Shadow geometry maps for alias-free shadows

Shadow maps sample scene visibility in the light source space and offer an efficient solution to generate hard shadows.However,they suffer from aliasing artifacts because of discretization errors,inadequate resolution and projection distortion.In this paper,we propose the shadow geometry map method,where a shadow depth map is augmented by storing geometry information about scenes.This leads to a new shadowrendering algorithm that combines a supersampling filter,a geometry-aware reconstruction kernel and an irregular sampling filter.Our method produces high quality alias-free and subpixel supersampling shadow rendering and retains the simplicity and the efficiency of shadow maps.We show that the algorithm pipeline is efficiently parallelized using current programmable graphics hardware and that our method is capable of generating high quality hard shadows.     

一种基于鲁棒局部纹理特征的背景差分方法

针对复杂场景下运动目标的精确检测这一问题,提出一种对噪声鲁棒并具备灰度尺度不变性的局部纹理特征描述子LBP_Center,将其与像素的颜色信息结合应用于背景建模中,采用随机抽样的机制更新模型,同时引入背景复杂度以去除多模态动态背景产生的噪点。在标准测试数据集上的实验结果表明,该算法对柔性阴影及光照缓慢变化具备良好的鲁棒性,综合性能更优。     

基于Morfit 3D引擎的三维游戏开发研究

基于游戏引擎开发三维游戏是目前游戏开发的潮流。3D游戏开发引擎封装了复杂的底层3D API编程细节，这将大大地减少开发的难度和开发时间。Morfit 3D引擎以其强大的工具集合、3D图形函数，使程序员能在几个星期内编写出功能强大、娱乐性较高、具有艺术级的画面质量的游戏。文中以3D游戏的实现技术为主题，介绍了基于Morfit 3D游戏开发引擎、WIN32 GDI以及Visual C＋＋ 6．0集成开发环境开发第一人称射击类游戏的过程，详细介绍了光影渲染、动画系统、物理系统、渲染系统、交互系统的实现等关键技术。     

基于阴影映射的实时软阴影算法及实现

提出了一种利用阴影映射技术的实时软阴影生成算法。该算法首先生成阴影映射图,然后将阴影区域渲染到定点纹理中,并使用高斯滤波对其进行模糊处理,最后将模糊后的纹理投射回屏幕空间。实验表明,该算法对较复杂物体在保证良好的绘制视觉效果的同时,能达到令人满意的帧速率,从而为大规模复杂场景的实时阴影生成提供了有效的解决途径。     

A Survey of Real‐Time Hard Shadow Mapping Methods

Because of its versatility, speed and robustness, shadow mapping has always been a popular algorithm for fast hard shadow generation since its introduction in 1978, first for offline film productions and later increasingly so in real‐time graphics. So it is not surprising that recent years have seen an explosion in the number of shadow map related publications. Because of the abundance of articles on the topic, it has become very hard for practitioners and researchers to select a suitable shadow algorithm, and therefore many applications miss out on the latest high‐quality shadow generation approaches. The goal of this survey is to rectify this situation by providing a detailed overview of this field. We show a detailed analysis of shadow mapping errors and derive a comprehensive classification of the existing methods. We discuss the most influential algorithms, consider their benefits and shortcomings and thereby provide the readers with the means to choose the shadow algorithm best suited to their needs.     

一种基于视觉的交通检测方法

在实际交通图像检测中检测系统要面对照度变化、局部遮挡和道路阴影等问题，针对这些问题提出一种基于视觉的检测方法，实验表明新方法对解决上述问题的有效性，并在计算车辆数量和速度方面有较高的精确度和较快的执行速度。     

Adaptive mesh generation for progressive radiosity: A ray-tracing based algorithm.

The radiosity method is one of the most popular rendering algorithms. It allows to simulate interreflections of light accurately between surfaces as energy transfers are well designed. However, this algorithm and its derivatives need to break scenes into a relatively large number of small elements to approximate the illumination function. Even with a very large number of elements, not all the illumination effects can be simulated. In fact, there are always artefacts when modelling sharp shadows, besides shadows falling between mesh vertices can be missed entirely. To reduce the computational cost of such methods and to increase the accuracy of the radiosity solution, adaptive mesh generation is well suited. In this paper, we present a ray-tracing based algorithm for adaptive mesh generation which resolves all the illumination problems without lengthening computation time too much. This method allows a small number of initial elements and increases element density in critical locations while solving the illumination problem.     

Building as Refined Object: The Architecture of Antonio Citterio

Sebastiano Brandolini describes the work of Antonio Citterio who, despite a low-key personal presence on the Italian architectural scene and an architecture of quiet restraint, has gained an enviable international reputation for his elegant and ‘impeccably well-made’ buildings. Copyright © 2007 John Wiley & Sons, Ltd.     

基于激光雷达数据阴影处理和图像融合的地物分类方法

城市可见光图像中高大的建筑和树木造成的阴影及部分树木区域出现的颜色失真问题使得传统的颜色量化方法不能准确描述地物谱差异,最终导致分类精度下降。针对可见光图像中的阴影和颜色失真问题提出了一种改进办法:第一阶段针对阴影导致的被掩盖区域谱信息缺失问题,对阴影区域进行采样、分析,通过双阈值提取阴影区域并以面向对象分类方法获得绿色区域阴影。第二阶段通过融合树木区域在多源信息[激光雷达强度、多次回波的数字表面模型(DSM)]中的差异特征,剔除冗余,获取准确的树木区域,弥补颜色失真使得树木区域提取不完全的缺陷。实验结果与人工获取的真实数据对比显示,该方法与传统的Dempster-Shafer(D-S)证据理论融合方法相比,分类精度有了明显的提高。     

Shading with Curve Light Sources1

A new shading model for curve light sources is presented. It accounts for both diffuse reflection and specular reflection of the illuminated surface. By regarding a linear light source as a directional quadrilateral light source with very small width, a simple formula is derived first for calculating the diffuse reflection component due to the illumination of the linear segment. The diffuse reflection of the surface by direct illumination of a curve light source is then evaluated by approximating the curve light with a series of linear segments. The specular reflection component due to a curve light source is represented by an integration taking Phong's specular model as the kernel and evaluated by summing the contributions from the linear segments. Finally, an efficient shadow detection algorithm for curve light sources is proposed. The images rendered with the shading model are very photo-realistic.