基于顶点Shader实现的光照计算技术

真实的光照效果模拟一直是计算机图形学中一个倍受瞩目的课题。鉴于此，在Microsoft visual Studio开发环境下，利用DirectX9．0软件包进行3D开发，结合顶点shader技术编程实现了Direct3D支持的三种灯光（平行光、点光、聚光）的顶点光照效果，并与使用标准图形管线实现的光照效果进行了对比。发现前者可以实现更为灵活且真实的光照效果。     

Direct3D中的三维坐标变换

本文简介Direct3D中的顶点变换和光照流水线,并通过具体范例阐述世界变换、观察变换、投影变换和视区变换.     

真实感3D重建中的纹理映射技术

精确的纹理映射是体现模型视觉真实感的关键因素。本文在阐述纹理映射技术原理的基础上,探讨了基于3维激光扫描设备进行3D重建过程中,实现具有高度真实感的纹理映射所遇到的实际问题,提出了基于纹理的模型重构和纹理光照连续性重建算法,解决了纹理图像空间不连续、光照不连续等因素对模型真实感的影响,并通过真实数据的实验对算法有效性进行了验证,为大型户外实体的真实感3D重建奠定了技术基础。     

基于图像的光照模型的研究与实现

为了把计算机生成的虚拟物体更好地融入真实场景的实拍照片中，实现光照一致性的效果，提出了一个基于图像的光照模型，它使用光测图作为光源从而实现对场景的照明。在研究基于图像的局部光照模型时，又提出了双向折射率分布函数这一概念，从而简化了局部光照模型的设计。在实现阶段，采用立方体环境映照来表示场景，采用光测图记录环境映照中光辐射的分布信息，从而提高了绘制效率。实验表明，本模型较成功地实现了光照一致性，在增强现实、图像合成等方面具有很大的应用价值。     

基于Direct3D的雾化效果实现

在3D场景中加入雾化效果能增加场景的真实感、纵深感和距离感,创造环境氛围。微软的D irect 3D提供两种类型的雾:顶点雾和像素雾。雾化结果不仅可以用于模拟雾,也能减少远处场景的清晰度。论述了雾化效果的产生原理和属性,给出了一个实现雾化效果的实例,从而反映了真实世界的情况。     

基于图形硬件的辐照度环境纹理图的计算方法

辐照度环境纹理图是绘制任意光照环境下漫反射物体表面的一种有效的方法。为了实现动态光照环境下辐照度环境纹理图的实时绘制,基于当前的通用图形硬件,提出了一种采用顶点着色器快速计算辐照度环境纹理图的方法。该方法从分析球面调和函数入手,首先得出环境贴图的二次多项式表达形式;然后用顶点着色程序对多项式系数和球面调和函数进行加速计算,以快速生成辐照度环境纹理图;最后对于动态光照环境,则通过对环境纹理图的分级细化来加快光照系数的计算,进而实现了动态光照环境下辐照度环境纹理图的重新绘制。实验表明,在动态光照条件下,采用该方法在获取真实感光照效果的同时,其运算速度也能满足交互系统的需求。     

基于3D Max的虚拟校园设计

随着信息技术的快速发展,利用3D建模技术创建虚拟校园场景,实现校园场景的可视化,已经成为了当前各大院校宣传自身的重要手段.3D Max作为当前最主流的3D建模软件,结合3D Max软件从3D模型构建、纹理贴图以及光照效果设计3个方面进行了虚拟校园设计的研究,希望能够为相关工作提供一些简单的参考.     

3D场景渲染的视觉显著性驱动间接光照复用算法

为提高路径追踪渲染3D场景的速度,提出3D场景渲染的视觉显著性驱动间接光照复用算法。首先,根据视觉感知中感兴趣区域显著性高、其他区域显著性低的特点得到场景画面的2D显著性图,该显著性图由图像的颜色信息、边缘信息、深度信息以及运动信息构成。然后,重新渲染高显著性区域的间接光照,而低显著性区域则在满足一定条件的情况下复用上一帧的间接光照,达到加速渲染的目的。实验结果表明：该算法生成画面的全局光照效果真实,在多个实验场景下的渲染速度均有提升,速度最高能达到高质量渲染的5.89倍。     

发音过程中舌头运动的3D可视化方法*

研究中文发音过程中舌头运动的3D可视化问题。根据核磁共振数据构建舌头精细的3D模型,在此基础上,提取舌背表面处3个点的EMA数据为驱动源,利用弹簧网技术真实再现中文发音过程中的舌头运动。为了验证文中建模和舌头运动合成方法的有效性,使用计算机图形学的方法模拟舌头运动的细节效果,并对比其与由语言学家亲自拍摄的“普通话发音器官动作特征”的X光影像。实验表明,文中方法实现的3D舌头运动符合真实的舌头运动情况,拥有广泛的应用前景。     

基于shader实现的光线透射效果

真实的模拟光线的透射效果是实时计算机图形学中一个非常令人关注的内容.对于这种自然现象的模拟所要达到的两个目标是真实性和实时性.为了达到这一要求,介绍了一种能够实时并且真实的模拟这种自然现象的算法,在Microsoft Visual Studio开发环境下,利用DirectX9.0软件包进行3D开发,并结合shader技术编程实现,运行的结果表明此算法是可行的和高效的.     

基于球面调和函数的漫反射表面快速光照技术的研究

基于图像的光照是计算机图形学中一个新的研究领域。本文研究了一种基于球面调和函数理论的快速光照技术,此方法采用三阶球面调和函数近似估计理想漫反射物体表面的光亮度,以此实现物体表面光亮度的计算。实验结果表明,本算法能够实现真实感图像的实时绘制。     

The irradiance volume

A major goal in computer graphics is realistic image synthesis. To this end, illumination methods have evolved from simple local shading models to physically based global illumination algorithms. Local illumination methods consider only the light energy transfer between an emitter and a surface (direct lighting), while global methods account for light energy interactions between all surfaces in an environment, considering both direct and indirect lighting. Even though the realistic effects that global illumination algorithms provide are frequently desirable, the computational expense of these methods is too great for many applications. Dynamic environments and scenes containing a very large number of surfaces often pose problems for global illumination methods. This article presents a different approach to calculating the global illumination of objects. Instead of striving for accuracy at the expense of performance, we rephrase the goal: to achieve a reasonable approximation with high performance. This places global illumination effects within reach of many applications in which visual appearance is more important than absolute numerical accuracy     

Light Transport in Realistic Rendering: State-of-the-Art Simulation Methods

Programming and Computer Software - The modern realistic computer graphics is based on physically correct lighting simulation. One of the main and computationally difficult problems is the...     

基于生成对抗模型及光路分解的全局光照绘制

针对现有全局光照图像重建高频特征效果模糊的问题,提出一种基于生成对抗模型及光路分解的全局光照绘制网络,以各类图形辅助属性（法线、深度、粗糙度等）为主要输入,学习光照传输的抽象表示并编码,用于推理光照图像。第一,将光照解耦为漫反射和镜面反射两部分,设计独立的生成对抗网络端到端地学习和推理光照子图,避免混频光照的相互干扰,保证高频细节的清晰重现。第二,使用自编码器作为绘制网络的基本结构,添加多尺度特征融合模块用于不同感受野下的特征合成,以促进阴影、镜面反射等复杂特效的有效表达。第三,使用旋转损失和特征损失两种增强的对抗损失函数,增加网络训练的稳定性。实验结果表明,与现有降噪或图像生成模型相比,该方法能够有效地生成视觉上更逼真的全局光照图像,保留更多高频细节,PSNR指标提升8%～20%。     

Speeding up global illumination computations using programmable GPUs

In the context of realistic image synthesis, many stochastic methods have been proposed to sample direct and indirect radiance. We present new ways to use hardware graphics to sample direct and indirect lighting in a scene. Jittered sampling of light sources can easily be implemented on a fragment program to obtain soft shadow samples. Using a voxel representation of the scene, indirect illumination can be computed using hemispherical jittered sampling. These algorithms have been implemented in our rendering framework but can be used in other contexts like radiosity or final gathering of the photon map.     

搪瓷产品造型设计中的真实感图形处理技术

实时性和真实性是真实感图形生成追求的两大目标，本文结合搪瓷产品和微机的特点分别介绍了物体材质效应的表示，用投影区域缓冲器和光源球面缓冲器来加快真实感图形生成及改进的花纹图案映射等方法，把这些方法运用到搪瓷产品的真实感图形生成中，图形生成速度较快，真实感较强。     

Photorealistic rendering of mixed reality scenes

Photo‐realistic rendering of virtual objects into real scenes is one of the most important research problems in computer graphics. Methods for capture and rendering of mixed reality scenes are driven by a large number of applications, ranging from augmented reality to visual effects and product visualization. Recent developments in computer graphics, computer vision, and imaging technology have enabled a wide range of new mixed reality techniques including methods for advanced image based lighting, capturing spatially varying lighting conditions, and algorithms for seamlessly rendering virtual objects directly into photographs without explicit measurements of the scene lighting. This report gives an overview of the state‐of‐the‐art in this field, and presents a categorization and comparison of current methods. Our in‐depth survey provides a tool for understanding the advantages and disadvantages of each method, and gives an overview of which technique is best suited to a specific problem.     

Approximating global illumination on mesostructure surfaces with height gradient maps

Rendering global illumination for objects with mesostructure surfaces is a time-consuming task, and cannot presently be applied to interactive graphics. This paper presents a real-time rendering method based on a mesostructure height gradient map (MHGM) to exhibit lighting effects on meso-scale details in dynamic environments. We approximate global illumination using a lighting model including three components: incident ambient light, direct light and single bounce indirect light. MHGM is introduced to create local apex sets, which would help us to compute the three components adaptively. Our approach runs entirely on the graphics hardware, and uses deferred shading and the graphics pipeline to accelerate computation. We achieve high quality results which can render meso-scale details with approximate global illumination even for low-resolution geometric models. Moreover, our approach fully supports dynamic scenes and deformable objects.     

From Faces to Outdoor Light Probes

Image‐based lighting has allowed the creation of photo‐realistic computer‐generated content. However, it requires the accurate capture of the illumination conditions, a task neither easy nor intuitive, especially to the average digital photography enthusiast. This paper presents an approach to directly estimate an HDR light probe from a single LDR photograph, shot outdoors with a consumer camera, without specialized calibration targets or equipment. Our insight is to use a person's face as an outdoor light probe. To estimate HDR light probes from LDR faces we use an inverse rendering approach which employs data‐driven priors to guide the estimation of realistic, HDR lighting. We build compact, realistic representations of outdoor lighting both parametrically and in a data‐driven way, by training a deep convolutional autoencoder on a large dataset of HDR sky environment maps. Our approach can recover high‐frequency, extremely high dynamic range lighting environments. For quantitative evaluation of lighting estimation accuracy and relighting accuracy, we also contribute a new database of face photographs with corresponding HDR light probes. We show that relighting objects with HDR light probes estimated by our method yields realistic results in a wide variety of settings.