31-Issue 1

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https://diglib.eg.org/handle/10.2312/170

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Spatio-Temporal Filtering of Indirect Lighting for Interactive Global Illumination
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Chen, Ying-Chieh; Lei, Su Ian Eugene; Chang, Chun-Fa; Holly Rushmeier and Oliver Deussen
We introduce a screen‐space statistical filtering method for real‐time rendering with global illumination. It is inspired by statistical filtering proposed by Meyer et al. to reduce the noise in global illumination over a period of time by estimating the principal components from all rendered frames. Our work extends their method to achieve nearly real-time performance on modern GPUs. More specifically, our method employs the candid covariance‐free incremental PCA to overcome several limitations of the original algorithm by Meyer et al., such as its high computational cost and memory usage that hinders its implementation on GPUs. By combining the reprojection and per‐pixel weighting techniques, our method handles the view changes and object movement in dynamic scenes as well.
Exploring Different Parameters to Assess Left Ventricle Global and Regional Functional Analysis from Coronary CT Angiography
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Silva, Samuel; Santos, Beatriz Sousa; Madeira, Joaquim; Holly Rushmeier and Oliver Deussen
Coronary CT angiography is widely used in clinical practice for the assessment of coronary artery disease. Several studies have shown that the same exam can also be used to assess left ventricle (LV) function. Even though coronary CT angiography provides data concerning multiple cardiac phases, along the cardiac cycle, LV function is usually evaluated using just the end‐systolic and end‐diastolic phases. This unused wealth of data, mostly due to its complexity and the lack of proper tools, has still to be explored to assess if further insight is possible regarding regional LV functional analysis. Furthermore, different parameters can be computed to characterize LV function and though some are well known by clinicians others still need to be tested concerning their value in clinical scenarios. Based on these premises, we present several parameters characterizing global and regional LV function, computed for several cardiac phases over one cardiac cycle. The data provided by the computed parameters is shown using a set of visualizations allowing synchronized visual exploration of the different data. The main purpose is to provide means for clinicians to explore the data and gather insight over their meaning and their correlation with each other and with diagnosis outcomes.
Event report: 2011 Eurographics Symposium on Parallel Graphics and Visualization
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Kuhlen, Torsten; Holly Rushmeier and Oliver Deussen
Editorial
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Holly Rushmeier and Oliver Deussen
Acoustic Rendering and Auditory–Visual Cross-Modal Perception and Interaction
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Hulusic, Vedad; Harvey, Carlo; Debattista, Kurt; Tsingos, Nicolas; Walker, Steve; Howard, David; Chalmers, Alan; Holly Rushmeier and Oliver Deussen
In recent years research in the three-dimensional sound generation field has been primarily focussed upon new applications of spatialized 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. Furthermore, the 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 findings which may be exploited in other fields. This paper provides a comprehensive overview of the major techniques for generating spatialized 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.
Interactive Ray Tracing of Large Models Using Voxel Hierarchies
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Áfra, Attila T.; Holly Rushmeier and Oliver Deussen
We propose an efficient approach for interactive visualization of massive models with CPU ray tracing. A voxel-based hierarchical level-of-detail (LOD) framework is employed to minimize rendering time and required system memory. In a pre-processing phase, a compressed out-of-core data structure is constructed, which contains the original primitives of the model and the LOD voxels, organized into a kd-tree. During rendering, data is loaded asynchronously to ensure a smooth inspection of the model regardless of the available I/O bandwidth. With our technique, we are able to explore data sets consisting of hundreds of millions of triangles in real-time on a desktop PC with a quad-core CPU.
Lazy Visibility Evaluation for Exact Soft Shadows
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Mora, F.; Aveneau, L.; Apostu, O.; Ghazanfarpour, D.; Holly Rushmeier and Oliver Deussen
This paper presents a novel approach to compute high quality and noise‐free soft shadows using exact visibility computations. This work relies on a theoretical framework allowing to group lines according to the geometry they intersect. From this study, we derive a new algorithm encoding lazily the visibility from a polygon. Contrary to previous works on from-polygon visibility, our approach is very robust and straightforward to implement. We apply this algorithm to solve exactly and efficiently the visibility of an area light source from any point in a scene. As a consequence, results are not sensitive to noise, contrary to soft shadows methods based on area light source sampling. We demonstrate the reliability of our approach on different scenes and configurations.
The State of the Art in Interactive Global Illumination
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Ritschel, Tobias; Dachsbacher, Carsten; Grosch, Thorsten; Kautz, Jan; Holly Rushmeier and Oliver Deussen
The interaction of light and matter in the world surrounding us is of striking complexity and beauty. Since the very beginning of computer graphics, adequate modelling of these processes and efficient computation is an intensively studied research topic and still not a solved problem. The inherent complexity stems from the underlying physical processes as well as the global nature of the interactions that let light travel within a scene. This paper reviews the state of the art in interactive global illumination (GI) computation, i.e., methods that generate an image of a virtual scene in less than 1 s with an as exact as possible, or plausible, solution to the light transport. Additionally, the theoretical background and attempts to classify the broad field of methods are described. The strengths and weaknesses of different approaches, when applied to the different visual phenomena, arising from light interaction are compared and discussed. Finally, the paper concludes by highlighting design patterns for interactive GI and a list of open problems.
Beyond Catmull–Clark? A Survey of Advances in Subdivision Surface Methods
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Cashman, Thomas J.; Holly Rushmeier and Oliver Deussen
Subdivision surfaces allow smooth free‐form surface modelling without topological constraints. They have become a fundamental representation for smooth geometry, particularly in the animation and entertainment industries. This survey summarizes research on subdivision surfaces over the last 15 years in three major strands: analysis, integration into existing systems and the development of new schemes. We also examine the reason for the low adoption of new schemes with theoretical advantages, explain why Catmull–Clark surfaces have become a de facto standard in geometric modelling, and conclude by identifying directions for future research.
TreeMatrix: A Hybrid Visualization of Compound Graphs
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Rufiange, Sébastien; McGuffin, Michael J.; Fuhrman, Christopher P.; Holly Rushmeier and Oliver Deussen
We present a hybrid visualization technique for compound graphs (i.e. networks with a hierarchical clustering defined on the nodes) that combines the use of adjacency matrices, node-link and arc diagrams to show the graph, and also combines the use of nested inclusion and icicle diagrams to show the hierarchical clustering. The graph visualized with our technique may have edges that are weighted and/or directed. We first explore the design space of visualizations of compound graphs and present a taxonomy of hybrid visualization techniques. We then present our prototype, which allows clusters (i.e. subtrees) of nodes to be grouped into matrices or split apart using a radial menu. We also demonstrate how our prototype can be used in the software engineering domain, and compare it to the commercial matrix-based visualization tool Lattix using a qualitative user study.
Shiny Vase, Translucent Candle and Metallic Sculpture
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Bousseau, Adrien; Chapoulie, Emmanuelle; Ramamoorthi, Ravi; Agrawala, Maneesh; Holly Rushmeier and Oliver Deussen
Efficient Depth of Field Rasterization Using a Tile Test Based on Half-Space Culling
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Akenine-Möller, Tomas; Toth, Robert; Munkberg, Jacob; Hasselgren, Jon; Holly Rushmeier and Oliver Deussen
For depth of field (DOF) rasterization, it is often desired to have an efficient tile versus triangle test, which can conservatively compute which samples on the lens that need to execute the sample-in-triangle test. We present a novel test for this, which is optimal in the sense that the region on the lens cannot be further reduced. Our test is based on removing half-space regions of the (u, v)-space on the lens, from where the triangle definitely cannot be seen through a tile of pixels. We find the intersection of all such regions exactly, and the resulting region can be used to reduce the number of sample-in-triangle tests that need to be performed. Our main contribution is that the theory we develop provides a limit for how efficient a practical tile versus defocused triangle test ever can become. To verify our work, we also develop a conceptual implementation for DOF rasterization based on our new theory. We show that the number of arithmetic operations involved in the rasterization process can be reduced. More importantly, with a tile test, multi-sampling anti-aliasing can be used which may reduce shader executions and the related memory bandwidth usage substantially. In general, this can be translated to a performance increase and/or power savings.
Generalized Model-Based Human Motion Recognition with Body Partition Index Maps
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Deng, Liqun; Leung, Howard; Gu, Naijie; Yang, Yang; Holly Rushmeier and Oliver Deussen
Content-based human motion analysis has captured extensive concerns of researchers from the domains of computer animation, human-machine interaction, entertainment, etc. However, it is a non-trivial task due to the spatial and temporal variations in the motion data. In this paper, we propose a generalized model (GM)-based approach to model the variations and accurately recognize motion patterns. We partition the human character model into five parts, and extract the features of the submotions of each specific body part using clustering techniques. These features from the training trials in each class are combined to build the GM. We propose a new penalty based similarity measure for DTW to be used with the GMs for isolated motion recognition. On the other hand, from the GMs five body partition index maps are constructed and used for matching together with a flexible end point detection scheme during continuous motion recognition. In the experiments, we examine the effectiveness and efficiency of the approach in both isolated motion and continuous motion recognition. The results show that our proposed method has good performance compared with other state-of-the-art methods in recognition accuracy and processing speed.
Description and Solution of an Unreported Intrinsic Bias in Photon Mapping Density Estimation with Constant Kernel
(The Eurographics Association and Blackwell Publishing Ltd., 2012) García, R.; Ureña, C.; Sbert, M.; Holly Rushmeier and Oliver Deussen
This paper presents an analysis of the irradiance estimator often used in photon mapping algorithms and concludes that the classical approach with a constant kernel overestimates the correct value. We propose a new estimator that solves this problem and provide both theoretical and empirical studies to verify it.
A Low-Memory, Straightforward and Fast Bilateral Filter Through Subsampling in Spatial Domain
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Banterle, Francesco; Corsini, Massimiliano; Cignoni, Paolo; Scopigno, Roberto; Holly Rushmeier and Oliver Deussen
In this work we present a new algorithm for accelerating the colour bilateral filter based on a subsampling strategy working in the spatial domain. The base idea is to use a suitable subset of samples of the entire kernel in order to obtain a good estimation of the exact filter values. The main advantages of the proposed approach are that it has an excellent trade-off between visual quality and speed-up, a very low memory overhead is required and it is straightforward to implement on the GPU allowing real-time filtering. We show different applications of the proposed filter, in particular efficient cross-bilateral filtering, real-time edge-aware image editing and fast video denoising. We compare our method against the state of the art in terms of image quality, time performance and memory usage.
Efficient Image-Based Proximity Queries with Object-Space Precision
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Morvan, T.; Reimers, M.; Samset, E.; Holly Rushmeier and Oliver Deussen
We present an efficient algorithm for object-space proximity queries between multiple deformable triangular meshes. Our approach uses the rasterization capabilities of the GPU to produce an image-space representation of the vertices. Using this image-space representation, inter-object vertex-triangle distances and closest points lying under a user-defined threshold are computed in parallel by conservative rasterization of bounding primitives and sorted using atomic operations. We additionally introduce a similar technique to detect penetrating vertices. We show how mechanisms of modern GPUs such as mipmapping, Early-Z and Early-Stencil culling can optimize the performance of our method. Our algorithm is able to compute dense proximity information for complex scenes made of more than a hundred thousand triangles in real time, outperforming a CPU implementation based on bounding volume hierarchies by more than an order of magnitude.

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