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学科主题: 计算机应用::计算机图形学
题名:
光学成像效果真实感绘制技术研究
作者: 吴佳泽
答辩日期: 2011-05-31
导师: 胡晓惠
专业: 计算机应用技术
授予单位: 中国科学院研究生院
授予地点: 北京
学位: 博士
关键词: 光学镜头模型 ; 光学成像效果 ; 真实感绘制 ; 分布式光线追踪
摘要: 光学成像效果是与光学镜头成像特性相关的一类光学效果,常见的包括景深、渐晕、光学像差、散景、眩光等效果,在计算机生成的图像中加入这些效果可以增强图像的真实感和逼真度。本文的研究工作主要致力于解决在计算机合成图像中加入复杂的真实感的光学成像效果这一问题,以增强图像的真实感和逼真度。具体工作包括:
1)针对现有光学镜头模型精度不高的问题,提出一个更加精确的光学镜头模型。该模型通过建立镜头表面模型和色散模型,以对各种复杂的物理镜头进行精确建模,再结合镜头内的光线追踪模型,即可对物理镜头的各种光学成像特性进行精确模拟。为了增强模型的实用性,结合镜头设计原理和摄影原理,提出多个镜头光学特性模型以控制模型的光学成像性能,并引入一个或多个相应的镜头参数以控制每个镜头特性,因而使用者无需掌握太多与镜头相关的光学知识,即可通过调节该模型的参数完成各种光学成像效果的模拟。
2)针对现有方法绘制的散景效果真实感较差的问题,提出一种基于光阑的散景效果真实感绘制方法。该方法以光线传播的折射定律为基础,利用序列光线追踪方法对光学镜头的光学成像特性进行精确建模;对光学镜头的内部结构进行精确模拟,包括孔径光阑和渐晕光阑,以绘制出由孔径形状和渐晕共同作用的散景效果;利用几何光学理论和序列光线追踪方法精确计算出出射光瞳的位置和大小,以辅助光线采样,提高光线追踪效率。
3)提出一种基于单色像差的散景效果真实感绘制方法,该方法基于真实感的光学镜头模型和分布式光线追踪算法。首先从光学理论上对散景和光学像差的关系进行了分析,包括四种像差,即球差、慧差、像散和场曲。在此基础上,引入一个基于物理的光学镜头模型以精确建模光学像差,该模型以详细的镜头描述作为输入。利用镜头内的光线追踪算法计算出入射光瞳和出射光瞳的的位置和直径,以实现高效的光线采样。为了与双向光线追踪算法进行集成,提出了一种通用的序列光线追踪算法。
4)提出一种基于色差的散景效果真实感绘制方法,该方法采用精确的光谱光学镜头模型和高效的光谱绘制技术。首先从光学理论上分析复杂物理镜头的色差对散景效果的影响;在此基础上,引入一个精确的光谱镜头模型以精确建模镜头色差,同时提出一种镜头内的色散光线追踪算法,以与双向光线追踪算法进行集成;提出一种简单高效的光谱采样技术以支持镜头色散的建模,同时对双向光线追踪算进行改进以集成所提的光谱镜头模型。
5)提出一种新方法以精确模拟不同视觉条件下的人眼视觉图像,该方法采用一个精确的人眼模型,以模拟人眼的解剖学和光学特性;该模型包括Navarro示意眼模型和相应的调节模型组成,这两个模型共同用于模拟人眼可变的折射能力;最后的绘制实验利用分布式光线追踪技术合成出多种真实感的人眼视觉效果。
英文摘要: As optical effects caused by physical lenses, optical imaging effects are various, including depth of field, bokeh, optical aberration, vignetting and glare. Accurate simulating of these effects can improve the realism and fidelity of the rendered images. This dissertation focuses on simulating optical imaging effects in the computer-synthesized images to enhance their realism and fidelity. It includes the following topics:
1) Motivated by inaccuracy of existing camera lens models, an accurate lens model is proposed. This model employs lens surface modeling to accurately model the geometry of complex physical lenses, and combines dispersion modeling and ray tracing techniques inside this model to accurately simulate the optical properties of physical lenses. To improve the practicability of this novel model, multiple optical models are presented, according to lens design and photograph principles, to control its optical lens properties, and corresponding parameters are introduced to control each lens property. As a consequence, users can simulate complex lens-related effects by tuning these lens parameters without too much expertise on lens optics.
2) Based on geometrical optics theory, a new method for realistic rendering of bokeh effect is proposed to improve poor rendering quality of existing methods. A sequential ray tracing method, based on refraction law for transporting light, is employed to accurately model optical imaging characteristics of a camera lens; the internal structure of a camera lens is precisely simulated, including aperture stop and vignetting stop, in order to simulate bokeh effect affected by both aperture shape and vignetting; Based on geometrical optics theory and sequential ray tracing method, position and size of exit pupil in a camera lens are calculated and used for helping ray sampling and advancing efficiency of ray tracing.
3) A novel realistic bokeh rendering method, based on an accurate camera lens model and distributed ray tracing, is presented. An optical analysis of the relationship between bokeh and optical aberrations, including spherical aberration, coma, astigmatism and field curvature, is firstly introduced. Based on this analysis, a physically-based camera lens model, which takes detailed lens prescription as input, is then introduced for accurately modeling the aberrations. The position and diameter of the entrance and exit pupils are calculated by tracing rays inside the lens for achieving efficient ray sampling, and a general sequential ray tracing algorithm is proposed to better combine with bidirectional ray tracing. Furthermore, correct integration between the lens model and bidirectional ray tracing is also analyzed.
4) A novel realistic bokeh rendering method, based on an accurate spectral lens model and an efficient spectral rendering approach, is proposed. A concise optical analysis is firstly introduced on how bokeh appearance is influenced by chromatic aberrations of complex physical lenses. A physically-based spectral lens model, which takes real lens prescription as input, is then introduced for accurately modeling the chromatic aberrations, and a sequential dispersive ray tracing algorithm inside the lens is proposed to better join with bidirectional ray tracing. A new spectral rendering scheme is introduced to accelerate rendering of lens dispersion and support integration between the lens model and bidirectional ray tracing.
5) A novel method is proposed to accurately simulate the human vision under different visual perception. This method introduces an accurate eye model to reasonably predict the anatomical and optical properties of the human eye. This eye model is composed of the Navarro schematic eye model with aspherical surfaces as a basic model, and a corresponding accommodation model, which are combined to simulate the varying refractive power of the human eye. Distributed ray tracing technique is combined with this eye model to produce a variety of visual results.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.iscas.ac.cn/handle/311060/10428
Appears in Collections:综合信息系统技术国家级重点实验室 _学位论文

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Recommended Citation:
吴佳泽. 光学成像效果真实感绘制技术研究[D]. 北京. 中国科学院研究生院. 2011-05-31.
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