http://www.computer.org/cga IEEE Computer Graphics and Applications bridges the theory and practice of computer graphics. From specific algorithms to full system implementations, CG&A offers a unique combination of peer-reviewed feature articles and informal departments, including news and product announcements. Special applications sidebars relate research stories to commercial development. A cover story focuses on creative applications of the technology by an artist or designer. And graphics all-stars Jim Blinn and Andrew Glassner offer insight and wit in their popular columns. Published six times a year, CG&A is indispensable reading for people working at the leading edge of computer graphics technology and its applications in everything from business to the arts. en-us Wed, 4 Jan 2012 11:00:01 GMT http://csdl.computer.org/common/images/logos/cga.gif List of recently published journal articles http://www.computer.org/cga http://doi.ieeecomputersociety.org/10.1109/MCG.2011.86 Diffusion curves are a new kind of primitive in vector graphics, capable of representing smooth color transitions among boundaries. Their rendering requires solving Poisson's equation, and many previous efforts relied on traditional solvers which commonly require GPU acceleration to achieve real-time rasterization. This obviously restricts deployment on the internet, e.g. as Rich Internet Applications (RIAs), in which various computing environments are involved. Inspired by the observation that diffusion effects have very similar appearance to locally defined interpolation with particular orientation and magnitude, we propose a mesh-based approach combined with mean value coordinates (MVC) interpolant to efficiently render diffusion curve images on CPU. A visibility algorithm is employed to efficiently find and sort neighboring curve nodes for each vertex, and then the colors of vertices are assigned according to MVC interpolation with neighboring curve nodes. Our experiments show comparable rendering results to traditional solvers, while our method is computationally more efficient and runs much faster on a CPU. http://doi.ieeecomputersociety.org/10.1109/MCG.2011.86 http://doi.ieeecomputersociety.org/10.1109/MCG.2012.30 We present a method to reduce noise in stochastic ray tracing that is especially tailored to interactive progressive rendering. High-variance light paths are accumulated in a separate buffer, which is filtered by a high-quality edge preserving filter. Then a combination of the noisy unfiltered samples and the less noisy (but biased) filtered samples is added to the low-variance samples in order to form the final image. A novel per-pixel blending operator combines both contributions in a way that respects a user-defined threshold on perceived noise. Our method is able to provide fast, reliable previews, even in the presence of complex features like specular surfaces and high-frequency textures. At the same time it is consistent in the sense that the bias due to filtering vanishes in the limit. http://doi.ieeecomputersociety.org/10.1109/MCG.2012.30 http://opac.ieeecomputersociety.org/opac?year=2012&volume=32&issue=01&acronym=cga IEEE Computer Graphics and Applications http://www.computer.org/portal/site/cga/ http://doi.ieeecomputersociety.org/10.1109/MCG.2011.110 Computer Graphics has a number of analytical BRDF models at its disposal, some of which are widely considered to be at least reasonably physically plausible. Significant effort has also been invested in measuring the actual reflectance of a wide range of material surfaces. While such measurements have been used to fit ad hoc combinations of BRDF models to the observed reflectance behaviour, we are not aware of a systematic effort to verify the predictions of basic analytical BRDF models based on measurements of real-world samples. In this paper we propose to use ellipsometry as a way to verify both the actual polarising effect as well as the overall reflectance behaviour of metallic surfaces. http://doi.ieeecomputersociety.org/10.1109/MCG.2011.110 http://doi.ieeecomputersociety.org/10.1109/MCG.2011.109 During the last decade, several techniques have been developed for transplanting motions. Here, a partial auxiliary motion, possibly defined for a small set of degrees of freedom, is transplanted on a base motion. Motion transplantation improves the expressiveness of motion databases and allows more control in interactive applications as various body parts can be synthesized separately. However, the auxiliary motion needs to properly aligned with the base motion, both temporally and spatially. In this paper, we provide an overview of example-based motion transplantation techniques and elaborate on how they determine a spatial and temporal alignment between the auxiliary and base motion. Furthermore, we will elaborate on hybrid techniques that are able to transplant resulting motions from procedural or physics-based techniques. http://doi.ieeecomputersociety.org/10.1109/MCG.2011.109 http://doi.ieeecomputersociety.org/10.1109/MCG.2011.107 Human-made constructions appearance is very dependent on various aging phenomena, resulting in complex patterns that vary with time and environment. Handling such complexity is important in computer graphics in order to improve the realism of virtual scenes. Artists often do this difficult work by hand. Their results are often very good, at the price of two main problems that need to be solved. First, designing specific aging patterns is a tedious task. Also, a large amount of bibliographical work, in various scientific fields, is needed to put these patterns in the correct locations on damaged objects, to obtain plausible results. Another way to tackle this problem is to provide new aging algorithms. In this paper, we address salt-based aging, which leads to very rich and common changes in appearance, and plays an important part in the realism of scenes featuring stone structures and monuments. Our model is physically-inspired: it is based on physical behaviors and principles. It leads to plausible results, replacing the simulation of complex physical formulations by ad-hoc algorithms. An important purpose is to help designers locate aging patterns on affected objects. http://doi.ieeecomputersociety.org/10.1109/MCG.2011.107 http://doi.ieeecomputersociety.org/10.1109/MCG.2011.106 Abstract—We present a new algorithm for the interactive rendering of complex lighting effects inside heterogeneous materials. Our approach combines accurate tracing of light rays in heterogeneous refractive media to compute high frequency phenomena, with a lattice-Boltzmann method to account for low-frequency multiple scattering effects. The presented technique is designed for parallel execution of these two algorithms on modern graphics hardware. http://doi.ieeecomputersociety.org/10.1109/MCG.2011.106 http://doi.ieeecomputersociety.org/10.1109/MCG.2011.105 We present a highly realistic visualization of the surface material of living brain tissue. Our goal is to improve the appearance of internal anatomy models used for education and training purposes, and our initial experiments have focussed on the human brain. Traditional teaching aids include images in text books, cadaveric dissection (where the appearance of tissues is quite different from when the tissue was still alive), plastic models (that are far from visually realistic) and computer generated models from medical images (which are mostly grey scale or use pseudo colours). In this case study we have been granted access to both an operating theatre during a neurosurgical procedure, and a dissection room at a medical school. The parameters required for a bidirectional reflectance distribution function (BRDF) are obtained and then used in the rendering process. Visualization of the brain’s surface is achieved in realtime by utilizing the GPU, and includes support for ambient occlusion, advanced texturing, sub surface scattering and specularity. http://doi.ieeecomputersociety.org/10.1109/MCG.2011.105 http://doi.ieeecomputersociety.org/10.1109/MCG.2011.87 Relatively few algorithms take collective group features such as group formations into consideration when simulating a crowd. Recent approaches often manually specify hard constraints such as pre-defined key-frame agent formations and interpolate them during the simulation. We propose an interactive and scalable framework to generate freestyle group formations and transitions via natural and flexible sketching user interactions. Our group formation generation algorithm can automatically compute a plausible agent distribution in the target formation and agent correspondences between key-frames. On the other hand, our introduced two-level formation trajectory control scheme is able to guide the agents' moving/transition paths from an initial formation to the target formation with intuitive user control. Through numerous crowd simulation experiments, we found that our proposed framework is capable of efficiently generating various freestyle group formations in a crowd on-the-fly, while providing sufficiently flexible control to users. http://doi.ieeecomputersociety.org/10.1109/MCG.2011.87 http://doi.ieeecomputersociety.org/10.1109/MCG.2011.85 This paper presents a system for assisting the user to create a 3D model easily and quickly from a single image. Our scene model is composed of a background and foreground objects whose coordinates are calculated based on a “boundary” between “ground” and “wall”. Moreover, we introduce a fast method for extracting a foreground object by combining image segmentation and graph cut-based optimization. We show that the proposed system enables efficient modeling of foreground objects, easy creation of their textures, and rapid construction of a 3D scene model that is simple but produces sufficient 3D effects. http://doi.ieeecomputersociety.org/10.1109/MCG.2011.85 http://doi.ieeecomputersociety.org/10.1109/MCG.2011.51 Marbling is the art of creating stone-like or intricate abstract decorations from liquid inks floating on water or gel. Although the fluid dynamics of marbling processes can be simulated, we introduce a mathematical approach with closed-form expressions. Our approach improves control, ease of implementation, parallelism, and speed, which enables real-time visual feedback as well as the creation of vivid flowing animations. Designs can be started from a blank sheet or raster images and videos. When started from a blank sheet, our approach can produce compact resolution-independent vector outputs. The transforms for our marbling operations all have inverse transforms. Forward application is used to generate compact resolution-independent vector-based output; inverse application is used to generate pixel-based output. In both cases, the closed-form expressions preserve the quality and sharpness of the designs. The efficiency and effectiveness of our method are demonstrated via extensive comparisons with existing digital marbling techniques. We also show various applications including cyclic texture tiling, scene decoration, surface detail rendering for 3D objects, image editing, and interactive video processing. http://doi.ieeecomputersociety.org/10.1109/MCG.2011.51 http://doi.ieeecomputersociety.org/10.1109/MCG.2011.49 OCME (Out-of-Core Mesh Editing) is a novel data-structure and related algorithms for out-of-core editing of large meshes. OCME uses a hashed multigrid where the triangles are inserted on the base of their size and position. This choice allows a rapid access and, on average, a constant construction time per triangle. Unlike previous approaches, no explicit hierarchy is maintained and therefore insertion/modification/deletion of data does not require costly refitting procedures. OCME stores attributes locally, for example it allows to assign vertex color only to a small subparts of the dataset, and naturally handles multiple-scale datasets. http://doi.ieeecomputersociety.org/10.1109/MCG.2011.49 http://doi.ieeecomputersociety.org/10.1109/MCG.2011.14 Unorganized point clouds obtained from 3D shape acquisition devices usually present noises, outliers, and non-uniformities. In this article, we propose a framework to consolidate unorganized points by an iterative procedure of interlaced down-sampling and up-sampling steps. After down-sampling and up-sampling, selection operations are conducted to remove outliers while preserving geometric details. The uniformity of points is improved by moving the down-sampled particles and the following refinement of point samples, and the missed regions are filled through surface extrapolation. Moreover, an adaptive sampling strategy is employed to speed up the iterations. Experimental results demonstrate the effectiveness of the proposed point processing framework. http://doi.ieeecomputersociety.org/10.1109/MCG.2011.14 http://doi.ieeecomputersociety.org/10.1109/MCG.2010.106 Sketch-n-Stretch is a sketching system for novice users to create 2D animations quickly, using a seamless two-layer drawing interface that supports cutouts within a ‘whiteboard’ metaphor. Animated cutouts serve as building blocks to help users to construct quite sophisticated animations easily. Users can draw and write text, while manipulating animated cutouts to create effects which have been difficult with previous sketching approaches, such as articulated figures, multiple motions, and image objects. Sketch-n-Stretch has an intuitive timeline interface with visually integrated motion cues, and supports several traditional animation effects. Novice users evaluated the effectiveness of Sketch-n-Stretch in creating object motions, in comparison with an existing sketching tool, with positive results. They also used Sketch-n-Stretch to animate complete stories, fully utilizing its advanced features. http://doi.ieeecomputersociety.org/10.1109/MCG.2010.106 http://doi.ieeecomputersociety.org/10.1109/MCG.2010.104 Up to now, there was a disassociation between the rules and their application, resulting in a somewhat unnatural development process. We provide a direct visual rulebase editing metaphor, which intuitively lets artists create buildings without changing their workflow. This is based both on a key realization, that the rulebase actually represents a directed acyclic graph (DAG), and on a shift in the development paradigm from a product-based representation to a rule-based one. This allows the user to visually add or edit new rules, connect them controlling the workflow, and easily create new commands that expand the artist toolbox (e.g. boolean operations or local controlling operators). This also opens new possibilities, from model verifications to model editing through graph rewriting operations. http://doi.ieeecomputersociety.org/10.1109/MCG.2010.104 http://doi.ieeecomputersociety.org/10.1109/MCG.2010.99 Non-rigid deformation is a fundamental feature in face recognition. In this paper, a novel approach is proposed to address the issue of non-rigid deformation extraction by finding the mapping between two shapes. A combination scheme which integrates geometric shape decomposition and non-rigid point set registration is proposed to improve registration accuracy. Based on manifold harmonics, shapes are first decomposed into low-frequency and high-frequency parts. Then the modified registration algorithm is applied to obtain deformation parameters. We have conducted an extensive set of experiments to evaluate the performance on FRGC v2 database, from which the promising results show that the proposed algorithm not only performs better fitting accuracy, but also achieves 98.2% identification rate and 97.4% verification rate at 0.001 FAR. http://doi.ieeecomputersociety.org/10.1109/MCG.2010.99 http://doi.ieeecomputersociety.org/10.1109/MCG.2010.67 High-fidelity interactive rendering has been traditionally restricted, to expensive shared memory or dedicated distributed processors, due to the high computational cost. A desktop grid offers a low cost alternative by combining arbitrary computational resources connected to a network such as those in a laboratory or an office. However, prevalent interactive rendering algorithms are currently incapable of seamlessly handling the variable computational power offered by the non-dedicated resources of a desktop grid. In this article, we present a novel fault-tolerant algorithm for rendering high-fidelity images at an interactive rate which is capable of handling variable resources. A conventional approach of rescheduling failed jobs in a volatile environment would inhibit performance while rendering at interactive rates as the time margins are small. Instead, our method uses quasi-random sampling along with image reconstruction techniques to deal with faults. This enables users to experience interactive high-fidelity rendering on their desktop machines. http://doi.ieeecomputersociety.org/10.1109/MCG.2010.67