GPU-based rendering for deformable translucent objects

In this paper we introduce an approximate image-space approach for real-time rendering of deformable translucent models by flattening the geometry and lighting information of objects into textures to calculate multi-scattering in texture spaces. We decompose the process into two stages, called the gathering and scattering corresponding to the computations for incident and exident irradiance respectively. We derive a simplified illumination model for the gathering of the incident irradiance, which is amenable for deformable models using two auxiliary textures. In the scattering stage, we adopt two modes for efficient accomplishment of the view-dependent scattering. Our approach is implemented by fully exploiting the capabilities of graphics processing units (GPUs). It achieves visually plausible results and real-time frame rates for deformable models on commodity desktop PCs.     

Haptic two-finger contact with textiles

Real-time cloth simulation involves many computational challenges to be solved, particularly in the context of haptic applications, where high frame rates are necessary for obtaining a satisfying experience. In this paper, we present an interactive cloth simulation system that offers a compromise between a realistic physics-based simulation of fabrics and a haptic application meeting high requirements in terms of computation speed. Our system allows the user to interact with the fabric using two fingers. The required performance of the system is achieved by introducing an intermediate layer responsible for the simulation of the small part of the surface being in contact with the fingers. Additionally we separate the possible contact situations into different cases, each being individually handled by a specialised contact algorithm.

Optimization of clamped circular piezoelectric composite actuators

This paper addresses the design of clamped circular piezoceramic composite unimorph and bimorph configurations, specifically the conflicting requirements of maximum volume displacement for a prescribed bandwidth. An optimization problem is formulated that implements analytical solutions for unimorph and bimorph configurations using laminated plate theory, including the use of oppositely polarized piezoceramic patches. A range of actuator geometric parameters are studied, and bounds for volume displacement and natural frequency of optimal designs are determined and presented via design curves. In the selected design space, Pareto optimization results for unimorph and bimorph configurations show that optimal volume displacement is related to the bandwidth by a universal power law such that the product of the square of the natural frequency and the displaced volume, a “gain-bandwidth” product, is a constant. Characteristic trends are also described that are independent of the actuator radius for the Pareto optimal piezoceramic patch thickness and radius versus normalized bandwidth. The results are relevant, for example, in the design of zero-net mass-flux or synthetic jet actuators used in flow control applications.     

直接体绘制技术研究

直接体绘制技术是可视化研究领域的一个重要分支,是目前最活跃的可视化技术之一。该文首先介绍了体绘制技术的原理,分析其实现的关键技术及算法。然后介绍了可视化工具VTK,及其对光线投射算法的实现过程。     

视频图像在三维模型中的渲染

视频监控是大型安防工作中最重要的一个环节,传统的视频监控系统展示给用户的只是独立的二维平面图像,图像脱离环境,整体性不足,为了解决该问题,提出了将视频图像渲染显示于三维模型的思路.研究了纹理映射技术并结合视频图像渲染的特殊性分析研究了Z缓冲算法、Shadow map算法,根据实际应用提出Extend Shadow map算法以实现将视频图像与三维场景无缝贴合.实验结果表明,视频图像渲染显示于三维模型中所体现的优越性.     

Extreme simplification and rendering of point sets using algebraic multigrid

We present a novel approach for extreme simplification of point set models, in the context of real-time rendering. Point sets are often rendered using simple point primitives, such as oriented discs. However, this requires using many primitives to render even moderately simple shapes. Often, one wishes to render a simplified model using only a few primitives, thus trading accuracy for simplicity. For this goal, we propose a more complex primitive, called a splat, that is able to approximate larger and more complex surface areas than oriented discs. We construct our primitive by decomposing the model into quasi-flat regions, using an efficient algebraic multigrid algorithm. Next, we encode these regions into splats implemented as planar support polygons textured with color and transparency information and render the splats using a special blending algorithm. Our approach combines the advantages of mesh-less point-based techniques with traditional polygon-based techniques. We demonstrate our method on various models.     

计算机时代的设计效果图渲染新说

手工绘图时期非常注重各种绘图工具的学习,计算机的出现使得手工绘图工具对效果图的渲染变的不再重要。要想画好效果图,提高人脑的认识才是关键。本文从实践设计总结的经验出发,提出效果图渲染的学习,从认识上可以分为"全因素表现"和"快速表现";进一步又阐述了每种渲染在设计师的头脑认识上需要把握哪好些处理内容。     

Recent elevation changes of Svalbard glaciers derived from ICESat laser altimetry

We have tested three methods for estimating 2003-2008 elevation changes of Svalbard glaciers from multi-temporal ICESat laser altimetry: (a) linear interpolation of crossover points between ascending and descending tracks, (b) projection of near repeat-tracks onto common locations using Digital Elevation Models (DEMs), and (c) least-squares fitting of rigid planes to segments of repeat-track data assuming a constant elevation change rate. The two repeat-track methods yield similar results and compare well to the more accurate, but sparsely sampled, crossover points. Most glacier regions in Svalbard have experienced low-elevation thinning combined with high-elevation balance or thickening during 2003-2008. The geodetic mass balance (excluding calving front retreat or advance) of Svalbard's 34,600 km² glaciers is estimated to be −4.3 ± 1.4 Gt y⁻¹, corresponding to an area-averaged water equivalent (w.e.) balance of −0.12 ± 0.04 m w.e. y⁻¹. The largest ice losses have occurred in the west and south, while northeastern Spitsbergen and the Austfonna ice cap have gained mass. Winter and summer elevation changes derived from the same methods indicate that the spatial gradient in mass balance is mainly due to a larger summer season thinning in the west and the south than in the northeast. Our findings are consistent with in-situ mass balance measurements from the same period, confirming that repeat-track satellite altimetry can be a valuable tool for monitoring short term elevation changes of Arctic glaciers.     

Improving content visibility for high‐ambient‐illumination viewable display and energy‐saving display

Abstract— Nowadays, low‐contrast viewing of LC displays (LCDs) occurs very often, which includes the viewing of mobile LCDs at high ambient illumination and the viewing of LCDs at low‐power mode. These cases result in low‐content visibility and low contrast, leading to an unpleasant viewing experience. In this paper, a technique to improve the perceived contrast and visibility of images at low‐contrast viewing conditions is proposed. The proposed approach enhances image brightness with content and ambient adaptive image brightening and highlights visual parts and boundaries with non‐photorealistic rendering. The proposed technique enables longer battery life for mobile LC devices and makes mobile LC devices viewable at high ambient illumination. It also enables TVs with extreme low‐power consumption and smart‐grid responsive TVs.     

Computing integrals over polynomially defined regions and their boundaries in 2 and 3 dimensions

We use the cylindrical algebraic decomposition algorithms implemented in Mathematica to produce procedures to analytically compute integrals over polynomially defined regions and their boundaries in two and three dimensions. Using these results, we can implement the divergence theorem in three dimensions or the Green's theorems in two dimensions. These theorems are of central importance in the applications of multidimensional integration. They also provide a strong correctness test for the implementation of our results in a computer algebra system. The resulting software can solve many of the two and some of the three dimensional integration problems in vector calculus textbooks. The three dimensional results are being extended. The results in this paper are being included in an automated student assistant for vector calculus.