镜头重影效果的真实感绘制

针对现有镜头重影效果绘制方法存在的光线追踪效率低和绘制效果差的问题,提出一种基于物理的真实感镜头重影效果绘制方法.该方法以精确的相机镜头模型为基础,首先计算镜头入射光瞳的位置和孔径,并利用入射光瞳进行初始光线采样来减少无效光线数量,提高光线追踪效率;其次采用确定序列光谱光线追踪方法绘制重影的色差,并考虑了孔径光阑形状、镜头镀膜以及镜头遮挡对镜头重影的影响;最后将镜头重影绘制与光线追踪绘制框架融合,构成镜头重影场景绘制的统一框架,并在三维场景中实现了镜头重影效果的绘制.实验结果表明,文中方法能够有效地模拟具有较强真实感的镜头重影效果.     

基于Navarro示意眼模型的视觉真实感绘制*

结合人眼光学建模和计算机图形学的真实感绘制技术,提出一种基于Navarro示意眼模型的人眼视觉真实感绘制方法.利用Navarro模型与传统的单透镜模型相比能够更精确地模拟人眼的特性,将Navarro模型引入视觉真实感绘制中;采用光线追踪方法,加入非球面折射面的计算,精确地模拟人眼的成像特性.实验结果表明此种方法能够更精...     

真实感眩光效果实时绘制

针对现有眩光效果绘制方法的真实感和速度问题,提出一种基于GPU的真实感眩光效果绘制方法.首先根据光圈和镜头生成带有随机镜头噪声的二维衍射光栅图像;其次考虑夫琅禾费和菲涅耳2种不同的衍射效果,利用预存算法系数的快速傅里叶变换模拟衍射效果的光学过程,并通过衍射效果的光谱模型实现真实感绘制,同时利用2个独立的一维高斯卷积核加速实现bloom效果;再通过随机小角度旋转和混合操作进行真实感增强;最后采用实时光线跟踪渲染框架,在三维场景中实现了真实感眩光效果的实时绘制.该方法的主要步骤采用CUDA实现,充分利用了GPU强大的并行计算能力并兼顾考虑存储器优化策略.实验结果表明,文中方法绘制结果具有较强的真实感和实时性.     

景深效果绘制技术综述

景深效果能够增强计算机生成图像的真实感,因此关于这类效果的绘制已成为计算机图形学中的重要研究方向。针对景深效果的绘制问题,首先研究和分析各种相机镜头模型的光学成像原理,比较各类镜头模型的特点和模拟景深效果的能力;然后分类总结景深效果绘制的基本原理和典型算法,比较各类景深绘制方法的优缺点。最后指出景深效果绘制技术的应用价值,并展望未来的研究方向。     

应用微表面模型进行衍射效果物理绘制

针对当前光子衍射效果绘制方法的真实感问题,提出应用微表面模型的衍射效果物理绘制方法.该方法融合了现有衍射绘制模型中的特点,并结合特定材质的可变菲涅尔系数来增强衍射效果;通过综合考虑微表面对光子的吸收、遮挡、再反射等交互场景,扩展了高度场微表面的适用范围;引入维格纳分布函数推迟衍射效果,以进一步增强微表面模型;利用蒙特卡罗采样理论求解波动方程积分式以降低计算复杂度,辅以几何光线追踪理论,求取微表面辐射度空间分布;最终以光的波动方程为基础,构建了可应用于光线追踪器的双向反射分布函数衍射光学模型.实验结果表明,该模型能够有效地模拟波的相位与幅值信息,可绘制出较为逼真的衍射效果.     

应用薄膜干涉模型进行蝴蝶彩色效果物理绘制

针对当前蝴蝶彩色效果绘制方法的真实感问题,提出一种应用薄膜干涉模型的真实感绘制方法.首先根据蝴蝶表面脊突结构构造多层薄膜模型;然后利用多层薄膜干涉原理模拟光在薄膜内部的多次反射、透射形成的混合散射特性,其中,菲涅尔公式被引入以解释反射或透射波的幅值变化,微表面散射因子被创造性地引入来模拟蝴蝶粗糙表面的各向异性特性;最后通过全波长光谱建模增强干涉效果,在此基础上还将该算法与光线追踪渲染框架相结合,构建了可应用于光线追踪器的波动双向散射分布函数干涉模型,以精确地模拟光的幅值和相位变动.实验结果表明,该模型能够有效地绘制出较为逼真的蝴蝶彩色效果.     

真实感雨线绘制

雨线的真实感绘制极具挑战性.雨滴在下落过程中会发生快速的震荡,由于光线在其中的反射和折射而具有复杂的光学效果,在人眼和摄像机观察时会产生运动模糊形成雨线.提出一种基于Monte Carlo光线跟踪的方法用于绘制真实感雨线.通过预先对雨滴震荡周期内每个离散时间点的雨滴三角形网格建立加速结构,并利用雨滴运动包围盒与采样光线的相交计算,大大加速了光线与雨滴的相交测试;使用自适应采样技术避免了对图像中每个像素点都使用大的采样数,提高了采样效率,加速了图像的绘制.将本文方法集成于离线绘制器(PBRT)中,生成了具有真实感的雨线图像和雨景动画.实验结果表明,本文方法能真实地模拟雨滴的震荡和光线在雨滴中的多次反射和折射,并能在包含任意类型光源的场景中有效地绘制真实感雨线.     

基于物理的浑浊水体的光照模拟

水体的真实感光照模拟是计算机图形学中的重要研究内容.现有的研究偏重于清澈水体的光照模拟,无法直接用于浑浊水体,为此提出一种基于物理的浑浊水体的真实感光照模拟方法.首先基于物质对水体光学特性的影响对浑浊水体进行建模,并分别建立每一类物质的吸收和散射模型;然后根据光线在浑浊水体中的传播及其与不同物质颗粒的交互作用计算光能的衰减变化,并将其转换为RGB颜色系统进行真实感绘制.借助GPU强大的并行处理能力,该方法可以实现对不同浑浊水体的光照效果的实时绘制.     

卫星表面光学反射特性建模与仿真研究

在研究空间相机成像效果探测问题时,针对提高探测相机成像真实效果的需要,研究了卫星表面光学反射特性的建模与仿真方法.利用双向反射分布函数(BRDF)仿真卫星表面的光学反射特性,将卫星表面物理特性与其光学反射特性有机地结合起来.在VC.Net环境下开发卫星表面光学反射特性仿真软件,并将软件集成到空间探测相机成像效果仿真平台上.利用平台进行成像仿真实验,生成真实感仿真图片.仿真结果表明,BRDF能够精确仿真卫星表面的光学反射特性,使成像效果仿真更加准确和逼真.     

自由多视角恢复表面纹理的三维重建

针对从轮廓恢复形状获得的几何模型,为使其具有真实感,提出了一种基于自由多视角的图像序列为几何模型添加表面纹理的新方法,解决了以往二维图像和三维几何模型配准方法中需人工干预、低精度,速度慢的问题。本文通过设计一个配准模板,实现了全自动、高精度的配准,并利用透视投影变换一次性获得纹理坐标,实现了快速的纹理恢复。实验结果表明,采用这种方法的纹理绘制效果理想,生成的模型真实感强。     

Stereo-based bokeh effects for photography

Bokeh, a sought-after photo rendering style of out-of-focus blur, typically aims at an esthetic quality which is not available to low-end consumer-grade cameras due to the lens design. We present a bokeh simulation method using stereo-vision techniques. We refine a depth map obtained by stereo matching, also using some minor user interaction. Overexposed regions are recovered according to depth information. A depth-aware bokeh effect is then applied with user-adjustable apertures sizes or shapes. We also simulate swirly bokeh, also known as cat-eye effect. Our method mainly aims at the visual quality of the bokeh effect rather than (so far) at time efficiency. Experiments show that our results are natural looking and that they can be comparable to bokeh effects achieved with expensive real-world bokeh-capable camera systems.     

Rendering realistic spectral bokeh due to lens stops and aberrations

Creating bokeh effect in synthesized images can improve photorealism and emphasize interesting subjects. Therefore, we present a novel method for rendering realistic bokeh effects, especially chromatic effects, which are absent for existing methods. This new method refers to two key techniques: an accurate dispersive lens model and an efficient spectral rendering scheme. This lens model is implemented based on optical data of real lenses and considers wavelength dependency of physical lenses by introducing a sequential dispersive ray tracing algorithm inside this model. This spectral rendering scheme is proposed to support rendering of lens dispersion and integration between this new model and bidirectional ray tracing. The rendering experiments demonstrate that our method is able to simulate realistic spectral bokeh effects caused by lens stops and aberrations, especially chromatic aberration, and feature high rendering efficiency.     

Efficiently Simulating the Bokeh of Polygonal Apertures in a Post‐Process Depth of Field Shader

The effect of aperture shape on an image, known in photography as ‘bokeh’, is an important characteristic of depth of field in real‐world cameras. However, most real‐time depth of field techniques produce Gaussian bokeh rather than the circular or polygonal bokeh that is almost universal in real‐world cameras. ‘Scattering’ (i.e. point‐splatting) techniques provide a flexible way to model any aperture shape, but tend to have prohibitively slow performance, and require geometry‐shaders or significant engine changes to implement. This paper shows that simple post‐process ‘gathering’ depth of field shaders can be easily extended to simulate certain bokeh effects. Specifically we show that it is possible to efficiently model the bokeh effects of square, hexagonal and octagonal apertures using a novel separable filtering approach. Performance data from a video game engine test demonstrates that our shaders attain much better frame rates than a naive non‐separable approach.     

General Spectral Camera Lens Simulation

We present a camera lens simulation model capable of producing advanced photographic phenomena in a general spectral Monte Carlo image rendering system. Our approach incorporates insights from geometrical diffraction theory, from optical engineering and from glass science. We show how to efficiently simulate all five monochromatic aberrations, spherical and coma aberration, astigmatism, field curvature and distortion. We also consider chromatic aberration, lateral colour and aperture diffraction. The inclusion of Fresnel reflection generates correct lens flares and we present an optimized sampling method for path generation.     

Efficient Ray Tracing Through Aspheric Lenses and Imperfect Bokeh Synthesis

We present an efficient ray‐tracing technique to render bokeh effects produced by parametric aspheric lenses. Contrary to conventional spherical lenses, aspheric lenses do generally not permit a simple closed‐form solution of ray‐surface intersections. We propose a numerical root‐finding approach, which uses tight proxy surfaces to ensure a good initialization and convergence behavior. Additionally, we simulate mechanical imperfections resulting from the lens fabrication via a texture‐based approach. Fractional Fourier transform and spectral dispersion add additional realism to the synthesized bokeh effect. Our approach is well‐suited for execution on graphics processing units (GPUs) and we demonstrate complex defocus‐blur and lens‐flare effects.     

组合式建筑立面全景图像的渐晕校正

由于组合式建筑立面图像进行全景拼接时,交界处光照度降低,产生渐晕现象,提出一种基于曲面拟合的渐晕校正方法,对组合式建筑立面全景图像渐晕校正。通过推算角点,分析图像坐标系及世界坐标系之间的对照关联,获取世界坐标系中角点的单位坐标数据,构建相机成像的组合式建筑三维交互模型;采用ORB特征匹配算法实施图像匹配,通过分解单应性矩阵,推算相机内部参数的投影转换矩阵、旋转矩阵和平移矩阵,运用柱面坐标投影方法完成建筑立面图像全景拼接;使用基于二维曲面拟合图像灰度校正方法,计算Hesse矩阵的相关系数,利用Hesse矩阵逐次迭代收敛,获得二维曲面参数值,消除图像渐晕现象。仿真结果证明,所提方法能够有效校正组合式建筑立面全景图像渐晕,且校正后的图像灰度分布均匀,缩短了图像渐晕校正时间。     

Design of near-field recording optics using truncated hemispherical SIL with cover-layer incident dual recording layers

In this paper, we propose a novel optics design for media inside near-field recording (NFR) using a truncated hemispherical solid immersion lens (HMS). To obtain strong advantage of data protection and high data capacity simultaneously, a truncated HMS based near field optics with cover-layer incident dual recording layers is designed. In this design, to improve the small optical tolerance of the truncated HMS unit and to adjust dual focusing positions, an additional aspheric lens surface is added on top of the truncated HMS and it is combined with zoom optics composed of two single lenses having a low numerical aperture (NA). Also, to compensate for chromatic aberration, which is a serious problem for optics using a blue laser diode, a diffractive optical element is also designed. Using zoom optics, an additional aspheric lens surface, and a diffractive optical element together, the wavefront aberration and chromatic aberration are effectively reduced in a broad range of cover-layer thicknesses and wavelength variations. In addition, in this paper, the effect of a gap induced aberration is investigated by analyzing the different behavior of each TM and TE wave for the cover-layer incident NFR optics.Paper presented at the 15th Annual Symposium on Information Storage and Processing Systems, Santa Clara, CA, USA, 28–29 June, 2005.     

一种基于斜率的摄像机畸变校正方法

普通 CCD摄像机在成像时都存在畸变成像误差 ,在机器人视觉检测及自动装配中 ,有效地进行误差校正对准确确定物体的位置具有重要的意义 .本文采用带有一阶径向畸变的小孔摄像机模型 ,提出一种基于线段斜率的方法 ,对摄像机镜头的径向畸变进行校正 ,不必标定太多的摄像机的外参数 ,方法简洁 ,适合于视觉系统中对摄像机畸变的实时校正 ,或对摄像机捕获的图像进行几何校正 .实验表明 ,具有很强的鲁棒性和较高的校正精度     

Simple and efficient method of calibrating a motorized zoom lens

In this work, three servo motors are used to independently control the aperture, zoom, and focus of our zoom lens. Our goal is to calibrate, efficiently, the camera parameters for all the possible configurations of lens settings. We use a calibration object suitable for zoom lens calibration to deal with the defocusing problem. Instead of calibrating the zoom lens with respect to the three lens settings simultaneously, we perform the monofocal camera calibration, adaptively, over the ranges of the zoom and focus settings while fixing the aperture setting at a preset value. Bilinear interpolation is used to provide the values of the camera parameters for those lens settings where no observations are taken. The adaptive strategy requires the monofocal camera calibration only for the lens settings where the interpolated camera parameters are not accurate enough, and is hence referred to as the calibration-on-demand method. Our experiments show that the proposed calibration-on-demand method can provide accurate camera parameters for all the lens settings of a motorized zoom lens, even though the camera calibration is performed only for a few sampled lens settings.