Recent Advances In Computer Graphics Research Articles

Path integrals formulations leading to propagator evaluation for coupled linear physics in large geometric models

Reformulating linear physics using second kind Fredholm equations is very standard practice. One of the straightforward consequences is that the resulting integrals can be expanded (when the Neumann expansion converges) and probabilized, leading to path statistics and Monte Carlo estimations. An essential feature of these algorithms is that they also allow to estimate propagators for all types of sources, including initial conditions. The resulting practice is a single Monte Carlo run, for one given set of sources, producing propagators that can later be used with any other set of sources for fast simulations, typically as parts of optimization, inversion, sensitivity analysis and command control algorithms. The present paper illustrates how this practice can be extended to problems involving several interacting physics, provided that their coupling is only at the boundary of the system or at interfaces between sub-parts, and may itself be given the form of a second kind Fredholm equation. A full practical implementation is described as part of the Stardis code, with the example of transferring heat via the coupling of radiation, reaction-diffusion and convection as typically expected in the multidisciplinary context of urban climate modeling. Besides, we show how recent advances in computer graphics indicate that these algorithms can be made numerically extremely efficient when facing large CAD geometries: computing the propagator becomes strictly independent of the geometry refinement, i.e. is identical whatever the number of triangles and tetraedra used to numerize the surface and volume descriptions. To the best of our knowledge this is the first report of propagator computations that remains practical for coupled physics in large CAD geometries. Program summaryProgram Title: Stardis 0.7.2 (built on stardis-solver 0.12.3)CPC Library link to program files:https://doi.org/10.17632/k76zrx4n6b.1Developer's repository link:https://www.meso-star.com/projects/stardis/stardis.htmlLicensing provisions: GPLv3Programming language: ANSI C and PythonNature of problem: Estimating temperatures in coupled heat transfer systems involving large CAD and/or large numbers of spatially distributed sources.Solution method: Stardis uses the Monte Carlo Method. Each temperature estimate constructs a propagator of each of the energy sources within the system: initial temperature, temperature boundary conditions, volume powers and surface fluxes. The propagator can be stored for further use outside the Monte Carlo code.Additional comments including restrictions and unusual features: The Stardis estimates of propagators are only reliable when radiative transfer can be linearized around a reference temperature. Stardis can deal with the nonlinearity of radiation when computing temperatures, but then nothing can be interpreted as a meaningfull propagator for any external usage.Python scripts were used to execute the different configurations, post-process the results and generate the different graphs.

Remote Sensing Novel View Synthesis With Implicit Multiplane Representations

Novel view synthesis of remote sensing scenes is of great significance for scene visualization, human-computer interaction, and various downstream applications. Despite the recent advances in computer graphics and photogrammetry technology, generating novel views is still challenging particularly for remote sensing images due to its high complexity, view sparsity and limited view-perspective variations. In this paper, we propose a novel remote sensing view synthesis method by leveraging the recent advances in implicit neural representations. Considering the overhead and far depth imaging of remote sensing images, we represent the 3D space by combining implicit multiplane images (MPI) representation and deep neural networks. The 3D scene is reconstructed under a self-supervised optimization paradigm through a differentiable multiplane renderer with multi-view input constraints. Images from any novel views thus can be freely rendered on the basis of the reconstructed model. As a by-product, the depth maps corresponding to the given viewpoint can be generated along with the rendering output. We refer to our method as Implicit Multiplane Images (ImMPI). To further improve the view synthesis under sparse-view inputs, we explore the learning-based initialization of remote sensing 3D scenes and proposed a neural network based Prior extractor to accelerate the optimization process. In addition, we propose a new dataset for remote sensing novel view synthesis with multi-view real-world google earth images. Extensive experiments demonstrate the superiority of the ImMPI over previous state-of-the-art methods in terms of reconstruction accuracy, visual fidelity, and time efficiency. Ablation experiments also suggest the effectiveness of our methodology design. Our dataset and code can be found at https://github.com/wyc-Chang/ImMPI

A Curriculum Domain Adaptation Approach to the Semantic Segmentation of Urban Scenes.

During the last half decade, convolutional neural networks (CNNs) have triumphed over semantic segmentation, which is one of the core tasks in many applications such as autonomous driving and augmented reality. However, to train CNNs requires a considerable amount of data, which is difficult to collect and laborious to annotate. Recent advances in computer graphics make it possible to train CNNs on photo-realistic synthetic imagery with computer-generated annotations. Despite this, the domain mismatch between real images and the synthetic data hinders the models' performance. Hence, we propose a curriculum-style learning approach to minimizing the domain gap in urban scene semantic segmentation. The curriculum domain adaptation solves easy tasks first to infer necessary properties about the target domain; in particular, the first task is to learn global label distributions over images and local distributions over landmark superpixels. These are easy to estimate because images of urban scenes have strong idiosyncrasies (e.g., the size and spatial relations of buildings, streets, cars, etc.). We then train a segmentation network, while regularizing its predictions in the target domain to follow those inferred properties. In experiments, our method outperforms the baselines on two datasets and three backbone networks. We also report extensive ablation studies about our approach.

A modular virtual reality system for engineering laboratory education

AbstractThe globalization trend has affected the tertiary education sector, resulting in an increased flow of both students and academics across borders. Economic pressures on universities and the emergence of new technologies have spurred the creation of new systems in engineering education. The recent advances in computer graphics have exposed great potential in education at all levels. The Virtual Reality (VR) is a promising technology which aims to assist the students in the visualization of concepts and to provide immediate graphical feedback during the learning process. This article presents a modular interactive teaching package, called Virtual Learning System (VLS), which can be used by people with little prior computer experience. VLS provides a comprehensive and conductive yet dynamic and interactive environment that can be incorporated into various courses in the field of Mechanical and Manufacturing Engineering. The evaluation of the learning process with the developed system has been done through laboratory reports, lab quizzes and questionnaires implemented with a tutorial monitoring application. © 2009 Wiley Periodicals, Inc. Comput Appl Eng Educ 19: 305–314, 2011

Linear affine transformations between 3-lead (Frank XYZ leads) vectorcardiogram and 12-lead electrocardiogram signals

Background Recent advances in computer graphics and wireless technologies have renewed interest in vectorcardiogram (VCG) signals that use fewer leads than the conventional 12-lead electrocardiogram (ECG) signals for medical diagnostic applications. However, most cardiologists are accustomed to the 12-lead ECG even though some of the leads are either nearly aligned with or derived from the others and consequently contain redundant information. The ability to transform from orthogonal 3-lead VCG to 12-lead ECG enables the use of fewer leads for signal analysis, computer visualization, and wireless transmission of signals. This can also improve mobility, albeit limited, to the patients. Materials and Methods We present a statistical approach to transform 3-lead Frank VCG to 12-lead ECG signals and vice versa, based on Dower's pioneering work on lead tranformation. This approach enables compensation of baseline shifts and other constant biases present in long ECG data streams, so that the resulting statistical transforms can be more consistent and accurate. We compare the performance of the affine transform with that of Dower transform (from 3 to 12 and from 12 to 3) using the data from the PhysioNet PTB database. Results The results show that for both myocardial infarction (MI) and healthy control (HC) subjects, the statistical affine transform presented here maps 3-lead VCG to12-lead ECG more accurately than Dower or other lead transformation matrices of the ECG recordings. Discussion This investigation also shows the limitations associated with single dipole assumption that underlies Dower's geometric transformation. The results also indicate that lead transformation accuracy can be improved using separate customized transforms to, for example, age or pathologic conditions (here, MI vs HC) than a single statistical or geometric transform. Pertinently, we find that the affine transform coefficients can serve as discriminating features for classification/discrimination of MI patients from HC subjects.

Low-Level Image Cues in the Perception of Translucent Materials

When light strikes a translucent material (such as wax, milk or fruit flesh), it enters the body of the object, scatters and reemerges from the surface. The diffusion of light through translucent materials gives them a characteristic visual softness and glow. What image properties underlie this distinctive appearance? What cues allow us to tell whether a surface is translucent or opaque? Previous work on the perception of semitransparent materials was based on a very restricted physical model of thin filters [Metelli 1970; 1974a,b]. However, recent advances in computer graphics [Jensen et al. 2001; Jensen and Buhler 2002] allow us to efficiently simulate the complex subsurface light transport effects that occur in real translucent objects. Here we use this model to study the perception of translucency, using a combination of psychophysics and image statistics. We find that many of the cues that were traditionally thought to be important for semitransparent filters (e.g., X-junctions) are not relevant for solid translucent objects. We discuss the role of highlights, color, object size, contrast, blur, and lighting direction in the perception of translucency. We argue that the physics of translucency are too complex for the visual system to estimate intrinsic physical parameters by inverse optics. Instead, we suggest that we identify translucent materials by parsing them into key regions and by gathering image statistics from these regions.

A desktop VR prototype for industrial training applications

The recent advances in computer graphics has spurred interest from both academics and industries in virtual reality (VR) enabled training applications. This paper presents a desktop VR prototype for industrial training applications. It is designed and implemented as a general shell by providing the data interface to import both the virtual environment models and specific domain knowledge. The geometric models of the virtual environment are constructed using feature-based modelling and assembly function by external CAD tools, and then transferred into the prototype through a conversion module. A hierarchical structure is proposed to partition and organise these imported virtual environment models. Based on this structure, a visibility culling approach is developed for fast rendering and user interaction. The case study has demonstrated the functionality of the proposed prototype system by applying it to a maintenance training application for a refinery bump system, which, in general, has a large number of polygons and a certain depth complexity. Significant speedup in both context rendering and response to user manipulations has been achieved to provide the user with a fast system response within the desktop virtual environment. Compared with the immersive VR system, the proposed system has offered an affordable and portable training media for industrial applications.

Automating Lighting Design for Interactive Entertainment

Recent advances in computer graphics, particularly in real-time rendering, have resulted in major improvements in 3D graphics and rendering techniques in interactive entertainment. In this article we focus on the scene-lighting process, which we define as configuring the number of lights in a scene, their properties (e.g., range and attenuation), positions, angles, and colors. Lighting design is well known among designers, directors, and visual artists for its vital role in influencing viewers' perception by evoking moods, directing their gaze to important areas (i.e., providing visual focus), and conveying visual tension. It is, however, difficult to set positions, angles, or colors for lights within interactive scenes to accommodate these goals because an interactive scene's spatial and dramatic configuration, including mood, dramatic intensity, and the relative importance of different characters, change unpredictably in real-time. There are several techniques developed by the game industry that establish spectacular real-time lighting effects within 3D interactive environments. These techniques are often time- and labor-intensive. In addition, they are not easily used to dynamically mold the visual design to convey communicative, dramatic, and aesthetic functions as addressed in creative disciplines such as art, film, and theatre. In this article we present a new real-time lighting design model based on cinematic and theatric lighting design theory. The proposed model is designed to automatically, and in real-time, adjust lighting in an interactive scene to accommodate the dramatic, aesthetic, and communicative functions described by traditional lighting design theories, while taking artistic constraints on style, visual continuity, and aesthetic function into account.

Virtual imaging for teaching cardiac embryology.

Knowledge of the embryology of the normal heart is essential for understanding the development of congenital cardiopathies. However, learning embryology is not an easy matter because it requires understanding the intricacy and evolution of many complex structures and functions. Classically, this evolution is usually described in textbooks by means of drawings and sketches. With these techniques, however, it is difficult to imagine the spatial and temporal links. Recent advances in computer graphics have brought about ways to illustrate these dimensions. We developed a …

A Visual Formalism for Computational Tree Logic

The recent advances in computer graphics and multimedia technology provide new means for the visualization of abstract information spaces through the use of multi-dimensional and multi-modal communication channels. In the context of computer-aided verification, this potential can be effectively employed to provide visual notations for mathematical formalisms. We describe a visual system which supports visual presentation and manipulation of temporal sequencing properties expressed in the formalism of computation tree logic. The system enforces a metaphoric transposition of the abstract temporal semantics of the logic onto a concrete visual space through the use of 3D graphics, multiple windowing, color associations, and through the joint and coherent exploitation of both textual and graphic representations. This results in a complex interaction environment supporting syntactic parsing, semantic understanding, and visual editing of temporal expressions.

仮想環境のための干渉力発生アルゴリズム

Graphic simulators are currently used in application such as off-line teaching tasks on industrial robots and CAD systems. While recent advances in computer graphics have led to the development of high powered computers with high quality static and dynamic graphics, the display of kinesthetic information is still lacking. This display of kinesthetic information is critical for the development of simulators that can more accurately and realistically present simulated objects to the user. With this problem in mind, this paper proposes a method of calculating interaction forces produced in the simulation world. These forces are effectively used in a simulator where contact forces are felt by the user through its force-reflecting handle. In this method, two fundamental contacts, Face-Vertex and Edge-Edge, will be introduced, and the interaction force calculations will be defined. It will be demonstrated that every contact between two convex polyhedral objects can be described using this set of the fundamental contacts. The interaction forces will be determined from the sum of forces calculated at each fundamental contact. Using a simulator system which displays forces, certain preliminary experiments are carried out and the effectiveness of the method confirmed.

A film recording and image processing system for confocal microscopy

Scanning confocal microscopy has developed into a very useful technique for many scientific investigations. However, commercial development has been so rapid that some recent advances in computer graphics and imaging have not been incorporated into the commercial systems. One particular concern was high quality hard copy with alpha-numeric and graphic overlays. A subsystem was developed to provide this output for the BioRad MRC-500/600 confocal imaging system.A digital film recorder, an Agfa Matrix Procolor was chosen as the principal element of hardware. This compact unit can record an image at a resolution of 4096 horizontal by 3072 vertical pixels at a cost equivalent to popular analog video film recorders. The interface is a standard IEEE 488 GPIB board. It is compatible with various film emulsions such as Kodak Ecktachrome 100 as well as many of the major graphics arts and image processing programs. The second element of hardware in this system is an ATVista 4M image processing board.

Colour graphics and three-dimensional scene synthesis in image display

Recent advances in computer graphics have allowed the synthesis of realistic scenes consisting of surfaces and their coverings. This can be exploited in image displays, which provide a powerful way of gaining an appreciation of the spatial nature of scientific data. If data variables are represented by the naturally observed properties of realistic scenes, a better appreciation of the data can be attained. This paper shows how sophisticated colour graphics techniques can be incorporated within an image display system to produce realistic three-dimensional scenes. Examples of coloured surfaces representing geoscientific data are shown, and the value, in a graphics context, of the techniques developed for the display of image data is discussed.

Some Recent Advances in Computer Graphics

Computer graphics, no longer a novelty, is on its way to becoming the preferred interface between humans and computers. Continued advances in the development of graphics algorithms are improving the quality and usefulness of this interface. Decreasing hardware costs have enabled an expansion of graphics into more diverse applications.