EG2012

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https://diglib.eg.org/handle/10.2312/292

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Virtual Architecture in the Free Space
(The Eurographics Association, 2012) Clini, Paolo; Quattrini, Ramona; Nespeca, Romina; Andrea Fusiello and Michael Wimmer
The multi-projection image techniques offer interesting possibilities for architecture communication and augmented reality. This poster shows experimental solutions for pseudo-holographic projection 360 degree so-called "holographic bell", and projection screen. The more intense research regarding the technical and technological possibilities and the materials of the semi-reflecting plates is being carried out in the EARCOM laboratory of DICEA of Univpm in Ancona. The main goal is to design a good container, ensuring that the content is predominant: low-cost bells, with the maximum projection surface and minimizing the structure.
Hybrid CPU/GPU KD-Tree Construction for Versatile Ray Tracing
(The Eurographics Association, 2012) Roccia, Jean-Patrick; Paulin, Mathias; Coustet, Christophe; Carlos Andujar and Enrico Puppo
We propose an hybrid CPU-GPU ray-tracing implementation based on an optimal Kd-Tree as acceleration structure. The construction and traversal of this KD-tree takes benefit from both the CPU and the GPU to achieve high-performance ray-tracing on mainstream hardware. Our approach, flexible enough to use only a single computing unit (CPU or GPU), is able to efficiently distribute workload between CPUs and GPUs for fast KD-tree construction and traversal.
Evaluation of an Augmented Reality Enhanced Tabletop System as a Collaborative Learning Tool: A Case Study on Mathematics at the Primary School
(The Eurographics Association, 2012) Salvador, Gustavo; Pérez, David; Ortega, Mario; Soto, Emilio; Alcañiz, Mariano; Contero, Manuel; Giovanni Gallo and Beatriz Sousa Santos
Tabletop systems provide a big multi-touch surface suitable for multiple users to gather around it that can interact with the information collaboratively in a face-to-face manner. This kind of device is well adapted to be exploited in education, combining the advantages of e-learning systems with collaborative learning environments, which are adequate in educational paradigms based on constructivism and knowledge building. This article presents the capabilities of our in house developed tabletop system as a collaborative learning tool, which has been enriched with Augmented Reality capabilities and designed to follow the principles of Ubiquitous Computing and Natural Interfaces. The evaluation of the system was performed in a real educational context. Experience was driven to compare the tabletop learning scenario to other standard learning approaches. The evaluation method was centered on three parameters: efficiency, usability/satisfaction and motivation. Results conclude that tabletops represent a promising technology that can be applied successfully in educational contexts.
Fast Response and Quick Progressive Transitions using Body Part Motion Graphs
(The Eurographics Association, 2012) Fernández-Baena, Adso; Miralles, David; Carlos Andujar and Enrico Puppo
Interactive applications where 3D character animation plays an important role need avatars ready to perform different activities. This objective has been accomplished in different works [LCR*02] [ZS09] that look for transition points in motion capture clips to allow transitions between them. These works ensure realism and smoothness but their responses and transition durations depend on transition points. Working with partial motions, such as body part motions, allows finding specific transition points for each part in order to optimize whole body transitions in a progressive way. This can be achieved with body part motion graphs (BPMG’s) [FBM11]. In this work we want to show that progressive transitions generated by BPMG’s have fast response and quick execution. In order to demonstrate this we have compared BPMG’s transitions against standard motion graphs (SMG) transitions. The results we have obtained show that our method allows more reaction velocity and execution. Moreover BPMG’s transitions are smoother than SMG transitions.
Metering for Exposure Stacks
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Gallo, Orazio; Tico, Marius; Manduchi, Roberto; Gelfand, Natasha; Pulli, Kari; P. Cignoni and T. Ertl
When creating a High-Dynamic-Range (HDR) image from a sequence of differently exposed Low-Dynamic-Range (LDR) images, the set of LDR images is usually generated by sampling the space of exposure times with a geometric progression and without explicitly accounting for the distribution of irradiance values of the scene. We argue that this choice can produce sub-optimal results both in terms of the number of acquired pictures and the quality of the resulting HDR image. This paper presents a method to estimate the full irradiance histogram of a scene, and a strategy to select the set of exposures that need to be acquired. Our selection usually requires a smaller or equal set of LDRs, yet produces higher quality HDR images.
A Cell-Based Light Interaction Model for Human Blood
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Yim, Daniel; Baranoski, Gladimir V. G.; Kimmel, Brad W.; Chen, T. Francis; Miranda, Erik; P. Cignoni and T. Ertl
The development of predictive appearance models for organic tissues is a challenging task due to the inherent complexity of these materials. In this paper, we closely examine the biophysical processes responsible for the appearance attributes of whole blood, one the most fundamental of these materials. We describe a new appearance model that simulates the mechanisms of light propagation and absorption within the cellular and fluid portions of this specialized tissue. The proposed model employs a comprehensive, and yet flexible first principles approach based on the morphological, optical and biochemical properties of blood cells. This approach allows for environment driven changes in the cells' anatomy and orientation to be appropriately included into the light transport simulations. The correctness and predictive capabilities of the proposed model are quantitatively and qualitatively evaluated through comparisons of modeled results with actual measured data and experimental observations reported in the scientific literature. Its incorporation into rendering systems is illustrated through images of blood samples depicting appearance variations controlled by physiologically meaningful parameters. Besides the contributions to the modeling of material appearance, the research presented in this paper is also expected to have applications in a wide range of biomedical areas, from optical diagnostics to the visualization and noninvasive imaging of blood-perfused tissues.
Interactive Multi-perspective Imagery from Photos and Videos
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Lieng, Henrik; Tompkin, James; Kautz, Jan; P. Cignoni and T. Ertl
Photographs usually show a scene from a single perspective. However, as commonly seen in art, scenes and objects can be visualized from multiple perspectives. Making such images manually is time consuming and tedious. We propose a novel system for designing multi-perspective images and videos. First, the images in the input sequence are aligned using structure from motion. This enables us to track feature points across the sequence. Second, the user chooses portal polygons in a target image into which different perspectives are to be embedded. The corresponding image regions from the other images are then copied into these portals. Due to the tracking feature and automatic warping, this approach is considerably faster than current tools. We explore a wide range of artistic applications using our system with image and video data, such as looking around corners and up and down stair cases, recursive multi-perspective imaging, cubism and panoramas.
Multiview-Consistent Color Sampling for Alpha Matting
(The Eurographics Association, 2012) Kettern, Markus; Eisert, Peter; Andrea Fusiello and Michael Wimmer
We propose a method for incorporating multiview information into color sampling methodologies for alpha matting. We extend the typical trimap input for matting algorithms to 3D space, enabling the association of stripes of pixels in semi-transparent regions like hair between different views without knowing or inferring their spatial structure. We also formulate a new cost function penalizing deviations of foreground color estimates between associated pixel stripes and its possible integration into a state-of-the-art color sampling approach.
Black is Green: Adaptive Color Transformation For Reduced Ink Usage
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Shapira, Lior; Oicherman, Boris; P. Cignoni and T. Ertl
A vast majority of color transformations applied to an image in the digital press industry are static and precalculated. In order to achieve the best quality on a wide variety of different images, these transformations tend to be highly conservative with respect to the use of black ink. This results in excessive use of inks, which has a negative economic and environmental impact. We present a method for dynamic computation of color transformation based on image content, with the aim to reduce ink usage. We analyze the image, and predict areas in which quality artifacts that may result from such a reduction will be masked by the image content. These areas include detailed textures, noisy areas and structure. We then replace the image CMYK values by a new combination with increased black. Our algorithm ensures negligible color shifts in the resulting image, and no visible reduction in quality. We achieve an average of over 10% ink savings.
Procedural Interpolation of Historical City Maps
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Krecklau, Lars; Manthei, Christopher; Kobbelt, Leif; P. Cignoni and T. Ertl
We propose a novel approach for the temporal interpolation of city maps. The input to our algorithm is a sparse set of historical city maps plus optional additional knowledge about construction or destruction events. The output is a fast forward animation of the city map development where roads and buildings are constructed and destroyed over time in order to match the sparse historical facts and to look plausible where no precise facts are available. A smooth transition between any real-world data could be interesting for educational purposes, because our system conveys an intuition of the city development. The insertion of data, like when and where a certain building or road existed, is efficiently performed by an intuitive graphical user interface. Our system collects all this information into a global dependency graph of events. By propagating time intervals through the dependency graph we can automatically derive the earliest and latest possible date for each event which are guaranteeing temporal as well as geographical consistency (e.g. buildings can only appear along roads that have been constructed before). During the simulation of the city development, events are scheduled according to a score function that rates the plausibility of the development (e.g. cities grow along major roads). Finally, the events are properly distributed over time to control the dynamics of the city development. Based on the city map animation we create a procedural city model in order to render a 3D animation of the city development over decades.
Importance Caching for Complex Illumination
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Georgiev, Iliyan; Krivánek, Jaroslav; Popov, Stefan; Slusallek, Philipp; P. Cignoni and T. Ertl
Realistic rendering requires computing the global illumination in the scene, and Monte Carlo integration is the best-known method for doing that. The key to good performance is to carefully select the costly integration samples, which is usually achieved via importance sampling. Unfortunately, visibility is difficult to factor into the importance distribution, which can greatly increase variance in highly occluded scenes with complex illumination. In this paper, we present importance caching - a novel approach that selects those samples with a distribution that includes visibility, while maintaining efficiency by exploiting illumination smoothness. At a sparse set of locations in the scene, we construct and cache several types of probability distributions with respect to a set of virtual point lights (VPLs), which notably include visibility. Each distribution type is optimized for a specific lighting condition. For every shading point, we then borrow the distributions from nearby cached locations and use them for VPL sampling, avoiding additional bias. A novel multiple importance sampling framework finally combines the many estimators. In highly occluded scenes, where visibility is a major source of variance in the incident radiance, our approach can reduce variance by more than an order of magnitude. Even in such complex scenes we can obtain accurate and low noise previews with full global illumination in a couple of seconds on a single mid-range CPU.
Robust Image Retargeting via Axis-Aligned Deformation
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Panozzo, Daniele; Weber, Ofir; Sorkine, Olga; P. Cignoni and T. Ertl
We propose the space of axis-aligned deformations as the meaningful space for content-aware image retargeting. Such deformations exclude local rotations, avoiding harmful visual distortions, and they are parameterized in 1D. We show that standard warping energies for image retargeting can be minimized in the space of axis-aligned deformations while guaranteeing that bijectivity constraints are satisfied, leading to high-quality, smooth and robust retargeting results. Thanks to the 1D parameterization, our method only requires solving a small quadratic program, which can be done within a few milliseconds on the CPU with no precomputation overhead. We demonstrate how the image size and the saliency map can be changed in real time with our approach, and present results on various input images, including the RETARGETME benchmark. We compare our results with six other algorithms in a user study to demonstrate that the space of axis-aligned deformations is suitable for the problem at hand.
Data Driven Surface Reflectance from Sparse and Irregular Samples
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Ruiters, Roland; Schwartz, Christopher; Klein, Reinhard; P. Cignoni and T. Ertl
In recent years, measuring surface reflectance has become an established method for high quality renderings. In this context, especially non-parametric representations got a lot of attention as they allow for a very accurate representation of complex reflectance behavior. However, the acquisition of this data is a challenging task especially if complex object geometry is involved. Capturing images of the object under varying illumination and view conditions results in irregular angular samplings of the reflectance function with a limited angular resolution. Classical data-driven techniques, like tensor factorization, are not well suited for such data sets as they require a resampling of the high dimensional measurement data to a regular grid. This grid has to be on a much higher angular resolution to avoid resampling artifacts which in turn would lead to data sets of enormous size. To overcome these problems we introduce a novel, compact data-driven representation of reflectance functions based on a sum of separable functions which are fitted directly to the irregular set of data without any further resampling. The representation allows for efficient rendering and is also well suited for GPU applications. By exploiting spatial coherence of the reflectance function over the object a very precise reconstruction even of specular materials becomes possible already with a sparse input sampling. This would be impossible using standard data interpolation techniques. Since our algorithm exclusively operates on the compressed representation, it is both efficient in terms of memory use and computational complexity, depending only sub-linearly on the size of the fully tabulated data. The quality of the reflectance function is evaluated on synthetic data sets as ground truth as well as on real world measurements.
Procedural Texture Preview
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Lasram, Anass; Lefebvre, Sylvain; Damez, Cyrille; P. Cignoni and T. Ertl
Procedural textures usually require spending time testing parameters to realize the diversity of appearances. This paper introduces the idea of a procedural texture preview: A single static image summarizing in a limited pixel space the appearances produced by a given procedure. Unlike grids of thumbnails our previews present a continuous image of appearances, analog to a map. The main challenge is to ensure that most appearances are visible, are allocated a similar pixel area, and are ordered in a smooth manner throughout the preview. To reach this goal, we introduce a new layout algorithm accounting simultaneously for these criteria. After computing a layout of appearances, we rely on by-example texture synthesis to produce the final preview. We demonstrate our approach on a database of production-level procedural textures.
Visualization Curriculum Panel - or The Changes We Have Made to Our Visualization Courses Over the Last 10 Years
(The Eurographics Association, 2012) Domik, Gitta; Ebert, David; Kohlhammer, Jörn; Rushmeier, Holly; Santos, Beatriz Sousa; Weiskopf, Daniel; Giovanni Gallo and Beatriz Sousa Santos
The last ten years have seen profound changes in algorithms, techniques, and applications of visualization. Additionally, we see changes in the sophistication and expectations of our students in visualization courses. This panel will reflect changes in teaching visualization courses through the personal reflections of renowned researchers and educators on their alterations on course content over the past 10 years
Skeleton Based Importance Sampling for Path Tracing
(The Eurographics Association, 2012) Biri, Venceslas; Chaussard, John; Carlos Andujar and Enrico Puppo
When working with large and complex scenes, situations arise where light flux takes complex paths to reach the observer. In such cases, traditional stochastic algorithms, like ray tracing algorithms, will have difficulties to compute noise-free images. Our present research aims to solve this problem using the 3d scene skeleton as a coarse representation. Indeed, curvilinear skeletons can be used to find light paths with higher energy. This article presents our research to use these skeletons for any ray tracing algorithm, allowing a knowledge-based choice when choosing light paths. Our method adds little computation time while producing a more accurate image.
Adaptation of Electrical Laboratory Systems through Augmented Reality for Optimization of Engineering Teaching University
(The Eurographics Association, 2012) Martín-Gutiérrez, Jorge; Fabiani, Peña; Meneses-Fernández, M. Dolores; Pérez-López, David C.; Abselán, Luis; Giovanni Gallo and Beatriz Sousa Santos
This paper introduces an Augmented Reality (AR) application for teaching practices of electrical engineering. In order to improve the autonomy of students and their self-ability we have developed several new practical AR-manuals for being used in the Electric Machines Laboratory. We have used these AR-manuals and the classic ones finding an improvement in learning and motivation of students. The augmented information consists of 3D models, animations and sounds which are superimposed over real objects helping the students in the training of specific tasks. The AR application and the learning environment have been designed based on the principles of interaction between man and machine so the virtual information is presented in an attractive way. Every user provided with a tablet PC or HMD with webcam will be able to visualize on screen the virtual objects added to the real scene. Only one mark has been included in the setting which allows visualization of the virtual information so just one gesture from the user is needed for changing the information. The interactive AR interface has been tested in the laboratory of electrical engineering at a Spanish university.
Real-Time Metaball Ray Casting with Fragment Lists
(The Eurographics Association, 2012) Szécsi, László; Illés, Dávid; Carlos Andujar and Enrico Puppo
In this paper we describe a method for rendering particle-based medium representations. The algorithm builds per-pixel lists of relevant metaballs, then incrementally constructs a piecewise polynomial approximation of summed metaball densities along rays, and finds intersections with the isosurface using those. This new approach scales well for a high number of particles, it can handle local extremities of depth complexity robustly, and it does not suffer from the inaccuracies and limitations of screen-space filtering approximation methods.
Meshless Statistical Occlusion Computation
(The Eurographics Association, 2012) Fouquet, François; Farrugia, Jean-Philippe; Iehl, Jean-Claude; Dupuy, Jonathan; Andrea Fusiello and Michael Wimmer
This paper presents a new method to evaluate visibility from a point cloud by using a meshless statistical representation. The resulting evaluation uses much less memory than previous work while still producing high quality images, making it suitable for memory limited systems. The obtained results are exposed through the evaluation of shadow maps using a point cloud created from range images and are compared to current methods, which rely on mesh reconstruction techniques.
crdbrd: Shape Fabrication by Sliding Planar Slices
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Hildebrand, Kristian; Bickel, Bernd; Alexa, Marc; P. Cignoni and T. Ertl
We introduce an algorithm and representation for fabricating 3D shape abstractions using mutually intersecting planar cut-outs. The planes have prefabricated slits at their intersections and are assembled by sliding them together. Often such abstractions are used as a sculptural art form or in architecture and are colloquially called 'cardboard sculptures'. Based on an analysis of construction rules, we propose an extended binary space partitioning tree as an efficient representation of such cardboard models which allows us to quickly evaluate the feasibility of newly added planar elements. The complexity of insertion order quickly increases with the number of planar elements and manual analysis becomes intractable. We provide tools for generating cardboard sculptures with guaranteed constructibility. In combination with a simple optimization and sampling strategy for new elements, planar shape abstraction models can be designed by iteratively adding elements. As an output, we obtain a fabrication plan that can be printed or sent to a laser cutter. We demonstrate the complete process by designing and fabricating cardboard models of various well-known 3D shapes.

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