EG2011

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https://diglib.eg.org/handle/10.2312/284

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AA Patterns
(The Eurographics Association, 2011) Ahmed, Abdalla G. M.; R. Laramee and I. S. Lim
AA Patterns is the name of a recently developed algorithmic art technique that employs a simple linear 2D transform to generate ornamental patterns of pixels. The patterns are controlled by a single real parameter between 1 and 2. By appropriately anatomizing this parameter it is shown that this single parameter actually allows much control over the patterns. Some potential uses are pointed out, too.
Accelerated 5D Ray Tree construction on the GPU
(The Eurographics Association, 2011) Kammaje, Ravi P.; Mora, Benjamin; R. Laramee and I. S. Lim
Ray tracing random rays has been a challenge. Due to their reduced coherence, the normal methods of acceleration like packet tracing that make use of coherence of the rays do not work well. These random rays are encountered in global illumination methods. 5D ray classification, first introduced by Arvo and Kirk [AK87], can classify these rays into coherent groups. We introduce a method that builds a hierarchical structure identifying coherence in random rays very quickly using the increased processing power of the GPU.
Acoustic Rendering and Auditory-Visual Cross-Modal Perception and Interaction
(The Eurographics Association, 2011) Hulusic, Vedad; Harvey, Carlo; Tsingos, Nicolas; Debattista, Kurt; Walker, Steve; Howard, David; Chalmers, Alan; N. John and B. Wyvill
In recent years research in the 3-Dimensional sound generation field has been primarily focussed upon new applications of spatialised sound. In the computer graphics community the use of such techniques is most commonly found being applied to virtual, immersive environments. However, the field is more varied and diverse than this and other research tackles the problem in a more complete, and computationally expensive manner. However, simulation of light and sound wave propagation is still unachievable at a physically accurate spatio-temporal quality in real-time. Although the Human Visual System (HVS) and the Human Auditory System (HAS) are exceptionally sophisticated, they also contain certain perceptional and attentional limitations. Researchers, in fields such as psychology, have been investigating these limitations for several years and have come up with some findings which may be exploited in other fields. This STAR provides a comprehensive overview of the major techniques for generating spatialised sound and, in addition, discusses perceptual and cross-modal influences to consider. We also describe current limitations and provide an in-depth look at the emerging topics in the field.
Alpha Compression with Variable Data Formats
(The Eurographics Association, 2011) Jiang, Yifei; Gui, Mindan; Chen, Shuai; Hu, Weiwu; N. Avis and S. Lefebvre
Based on the insight into the essential differences between transparency and color, we present a novel alpha compression scheme, called EAC (Enhanced Alpha Compression), as an improvement to that of DXT5. EAC defines new compression data formats, and employs clustering algorithms combined with linear interpolation method used in DXT5 to compress 16 input alpha values to 64 bits. The compressed block has three possible formats, corresponding to two process modes in decompression. Results show that EAC improves the average PSNR with about 0.2 dB compared to alpha compression of DXT5 over a set of test images. Moreover, the average cell area of hardware implementation is reduced by about 25 percent, and the power consumption is lowered by 21.66 percent 26.75 percent.
Application of Active Appearance Model to Automatic Face Replacement
(The Eurographics Association, 2011) Govindaraj, Dinesh; R. Laramee and I. S. Lim
Active appearance models (AAM) are statistical model for capturing shape as well as appearance of deformable objects like human face. The power of AAM lies in the fact that it can synthesis or explain any given object shape and appearance with compact set of parameters. AAM is used widely in the application of face recognition and facial expression recognition. We present a novel method of using AAM to the application of Face Replacement. Face Replacement is process of replacing the face in an image with any face of our choice while retaining the original pose and expression intact. Face replacement of any two given images takes only few hundreds of milliseconds without compromising quality.
Architectural Styles Dependent Shape Grammar Representation of Facades
(The Eurographics Association, 2011) Duskova, E.; Zara, J.; R. Laramee and I. S. Lim
In this poster, we present an idea to utilize formal rules and descriptions for architectural styles from various time periods. We focus on facades of historical buildings with identical purpose located in a specific geographical area. We have chosen the CGA shape grammar as a formal language to represent and visualise the rules and we demonstrate our approach on facades of the residence-type historical buildings located in Prague. Our aim is to show that differences in formal descriptions of various buildings are tightly related to differences in architectural styles. Having a proper metrics for such CGA grammars, we will be able to generate new virtual buildings of certain architectural style and to control their possible transitions among distinct styles.
The Art and Science of Digital Production Arts
(The Eurographics Association, 2011) Davis, Tim A.; House, Donald H.; S. Maddock and J. Jorge
As its name implies, digital production arts incorporates both technical and artistic aspects. The challenge of any program in this discipline is to balance these two components in such a way that each enhances the other the technical aspect provides new tools and techniques for artists to explore, while the art aspect drives digital tech-nology in new directions. Students interested in digital production arts require both generalized and specialized education in each field, with additional emphasis on synthesis of both. The Digital Production Arts program at Clemson University strives to accomplish this goal through an interdisciplinary program with major components in art and computer science. Graduates of our program seek to apply their skills in special effects and computer ani-mation in the rapidly expanding field of film, television, and gaming.
Artistic Stylisation of Images and Video
(The Eurographics Association, 2011) Collomosse, John; Kyprianidis, Jan Eric; Ralph Martin and Juan Carlos Torres
The half-day tutorial provides an introduction to Non- Photorealistic Rendering (NPR), targeted at both students and experienced researchers of Computer Graphics who have not previously explored NPR in their work. The tutorial focuses on two-dimensional (2D) NPR, specifically the transformation of photos or videos into synthetic art concepts will be introduced gently and no prior knowledge is assumed beyond a working knowledge of filtering and convolution operations. Some elements of the course will touch upon GPU implementation, but GPU concepts will be described at a high level of abstraction without need for detailed working knowledge of GPU programming.
Automatic Stream Surface Seeding
(The Eurographics Association, 2011) Edmunds, Matt; McLoughlin, Tony; Laramee, Robert S.; Chen, Guoning; Zhang, Eugene; Max, Nelson; N. Avis and S. Lefebvre
The visualisation of 3D flow poses many challenges. Difficulties can stem from attempting to capture all flow features, the speed of computation, and spatial perception. Streamlines and stream surfaces are standard tools for visualising 3D flow. Although a variety of automatic seeding approaches have been proposed for streamlines, little work has been presented for stream surfaces. We present a novel automatic approach to the seeding of stream surfaces in 3D flow fields. We first describe defining seeding curves at the domain boundaries from isolines generated from a derived scalar field. We then detail the generation of stream surfaces integrated through the flow and discuss the associated challenges of surface termination and occlusion. We also present the results of this algorithm, how we achieve satisfactory domain coverage and capture the features of the flow field. Strategies for resolving occlusion resulting from seeding multiple surfaces are also presented and analysed.
AVM-Explorer: Multi-Volume Visualization of Vascular Structures for Planning of Cerebral AVM Surgery
(The Eurographics Association, 2011) Weiler, Florian; Rieder, Christian; David, C. A.; Wald, C.; Hahn, Horst K.; K. Buehler and A. Vilanova
Arteriovenous malformations (AVMs) of the brain are rare vascular disorders characterized by the presence of direct connections between cerebral arteries and veins. Preoperative planning of AVM surgery is a challenging task. The neurosurgeon needs to gain a detailed understanding of both the pathoanatomy of the lesion as well as its location and spatial relation to critical functional areas and white matter fiber bundles at risk. A crucial element during this planning phase is the precise identification of feeding arteries, draining veins, and arteries en passage". To this end, a variety of imaging modalities for displaying neurovascular structures exists, both tomographic as well as projection based. However, the conventional 2D slice based review of such data is not well suited to help understanding the complex angioarchitecture of an AVM. In this paper, we demonstrate how stateof- the-art techniques from the fields of computer graphics and image processing can support neurosurgeons with the challenge of creating a mental 3D model of the lesion and understanding its internal structure. To evaluate the clinical value of our method, we present results from three case studies along with the medical assessment of an experienced neurosurgeon.
Avoiding Chromaticity Creep with PseudoGrey
(The Eurographics Association, 2011) Grimstead, I. J.; Avis, N. J.; A. Day and R. Mantiuk and E. Reinhard and R. Scopigno
We examine the calibration of Commodity, Off-The-Shelf (COTS) monitors to the DICOM GreyScale Display Function (GSDF) standard (as used for medical imaging). We note that uncalibrated and calibrated (using commercial and non-commercial tools) monitors exhibit Chromaticity creep along the black body locus in CIE 1931 colourspace; this is at odds with high-end medical monitors which do not introduce colour-but cost significantly more than COTS colour monitors. Alternative algorithms are investigated to produce a DICOM GSDF compliant calibration, where we take into account both luminance and chromaticity. Using PseudoGrey we generate thousands of shades of grey on a colour monitor to produce a high dynamic range, albeit in greyscale, improving on the standard 256 shades of grey. In this work, we now restrict our introduction of colour to minimise chromaticity deviation from a given white point. We have found various chromatic anomalies with COTS monitors, and discuss our findings along with algorithmic variations to cope with such issues. We believe this work contributes to the availability of a robust method to calibrate COTS colour monitors to the GSDF and hence any required intensity curve whilst retaining a pure colour, enabling greyscale images with over 256 shades to be accurately displayed. This may have significant cost, and potentially improved diagnostic implications, in the reporting of medical radiological images, and could be used to display high dynamic range greyscale imagery (such as multiple exposure black and white photography).
Believable Virtual Characters in Human-Computer Dialogs
(The Eurographics Association, 2011) Jung, Yvonne; Kuijper, Arjan; Fellner, Dieter W.; Kipp, Michael; Miksatko, Jan; Gratch, Jonathan; Thalmann, Daniel; N. John and B. Wyvill
For many application areas, where a task is most naturally represented by talking or where standard input devices are difficult to use or not available at all, virtual characters can be well suited as an intuitive man-machineinterface due to their inherent ability to simulate verbal as well as nonverbal communicative behavior. This type of interface is made possible with the help of multimodal dialog systems, which extend common speech dialog systems with additional modalities just like in human-human interaction. Multimodal dialog systems consist at least of an auditive and graphical component, and communication is based on speech and nonverbal communication alike. However, employing virtual characters as personal and believable dialog partners in multimodal dialogs entails several challenges, because this requires not only a reliable and consistent motion and dialog behavior but also regarding nonverbal communication and affective components. Besides modeling the mind and creating intelligent communication behavior on the encoding side, which is an active field of research in artificial intelligence, the visual representation of a character including its perceivable behavior, from a decoding perspective, such as facial expressions and gestures, belongs to the domain of computer graphics and likewise implicates many open issues concerning natural communication. Therefore, in this report we give a comprehensive overview how to go from communication models to actual animation and rendering.
(Bi)spectral Rendering in Practice
(The Eurographics Association, 2011) Wilkie, Alexander; Weidlich, Andrea; Ralph Martin and Juan Carlos Torres
Abstract to follow.
Blur-Aware Image Downsampling
(The Eurographics Association and Blackwell Publishing Ltd., 2011) Trentacoste, Matthew; Mantiuk, Rafal; Heidrich, Wolfgang; M. Chen and O. Deussen
Resizing to a lower resolution can alter the appearance of an image. In particular, downsampling an image causes blurred regions to appear sharper. It is useful at times to create a downsampled version of the image that gives the same impression as the original, such as for digital camera viewfinders. To understand the effect of blur on image appearance at different image sizes, we conduct a perceptual study examining how much blur must be present in a downsampled image to be perceived the same as the original. We find a complex, but mostly image-independent relationship between matching blur levels in images at different resolutions. The relationship can be explained by a model of the blur magnitude analyzed as a function of spatial frequency. We incorporate this model in a new appearance-preserving downsampling algorithm, which alters blur magnitude locally to create a smaller image that gives the best reproduction of the original image appearance.
BSSRDF Estimation from Single Images
(The Eurographics Association and Blackwell Publishing Ltd., 2011) Munoz, Adolfo; Echevarria, Jose I.; Seron, Francisco J.; Lopez-Moreno, Jorge; Glencross, Mashhuda; Gutierrez, Diego; M. Chen and O. Deussen
We present a novel method to estimate an approximation of the reflectance characteristics of optically thick, homogeneous translucent materials using only a single photograph as input. First, we approximate the diffusion profile as a linear combination of piecewise constant functions, an approach that enables a linear system minimization and maximizes robustness in the presence of suboptimal input data inferred from the image. We then fit to a smoother monotonically decreasing model, ensuring continuity on its first derivative. We show the feasibility of our approach and validate it in controlled environments, comparing well against physical measurements from previous works. Next, we explore the performance of our method in uncontrolled scenarios, where neither lighting nor geometry are known. We show that these can be roughly approximated from the corresponding image by making two simple assumptions: that the object is lit by a distant light source and that it is globally convex, allowing us to capture the visual appearance of the photographed material. Compared with previous works, our technique offers an attractive balance between visual accuracy and ease of use, allowing its use in a wide range of scenarios including off-the-shelf, single images, thus extending the current repertoire of real-world data acquisition techniques.
Collision-Driven Volumetric Deformation on the GPU
(The Eurographics Association, 2011) Aldrich, Garrett; Pinskiy, Dmitriy; Hamann, Bernd; N. Avis and S. Lefebvre
We present a novel parallel algorithm to animate the deformation of a soft body in response to collision. Our algorithm incorporates elements of physically-based methods, and at the same time, it allows artistic control of general deformation behavior. Our solver has important benefits for practical use, such as evaluation of animation frames in an arbitrary order, effective approximation of volume preservation, and stability under large deformations. To deform production-complexity data at interactive rates, we leverage the computational power of modern GPUs. In our solution we propose a specialized, CUDA-based framework for the efficient access and update of mesh structures.
Combinatorial Bidirectional Path-Tracing for Efficient Hybrid CPU/GPU Rendering
(The Eurographics Association and Blackwell Publishing Ltd., 2011) Pajot, Anthony; Barthe, Loïc; Paulin, Mathias; Poulin, Pierre; M. Chen and O. Deussen
This paper presents a reformulation of bidirectional path-tracing that adequately divides the algorithm into processes efficiently executed in parallel on both the CPU and the GPU. We thus benefit from high-level optimization techniques such as double buffering, batch processing, and asyncronous execution, as well as from the exploitation of most of the CPU, GPU, and memory bus capabilities. Our approach, while avoiding pure GPU implementation limitations (such as limited complexity of shaders, light or camera models, and processed scene data sets), is more than ten times faster than standard bidirectional path-tracing implementations, leading to performance suitable for production-oriented rendering engines.
Component-wise Controllers for Structure-Preserving Shape Manipulation
(The Eurographics Association and Blackwell Publishing Ltd., 2011) Zheng, Youyi; Fu, Hongbo; Cohen-Or, Daniel; Au, Oscar Kin-Chung; Tai, Chiew-Lan; M. Chen and O. Deussen
Recent shape editing techniques, especially for man-made models, have gradually shifted focus from maintaining local, low-level geometric features to preserving structural, high-level characteristics like symmetry and parallelism. Such new editing goals typically require a pre-processing shape analysis step to enable subsequent shape editing. Observing that most editing of shapes involves manipulating their constituent components, we introduce component-wise controllers that are adapted to the component characteristics inferred from shape analysis. The controllers capture the natural degrees of freedom of individual components and thus provide an intuitive user interface for editing. A typical model usually results in a moderate number of controllers, allowing easy establishment of semantic relations among them by automatic shape analysis supplemented with user interaction. We propose a component-wise propagation algorithm to automatically preserve the established inter-relations while maintaining the defining characteristics of individual controllers and respecting the user-specified modeling constraints. We extend these ideas to a hierarchical setup, allowing the user to adjust the tool complexity with respect to the desired modeling complexity. We demonstrate the effectiveness of our technique on a wide range of manmade models with structural features, often containing multiple connected pieces.
Comprehensive Facial Performance Capture
(The Eurographics Association and Blackwell Publishing Ltd., 2011) Fyffe, Graham; Hawkins, Tim; Watts, Chris; Ma, Wan-Chun; Debevec, Paul; M. Chen and O. Deussen
We present a system for recording a live dynamic facial performance, capturing highly detailed geometry and spatially varying diffuse and specular reflectance information for each frame of the performance. The result is a reproduction of the performance that can be rendered from novel viewpoints and novel lighting conditions, achieving photorealistic integration into any virtual environment. Dynamic performances are captured directly, without the need for any template geometry or static geometry scans, and processing is completely automatic, requiring no human input or guidance. Our key contributions are a heuristic for estimating facial reflectance information from gradient illumination photographs, and a geometry optimization framework that maximizes a principled likelihood function combining multi-view stereo correspondence and photometric stereo, using multiresolution belief propagation. The output of our system is a sequence of geometries and reflectance maps, suitable for rendering in off-the-shelf software. We show results from our system rendered under novel viewpoints and lighting conditions, and validate our results by demonstrating a close match to ground truth photographs
Computational Plenoptic Imaging
(The Eurographics Association, 2011) Wetzstein, Gordon; Ihrke, Ivo; Lanman, Douglas; Heidrich, Wolfgang; N. John and B. Wyvill
The plenoptic function is a ray-based model for light that includes the color spectrum as well as spatial, temporal, and directional variation. Although digital light sensors have greatly evolved in the last years, one fundamental limitation remains: all standard CCD and CMOS sensors integrate over the dimensions of the plenoptic function as they convert photons into electrons; in the process, all visual information is irreversibly lost, except for a two-dimensional, spatially-varying subset - the common photograph. In this state of the art report, we review approaches that optically encode the dimensions of the plenpotic function transcending those captured by traditional photography and reconstruct the recorded information computationally.

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