh Khalil, Adrian Munteanu and Peter Lambert
Abstract: This work investigates the optimization of mesh quality at lossy rates for a lossless scalable wavelet-based irregular mesh codec. Whereas previously proposed wavelet-based irregular mesh codecs offer coarse-grain resolution scalability, in this paper we propose a coding scheme which enables fine-grain quality scalability. This is done by avoiding the use of geometric data in the encoding process, which reduces dependencies within the data stream and allows for an unrestricted storage and transmission order of wavelet subband bitplanes and connectivity information. This in turn allows us to perform rate-distortion optimization, whereby the subband bitplanes to be encoded are determined by minimizing distortion subject to an overall target bitrate. Experimental results show that the proposed coding approach offers fine-grain quality scalability, achieves optimality in rate-distortion sense and improves compression performance over the state of the art.
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Paper Nr: 28
Title:

Riemannian Filters for Multi-variate Mesh Signals
Authors:

Teodor Cioaca, Bogdan Dumitrescu and Mihai Sorin Stupariu
Abstract: Designing filters over irregular non-Euclidean domains requires algorithms that take into account the intrinsic curvature of these domains. We propose a new filtering method based on Riemannian weighted averages. The resulting filters are non-Euclidean adaptations of the mean shift and blurring mean shift algorithms. We also introduce a hybrid, efficient computing strategy by combining these iterative filtering methods with wavelet multi-resolution editing. The applications of our filters include multi-variate mesh data smoothing, denoising, attribute enhancement and curvature filtering.
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Paper Nr: 53
Title:

Modeling Semantics for Building Deconstruction
Authors:

Enrico Marino, Federico Spini, Alberto Paoluzzi, Danilo Salvati, Christian Vadalà, Antonio Bottaro and Michele Vicentino
Abstract: In this paper we discuss the motivation, the technology, the design and the use-model of a novel web service for quantity surveyors, aiming to exploit virtual and augmented reality methods to implement a “zero waste” model, i.e. a new design paradigm where the waste materials from demolition become resources for reconstruction. The goal of this project is to provide virtual/augmented reality tools through quick modeling of buildings and their fast augmentation with semantic content.
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Paper Nr: 60
Title:

Initial Results of a Method for the Generation of Triangle Meshes Representing Bone Fragments using a Spatial Decomposition
Authors:

Félix Paulano-Godino and Juan J. Jiménez-Delgado
Abstract: The generation of a virtual representation of the bones and fragments is an artificial step required in order to obtain helpful models to work with in a simulation. Nowadays, the Marching Cubes algorithm is a de facto standard for the generation of geometric models from medical images. However, bone fragments models generated by Marching Cubes are huge and contain many unconnected geometric elements inside the bone due to the trabecular tissue. The development of new methods to generate geometrically simple 3D models from CT image stacks that preserve the original information extracted from them would be of great interest. In order to achieve that, a preliminary study for the development of a new method to generate triangle meshes from segmented medical images is presented. The method does not modify the points extracted from CT images, and avoid generating triangles inside the bone. The aim of this initial study is to analyse if a spatial decomposition may help in the process of generating a triangle mesh by using a divide-and-conquer approach. The method is under development and therefore this paper only presents some initial results and exposes the detected issues to be improved.
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Paper Nr: 1
Title:

A Simple and Correct Even-Odd Algorithm for the Point-in-Polygon Problem for Complex Polygons
Authors:

Michael Galetzka and Patrick Glauner
Abstract: Determining if a point is in a polygon or not is used by a lot of applications in computer graphics, computer games and geoinformatics. Implementing this check is error-prone since there are many special cases to be considered. This holds true in particular for complex polygons whose edges intersect each other creating holes. In this paper we present a simple even-odd algorithm to solve this problem for complex polygons in linear time and prove its correctness for all possible points and polygons. We furthermore provide examples and implementation notes for this algorithm.
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Paper Nr: 36
Title:

Generative Animation in a Physics Engine using Motion Captures
Authors:

Brian Wilke and Sudhanshu K. Semwal
Abstract: Motion captures are an industry standard for producing high-quality, realistic animations. However, generating novel animations from motion captures remains a complex, non-trivial problem. Many techniques have been developed, including kinematics and manually solving the equations of motion. We present a new technique using a physics engine to generate novel animations. Motion captures are effectively simulated within a popular open-source physics engine, Bullet, and two generative techniques are applied. These generative techniques -- asymmetric scaling and under-controlling -- are shown to be simple and straight-forward. The techniques and methods were implemented in Python and C++, and show new promising avenues for generative animation using existing motion captures
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Paper Nr: 62
Title:

Search & Retrieval in CAD Databases - A User-centric State-of-the-Art Overview
Authors:

Christoph Schinko, Thomas Vosgien, Thorsten Prante, Tobias Schreck and Torsten Ullrich
Abstract: This article presents a state-of-the-art overview on shape, information and design retrieval systems in the context of CAD engineering. In contrast to existing surveys, we classify the different approaches from a CAD application user point of view. As a consequence, we focus on features of surveyed techniques such as: supported shape data types, handling of geometric invariances, support of metadata, supported query types, quality of retrieval results, and the availability of implementations.
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Paper Nr: 63
Title:

Verlet with Collisions for Mass Spring Model Simulations
Authors:

Maciej Kot and Hiroshi Nagahashi
Abstract: In this paper we study the problem of the interaction of soft bodies modeled with mass spring models (MSM) and static elements of the environment. We show that in such setup it is possible to couple standard time evolution of MSMs with collision responses in a way, that does not require complex processing for multi collision situations while successfully preventing object inter-penetration. Moreover we show how to achieve similar energy dissipation for models with different resolutions when the friction is present.
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Area 2 - Rendering

Full Papers
Paper Nr: 7
Title:

Light Field Rendering for Head Mounted Displays using Pixel Reprojection
Authors:

Anne Juhler Hansen, Jákup Klein and Martin Kraus
Abstract: Light field displays have advantages over traditional stereoscopic head mounted displays, for example, because they can overcome the vergence-accommodation conflict. However, rendering light fields can be a heavy task for computers due to the number of images that have to be rendered. Since much of the information of the different images is redundant, we use pixel reprojection from the corner cameras to compute the remaining images in the light field. We compare the reprojected images with directly rendered images in a user test. In most cases, the users were unable to distinguish the images. In extreme cases, the reprojection approach is not capable of creating the light field. We conclude that pixel reprojection is a feasible method for rendering light fields as far as quality of perspective and diffuse shading is concerned, but render time needs to be reduced to make the method practical.
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Paper Nr: 8
Title:

Adaptive Rendering based on Adaptive Order Selection
Authors:

Hongliang Yuan, Changwen Zheng, Quan Zheng and Yu Liu
Abstract: We propose a new adaptive sampling and reconstruction method based on a novel, adaptive order polynomial fitting which can preserve various high-frequency features in generated images and meanwhile mitigate the noise efficiently. Some auxiliary features have strong linear correlation with luminance intensity in the smooth regions of the image, but the relationship does not hold in the high-frequency regions. In order to handle these cases robustly, we approximate luminance intensity in the auxiliary feature space by constructing local polynomial functions with order varying adaptively. Firstly, we sample the image space uniformly. Then we decide the order of fitting with the least estimated mean squared error (MSE) for each pixel. Finally, we distribute additional ray samples to areas with higher estimated MSE if sampling budget remains. We demonstrate that our method makes significant improvement in terms of both numerical error and visual quality compared with the state-of-the-art.
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Paper Nr: 37
Title:

A Real–time Global Illumination Approach for High Resolution Reflective Shadow Maps in Open World Scenes
Authors:

Daniel Bischoff, Tobias Schwandt and Wolfgang Broll
Abstract: The complexity of offline and real–time rendering of global illumination effects is a vast field of research. Covering the complexity of dynamic open–world environments with changing light conditions and moving objects is challenging in real–time rendering. Especially the quality of light properties needs to be physically correct and sufficiently fast even if the light and environment conditions are changing. In this paper, we present a fast global illumination approach suitable to achieve indirect lighting using high–resolution reflective shadow maps in real time. Based on LightSkin, we present an enhancement applying bidirectional shadow maps to improve the quality of shadows and global illumination effects in open–world environments. A novel combination of accumulating virtual area lights from the reflective shadow map with an indirect light representation using LightSkin’s proxy light sources shows a significant improvement. In an urban scene typical for open–world environments, the proposed approach is up to approx. 12 times faster than the original LightSkin approach. This makes our novel approach suitable for high–quality indoor as well as outdoor global illumination.
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Paper Nr: 47
Title:

Fast Capture of Spectral Image Series
Authors:

Sebastian Merzbach, Michael Weinmann, Martin Rump and Reinhard Klein
Abstract: In recent years there has been an increasing interest in multispectral imaging hardware. Among many other applications is the color-correct reproduction of materials. In this paper, we aim at circumventing the limitations of most devices, namely extensive acquisition times for acceptable signal-to-noise-ratios. For this purpose we propose a novel approach to spectral imaging that combines high-quality RGB data and spatial filtering of extremely noisy and sparsely measured spectral information. The capability of handling noisy spectral data allows a dramatic reduction of overall exposure times. The speed-up we achieve allows for spectral imaging at practical acquisition times. We use the RGB images for constraining the reconstruction of dense spectral information from the filtered noisy spectral data. A further important contribution is the extension of a commonly used radiometric calibration method for determining the camera response in the lowest, noise-dominated range of pixel values. We apply our approach both to capturing single high-quality spectral images, as well as to the acquisition of image-based multispectral surface reflectance. Our results demonstrate that we are able to lower the acquisition times for such multispectral reflectance from several days to the few hours necessary for an RGB-based measurement.
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Short Papers
Paper Nr: 29
Title:

Efficient Ray Traversal of Constrained Delaunay Tetrahedralization
Authors:

Maxime Maria, Sébastien Horna and Lilian Aveneau
Abstract: Acceleration structures are mandatory for ray-tracing applications, allowing to cast a large number of rays per second. In 2008, Lagae and Dutr\'{e} have proposed to use Constrained Delaunay Tetrahedralization (CDT) as an acceleration structure for ray tracing. Our experiments show that their traversal algorithm is not suitable for GPU applications, mainly due to arithmetic errors. This article proposes a new CDT traversal algorithm. This new algorithm is more efficient than the previous ones: it uses less arithmetic operations; it does not add extra thread divergence since it uses a fixed number of operation; at last, it is robust with 32-bits floats, contrary to the previous traversal algorithms. Hence, it is the first method usable both on CPU and GPU.
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Paper Nr: 42
Title:

Interactive Appearance Manipulation of Fiber-based Materials
Authors:

Stefan Krumpen, Michael Weinmann and Reinhard Klein
Abstract: Achieving a visually appealing experience for the user interaction with photo-realistic digitized micro-fiber materials is a challenging task. While state-of-the-art high-quality fabric modeling techniques rely on complex micro-geometry representations that are computationally expensive and not well-suited for interactive rendering, previous interactive reflectance models reach a speed-up at the cost of discarding many of the effects of light exchange that significantly contribute to the appearance of fabric materials. In this paper, we present a novel, example-based technique for the interactive manipulation of micro-fiber materials based on bidirectional texture functions (BTFs) that allow considering fine details in the surface reflectance behavior. BTFs of the respective material sample are acquired for varying fiber orientations and combined to a single texture representation that encodes material appearance depending on the view and light conditions as well as the orientations of the fibers. This model can be efficiently evaluated depending on the user input which, as demonstrated by our results, allows a realistic simulation of the interaction with micro-fiber materials in real-time.
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Paper Nr: 56
Title:

Automatic View Finding for Drone Photography based on Image Aesthetic Evaluation
Authors:

Xiaoliang Xiong, Jie Feng and Bingfeng Zhou
Abstract: Consumer-level remotely controlled smart drones are usually equipped with high resolution cameras, which make them possible to become unmanned "flying camera". For this purpose, in this paper, we propose an automatic view finding scheme which can autonomously navigate a drone to an proper space position where a photo with an optimal composition can be taken. In this scheme, an automatic aesthetic evaluation for image composition is introduced to navigate the flying drone. It is accomplished by applying commonly used composition guidelines on the image transmitted from the drone at current view. The evaluation result is then conversely used to control the flight and provide feedback for the drone to determine its next movement. In flight control, we adopt a downhill simplex strategy to search for the optimal position and viewing direction of the drone in its flying space. When the searching converges, the drone stops and take an optimal image at current position.
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Paper Nr: 15
Title:

Coherent Ray-Space Hierarchy Via Ray Hashing and Sorting
Authors:

Nuno T. Reis, Vasco S. Costa and João M. Pereira
Abstract: We present an algorithm for creating an n-level Ray-Space Hierarchy (RSH) of coherent rays that runs on a GPU. Our algorithm uses a rasterization stage to process the primary rays, then inputs those results in the RSH stage which processes the secondary rays. The RSH algorithm generates bundles of rays, hashes them and sorts them. Thus we generate a ray list containing adjacent coherent rays to improve the rendering performance of the RSH vs a classical approach. Moreover, scene geometry is partitioned into a set of bounding spheres and, then, intersected with the RSH to further decrease the amount of false ray bundle-primitive intersection tests. We show that our technique notably reduces the amount of ray-primitive intersection tests, required to render an image. In particular it performs up to 50% better in this metric than other algorithms in this class.
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Paper Nr: 39
Title:

CSG Ray Tracing Revisited: Interactive Rendering of Massive Models Made of Non-planar Higher Order Primitives
Authors:

Seyedmorteza Mostajabodaveh, Andreas Dietrich, Thomas Gierlinger, Frank Michel and André Stork
Abstract: In many scientific and engineering areas, CAD models are constructed by combining simple primitives using Boolean set operations. Rendering such a dataset usually requires a preprocess, where the surface of the CAD model is approximated by an often highly complex triangle mesh. Real-time ray tracing provides an alternative to triangle rasterization as it allows for the direct visualization of (higher-order) solid and planar primitives without having to triangulate them. Additionally, Boolean compositing operations can be performed implicitly per ray, primitives have low storage requirements, and curved surfaces appear pixel-accurate. In this paper we demonstrate these properties using massive real-world CAD models.
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Area 3 - Animation and Simulation

Full Papers
Paper Nr: 6
Title:

Narrow Band Pressure Computation for Eulerian Fluid Simulation
Authors:

Aditya Prakash and Parag Chaudhuri
Abstract: An Eulerian fluid simulation for incompressible fluids spends a lot of time in enforcing incompressibility by solving a large Poisson’s equation. This involves solving a large system of equations using a solver like conjugate gradients. We introduce a way of accelerating this computation by dividing the grid domain of the fluid simulation into a narrow band of high resolution grid cells near fluid-solid boundaries and a coarser grid everywhere else. Judiciously reducing the number of high resolution grid cells significantly lowers the cost of the pressure projection step, while not sacrificing the simulation quality. The coarse grid values are upgraded to a finer grid before advecting the fluid surface so that enough degrees of freedom are available to resolve surface detail. We present and analyse two methods to perform this upgradation, namely, velocity interpolation and pressure field smoothing. We discuss the merits and demerits of each and quantify the errors introduced in the simulation as a function of size of the narrow band. Finally, since we are primarily interested in visualizing the fluid animation, we produce rendered fluid simulation output to also validate the visual quality of the simulations.
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Paper Nr: 31
Title:

Transposition Based Blendshape Direct Manipulation
Authors:

Ozan Cetinaslan, John Lewis and Verónica Orvalho
Abstract: The blendshape approach is a predominant technique for creating high quality facial animation. Facial poses are generated by altering the corresponding weight parameters manually for each key-frame by using traditional slider interfaces. However, authoring a production quality facial animation with this process requires time-consuming, labor intensive and iterative work the artists. Direct manipulation interfaces address this problem with a “pin-and-drag” operation inspired by the inverse kinematics approaches. The mathematical frameworks of the direct manipulation techniques are mostly based on pseudo-inverse of the blendshape matrices which include all target shape’s vertex positions. However, the pseudo-inverse approaches often give unexpected results during the facial pose editing process because of its unstable behavior. To this end, we propose the transposition approach to enhance the direct manipulation by reducing unexpected movements during weight editing. Our approach extracts the deformation directions from the blendshape matrix, and directly maps the sparse constrained point movements to the extracted directions. Our experiments show that, instead of psuedo-inverse based formulations, transposition based framework gives more smooth and reliable facial poses during the weight editing process. The proposed approach improves the fidelity of the generated facial expressions by keeping the hazardous movements in a minimum level. It is robust, efficient, easy to implement and operate on any blendshape model.
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Paper Nr: 45
Title:

Adding Cartoon-like Motion to Realistic Animations
Authors:

Rufino R. Ansara and Chris Joslin
Abstract: In comparison to traditional animation techniques, motion capture allows animators to obtain a large amount of realistic data in little time. In contrast, classical animation requires a significant amount of manual labour. The motivation behind our research is to look at methods that can fill the gap that separates realistic motion from cartoon animation. With this knowledge, classical animators could produce animated movies and nonrealistic video games in a shorter amount of time. To add cartoon-like qualities to realistic animations, we suggest an algorithm that changes the animation curves of motion capture data by modifying their local minima and maxima. We also propose a curve-based interface that allows users to quickly edit and visualize the changes applied to the animation. Through our user studies, we determine that the proposed curve interface is a good method of interaction. However, we find that in certain cases (both user-related and algorithmic), our animation results exhibit unwanted artefacts. Thus, we present various ways to reduce, avoid or eliminate these issues.
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Short Papers
Paper Nr: 25
Title:

A General Physical-topological Framework using Rule-based Language for Physical Simulation
Authors:

Fatma Ben Salah, Hakim Belhaouari, Agnès Arnould and Philippe Meseure
Abstract: This paper presents a robust framework that combines a topological model (a generalized map or G-map) and a physical one to simulate deformable objects. The framework is general since it allows a general simulation of deformations (1) in different dimensions (2D or 3D), (2) with different types of meshes (triangular, rectangular, tetrahedral, hexahedral, and combinations of them...) and (3) physical models (mass/spring, linear FEM, co-rotational, mass/tensor). Any mechanical information is stored in the topological model and is used in combination with the neighboring relations to compute the equation of motions. To design this model, we have used JERBOA, a rule-based language relying on graph transformations to handle G-maps. This tool has been helpful to build and test different physical models in a little time.
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Paper Nr: 33
Title:

Low Cost Video Animation of People using a RGBD Sensor
Authors:

Cathrine J. Thomsen, Thomas B. Moeslund and Troels H. P. Jensen
Abstract: This paper is an investigation in a low cost solution for performing video animation using a Kinect v2 for Windows, where skeleton, depth and colour data are acquired for three different characters. Segmentation of colour and depth frames were based on establishing the range of a person in the depth frame using the skeleton information, and then train a plane of the floor and exclude points close to it. Transitioning between motions were based on minimizing the Euclidean distance between all feasible transitioning frames, where a source and target frame would be found. Intermediate frames were made to create seamless transitions, where new poses were found by moving pixels in the direction of the optical flow between the transitioning frames. The realism of the proposed animation was verified through a user study to have a higher rate of preference and perceived realism compared to no animation and animation using alpha blending.
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Paper Nr: 65
Title:

Historical Game of Majapahit Kingdom based on Tactical Role-playing Game
Authors:

Mohammad Fadly Syahputra, Muhammad Kurniawan Widhianto and Romi Fadillah Rahmat
Abstract: Majapahit was a kingdom centered in East Java, which once stood around year 1293 to 1500 C. Majapahit kingdom was the last Hindu-Buddhist kingdom that controlled Nusantara and is regarded as one of the greatest kingdom in Indonesia. The lack of modern entertainment content about the history of Majapahit kingdom made historical subject become less attractive. Therefore, we need a modern entertainment as one option to learn about the fascinating history of the kingdom of Majapahit. In this study the authors designed a video game about history of Majapahit kingdom with the genre of tactical role-playing game. Tactical role-playing game is a sub genre of role playing game by using system of turn-based strategy in every battle. In tactical role-playing game, players will take turns with the opponent and can only take action in their turn and each character will have an attribute and level as in role-playing game video game. This study used the A* algorithm to determine the movement direction of the unit and cut-out techniques in the making of animation. This study demonstrated that video games can be used as a media to learn about history.
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Area 4 - Interactive Environments

Full Papers
Paper Nr: 9
Title:

Using a Virtual Maze Task to Assess Spatial Short-term Memory in Adults
Authors:

Sonia Cárdenas-Delgado, Magdalena Méndez-López, M.-Carmen Juan, Elena Pérez-Hernández, Javier Lluch and Roberto Vivó
Abstract: In this paper, we present the Virtual Maze Task that assesses spatial short-term memory in adults involving physical movement and immersion. For physical movement, we used a real bicycle. For immersion, we used a VR HMD. We compared the exposure to the task using two different interaction types (physical active vs. physical inactive conditions). The performance and sensations of the participants were compared in both conditions. We also compared the performance on the virtual task with classical neuropsychological tests. A total of 89 adults participated in our study. The participants’ ability to learn a route within the Virtual Maze Task was tested. Then, the participants assessed their experience scoring the following aspects: interaction and satisfaction. The data were analyzed and we found no differences in satisfaction and interaction scores between the physical active and the physical inactive conditions. However, the condition used for interaction affected the score obtained in the task. There were also significant effects of gender and/or interaction used in other measures of performance on the task. Finally, the performance on the task correlated with the performance on other classical neuropsychological tests for the assessment of short-term memory and spatial memory.
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Paper Nr: 44
Title:

PLAIN: PLugin for predicting the usAbility of Mobile User INterface
Authors:

Makram Soui, Mabrouka Chouchane, Ines Gasmi and Mohamed Wiem Mkaouer
Abstract: Mobile user interfaces have the potential to improve the interaction between user and system by automatically tailoring the graphical user interface presentation according to the mobile devices. Recently, there is a myriad of works that addressed the problem of designing mobile user interfaces to various contexts of use. But, there are very few proposals about evaluating their quality. Using existing evaluation methods such as questionnaires and experts’ evaluation are time-consuming and error-prone. In this paper, we propose an automatic evaluation plugin that allows detecting the defects related to the quality of mobile user interface. The plugin allows the measurement of several metrics that have been known to constitute the state of the art quality attributes that are used to predict the quality of interfaces from the usability perspective. For a given input mobile applications, it generates a list of defects identified using quantitative evaluation metrics and defects types. We evaluated our plugin on four open source mobile applications and the obtained results confirm that our tool can be used to accurately evaluate the quality of interfaces.
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Paper Nr: 57
Title:

A Long-range Vision System for Projection Mapping of Stereoscopic Content in Outdoor Areas
Authors:

Behnam Maneshgar, Leila Sujir, Sudhir P. Mudur and Charalambos Poullis
Abstract: Spatial Augmented Reality, or its more commonly known name Projection Mapping (PM), is a projection technique which transforms a real-life object or scene into a surface for video projection (Raskar et al., 1998b). Although this technique has been pioneered and used by Disney since the seventies, it is in recent years that it has gained significant popularity due to the availability of specialized software which simplifies the otherwise cumbersome calibration process (Raskar et al., 1998a). Currently, PM is being widely used in advertising, marketing, cultural events, live performances, theater, etc as a way of enhancing an object/scene by superimposing visual content (Ridel et al., 2014). However, despite the wide availability of specialized software, several restrictions are still imposed on the type of objects/scenes on which PM can be applied. Most limitations are due to problems in handling objects/scenes with (a) complex reflectance properties and (b) low intensity or distinct colors. In this work, we address these limitations and present solutions for mitigating these problems. We present a complete framework for calibration, geometry acquisition and reconstruction, estimation of reflectance properties, and finally color compensation; all within the context of outdoor long-range PM of stereoscopic content. Using the proposed technique, the observed projections are as close as possible [constrained by hardware limitations] to the actual content being projected; therefore ensuring the perception of depth and immersion when viewed with stereo glasses. We have performed extensive experiments and the results are reported.
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Short Papers
Paper Nr: 11
Title:

Comparison of Wearable Optical See-through and Handheld Devices as Platform for an Augmented Reality Museum Guide
Authors:

Sule Serubugo, Denisa Škantárová, Lasse Kjærsgård Nielsen and Martin Kraus
Abstract: Self-service guides are a common way of providing information about artworks exhibited in museums. Modern advances in handheld mobile applications and wearable optical see-through devices that use augmented reality offer new ways of designing museum guides that are more engaging and interactive than traditional self-service guides such as written descriptions or audio guides. In this study we compare wearable (smart glasses) and handheld (smartphone) devices as a platform for an augmented reality museum guide. We have developed a museum guide for both a smartphone and smart glasses that can identify artwork, direct the visitors’ attention to specific details in it, as well as engage them through a game. The platforms are compared based on participants’ preference feedback and game performance, and are also evaluated by a coordinator from a collaborating museum. We conclude with a discussion of potentials of these platforms as augmented reality museum guides and suggest promising future work.
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Paper Nr: 64
Title:

Measuring the Latency of an Augmented Reality System for Robot-assisted Minimally Invasive Surgery
Authors:

Martin Kibsgaard and Martin Kraus
Abstract: Minimal latency is important for augmented reality systems and teleoperation interfaces as even small increases in latency can affect user performance. Previously, we have developed an augmented reality system that can overlay stereoscopic video streams with computer graphics in order to improve visual communication in training for robot-assisted minimally invasive surgery with da Vinci surgical systems. To make sure that our augmented reality system provides the best possible user experience, we investigated the video latency of the da Vinci surgical system and how the components of our system affect the overall latency. To measure the photon-to-photon latency, we used a microcontroller to determine the time between the activation of a light-emitting diode in front of the endoscopic camera and the corresponding increase in intensity of the surgeon’s display as measured by a phototransistor. The latency of the da Vinci S surgical system was on average 62 ms. None of the components of our overlay system (separately or combined) significantly affected the latency. However, the latency of the assistant’s monitor increased by 14 ms. Passing the video streams through CPU or GPU memory increased the latency to 147 ms and 256 ms, respectively.
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