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Item Statistical Analysis of Parallel Data Uploading using OpenGL(The Eurographics Association, 2019) Wiedemann, Markus; Kranzlmüller, Dieter; Childs, Hank and Frey, SteffenModern real-time visualizations of large-scale datasets require constant high frame rates while their datasets might exceed the available graphics memory. This requires sophisticated upload strategies from host memory to the memory of the graphics cards. A possible solution uses outsourcing of all data uploads onto concurrent threads and disconnecting prohibitive data dependencies. OpenGL provides a variety of functions and parameters but not all allow minimal interference on rendering. In this work, we present a thorough and statistically sound analysis of various effects introduced by choosing different input parameters, such as size, partitioning and number of threads for uploading, as well as combinations of buffer usage hints and uploading functions. This approach provides insight into the problem and offers a basis for future optimizations.Item Fast Continuous Collision Detection among Deformable Models using Graphics Processors(The Eurographics Association, 2006) Govindaraju, Naga K.; Kabul, Ilknur; Lin, Ming C.; Manocha, Dinesh; Ming Lin and Roger HubboldWe present an interactive algorithm to perform continuous collision detection between general deformable models using graphics processors (GPUs). We model the motion of each object in the environment as a continuous path and check for collisions along the paths. Our algorithm precomputes the chromatic decomposition for each object and uses visibility queries on GPUs to quickly compute potentially colliding sets of primitives. We introduce a primitive classification technique to perform efficient continuous self-collision. We have implemented our algorithm on a 3:0 GHz Pentium IV PC with a NVIDIA 7800 GPU, and we highlight its performance on complex simulations composed of several thousands of triangles. In practice, our algorithm is able to detect all contacts, including self-collisions, at image-space precision in tens of milli-seconds.Item Harmonics Virtual Lights: Fast Projection of Luminance Field on Spherical Harmonics for Efficient Rendering(© 2022 Eurographics ‐ The European Association for Computer Graphics and John Wiley & Sons Ltd., 2022) Mézières, Pierre; Desrichard, François; Vanderhaeghe, David; Paulin, Mathias; Hauser, Helwig and Alliez, PierreIn this paper, we introduce harmonics virtual lights (HVL), to model indirect light sources for interactive global illumination of dynamic 3D scenes. Virtual point lights (VPL) are an efficient approach to define indirect light sources and to evaluate the resulting indirect lighting. Nonetheless, VPL suffer from disturbing artefacts, especially with high‐frequency materials. Virtual spherical lights (VSL) avoid these artefacts by considering spheres instead of points but estimates the lighting integral using Monte‐Carlo which results to noise in the final image. We define HVL as an extension of VSL in a spherical harmonics (SH) framework, defining a closed form of the lighting integral evaluation. We propose an efficient SH projection of spherical lights contribution faster than existing methods. Computing the outgoing luminance requires operations when using materials with circular symmetric lobes, and operations for the general case, where is the number of SH bands. HVL can be used with either parametric or measured BRDF without extra cost and offers control over rendering time and image quality, by either decreasing or increasing the band limit used for SH projection. Our approach is particularly well‐designed to render medium‐frequency one‐bounce global illumination with arbitrary BRDF at an interactive frame rate.Item Interactive Modeling of Mechanical Objects(The Eurographics Association and John Wiley & Sons Ltd., 2016) Ureta, Francisca Gil; Tymms, Chelsea; Zorin, Denis; Maks Ovsjanikov and Daniele PanozzoObjects with various types of mechanical joints are among the most commonly built. Joints implement a vocabulary of simple constrained motions (kinematic pairs) that can be used to build more complex behaviors. Defining physically correct joint geometry is crucial both for realistic appearance of models during motion, as these are typically the only parts of geometry that stay in contact, and for fabrication. Direct design of joint geometry often requires more effort than the design of the rest of the object geometry, as it requires design of components that stay in precise contact, are aligned with other parts, and allow the desired range of motion. We present an interactive system for creating physically realizable joints with user-controlled appearance. Our system minimizes or, in most cases, completely eliminates the need for the user to manipulate low-level geometry of joints. This is achieved by automatically inferring a small number of plausible combinations of joint dimensions, placement and orientation from part geometry, with the user making the final high-level selection based on object semantic. Through user studies, we demonstrate that functional results with a satisfying appearance can be obtained quickly by users with minimal modeling experience, offering a significant improvement in the time required for joint construction, compared to standard modeling approaches.Item Parameterized Skin for Rendering Flushing Due to Exertion(The Eurographics Association, 2016) Vieira, Teresa; Angus Forbes and Lyn BartramIt is known that physical exercise increases bloodflow and flushing of the facial skin. When digital artists hand-paint the textures for animation of realistic effects such as flushing due to exertion, they observe real-life references and use their creativity. This process is empirical and time-consuming, with artists often using the same textures across all facial expressions. The problem is that there is a lack of guidelines on how skin color changes due to exertion, that is only surpassed when scans of facial appearance are used. However facial appearance scans are best suited when creating digital doubles and do not easily fit different characters. Here, we present a novel delta-parameterized method that guides artists in painting the textures for animation of flushing due to physical exertion. To design the proposed method we have analyzed skin color differences in L*a*b* color space, from 34 human subjects' portraits before and after physical exercise. We explain the experiment setup configuration, statistical analysis and the resulting delta color differences from which we derived our method parameters. We illustrate how our method suits any skin type and character style. The proposed method was reviewed by texture artists, who find it useful and that it may help render more realistic flushed exertion expressions, compared to state of the art, guesswork techniques.Item Rendering and Extracting Extremal Features in 3D Fields(The Eurographics Association and John Wiley & Sons Ltd., 2018) Kindlmann, Gordon L.; Chiw, Charisee; Huynh, Tri; Gyulassy, Attila; Reppy, John; Bremer, Peer-Timo; Jeffrey Heer and Heike Leitte and Timo RopinskiVisualizing and extracting three-dimensional features is important for many computational science applications, each with their own feature definitions and data types. While some are simple to state and implement (e.g. isosurfaces), others require more complicated mathematics (e.g. multiple derivatives, curvature, eigenvectors, etc.). Correctly implementing mathematical definitions is difficult, so experimenting with new features requires substantial investments. Furthermore, traditional interpolants rarely support the necessary derivatives, and approximations can reduce numerical stability. Our new approach directly translates mathematical notation into practical visualization and feature extraction, with minimal mental and implementation overhead. Using a mathematically expressive domain-specific language, Diderot, we compute direct volume renderings and particlebased feature samplings for a range of mathematical features. Non-expert users can experiment with feature definitions without any exposure to meshes, interpolants, derivative computation, etc. We demonstrate high-quality results on notoriously difficult features, such as ridges and vortex cores, using working code simple enough to be presented in its entirety.Item Partial Shape Matching Using Transformation Parameter Similarity(Copyright © 2015 The Eurographics Association and John Wiley & Sons Ltd., 2015) Guerrero, Paul; Auzinger, Thomas; Wimmer, Michael; Jeschke, Stefan; Deussen, Oliver and Zhang, Hao (Richard)In this paper, we present a method for non‐rigid, partial shape matching in vector graphics. Given a user‐specified query region in a 2D shape, similar regions are found, even if they are non‐linearly distorted. Furthermore, a non‐linear mapping is established between the query regions and these matches, which allows the automatic transfer of editing operations such as texturing. This is achieved by a two‐step approach. First, pointwise correspondences between the query region and the whole shape are established. The transformation parameters of these correspondences are registered in an appropriate transformation space. For transformations between similar regions, these parameters form surfaces in transformation space, which are extracted in the second step of our method. The extracted regions may be related to the query region by a non‐rigid transform, enabling non‐rigid shape matching.In this paper, we present a method for non‐rigid, partial shape matching in vector graphics. Given a user‐specified query region in a 2D shape, similar regions are found, even if they are non‐linearly distorted. Furthermore, a non‐linear mapping is established between the query regions and these matches, which allows the automatic transfer of editing operations such as texturing. This is achieved by a two‐step approach. First, pointwise correspondences between the query region and the whole shape are established. The transformation parameters of these correspondences are registered in an appropriate transformation space. For transformations between similar regions, these parameters form surfaces in transformation space, which are extracted in the second step of our method. The extracted regions may be related to the query region by a non‐rigid transform, enabling non‐rigid shape matching.Item Progressive Hulls for Intersection Applications(Blackwell Publishers, Inc and the Eurographics Association, 2003) Platis, Nikos; Theoharis, TheoharisProgressive meshes are an established tool for triangle mesh simplification. By suitably adapting the simplification process, progressive hulls can be generated which enclose the original mesh in gradually simpler, nested meshes. We couple progressive hulls with a selective refinement framework and use them in applications involving intersection queries on the mesh. We demonstrate that selectively refinable progressive hulls considerably speed up intersection queries by efficiently locating intersection points on the mesh. Concerning the progressive hull construction, we propose a new formula for assigning edge collapse priorities that significantly accelerates the simplification process, and enhance the existing algorithm with several conditions aimed at producing higher quality hulls. Using progressive hulls has the added advantage that they can be used instead of the enclosed object when a lower resolution of display can be tolerated, thus speeding up the rendering process.ACM CSS: I.3.3 Computer Graphics-Picture/Image Generation, I.3.5 Computer Graphics-Computational Geometry and Object Modeling, I.3.7 Computer Graphics-Three-Dimensional Graphics and RealismItem Simulation of Facial Muscle Actions Based on Rational Free Form Deformations(Blackwell Science Ltd and the Eurographics Association, 1992) Kalra, Prem; Mangili, Angelo; Thalmann, Nadia Magnenat; Thalmann, DanielThis paper describes interactive facilities for simulating abstract muscle actions using Rational Free Form Deformations (RFFD). The particular muscle action is simulated as the displacement of the control points of the control-unit for an RFFD defined on a region of interest. One or several simulated muscle actions constitute a Minimum Perceptible Action (MPA), which is defined as the atomic action unit, similar to Action Unit (AU) of the Facial Action Coding System (FACS), to build an expression.Item Interactive Rendering of Volumetric Data Sets(The Eurographics Association, 1994) Juskiw, "Scott; Durdle, Nelson G.; W. StrasserThe bela architecture for interactive rendering of regularly structured volumetric data sets is presented. The proposed architecture is scalable and uses custom processors to achieve high-speed shading, projection. and composition of voxel primitives. A general purpose image composition network supports the accumulation of both volumetric and geometric elements into the final rendered scene. Data access contentions between processors are eliminated via the use of an enhanced dual object space and image space partitioning scheme that does not require replication or redistribution of rendered data. The bela architecture is intended for rendering large data sets and meets the performance requirements of a full frame interactive image generation system.