【作者】 谢文明；

【导师】 孟新； 彭晓东；

【作者基本信息】 中国科学院研究生院（空间科学与应用研究中心） ， 计算机应用技术， 2010， 硕士

【摘要】 随着航天技术的发展和计算机图形学的进步,人们对空间任务仿真可视化的效果需求越来越高。光线追踪是一种基于几何光学原理生成真实感图形的通用技术,它采用一种统一的模型来模拟光源和环境入射光在物体表面产生的漫反射、镜面反射和散射、介质中产生的透射、折射和衰减等光学现象,实现场景消隐、阴影生成、水面波动、大气效果等复杂特效的渲染。将光线追踪算法引入到空间场景的渲染中,不仅可以较真实的展现可见光波段的空间科学任务,而且可以应用到不具备光谱特性的科学数据的可视化中。本文研究了如何将场景信息进行组织以形成适合于光线追踪算法加速的数据形式,同时解决了如何将3DS格式模型转化为本系统的基本图元。为了生成更为真实的图像,本文引入了Mersenne Twister随机扰动来对漫反射光线进行追踪,同时使用比耳定律来模拟光线在半透明物体中的衰减以及根据Monte Carlo理论来生成软阴影,形成了非常逼真的渲染效果。在大气效果绘制方面,对Nishita单散射模型的建立过程进行了详细介绍,并指出了O’Neil大气散射绘制的不足,将其改造为光线追踪模式融入到本文所建立的渲染系统中。最后,本文采用模块化的方式基于分层组织的思想设计了一个通用、可扩展的光线追踪系统,为以后空间任务的可视化提供了一个基础框架。更多还原

【Abstract】 With the development of space technology and advances in computer graphics, the expected effects of the space mission simulation and visualization have been growing. Ray tracing is a generic technology based on geometrical optics to generate realistic images, which uses a uniform model to simulate optical phenomena such as diffuse reflection, specular reflection and scattering at surface and transmission, refraction and attenuation at medium, to achieve complex special effects rendering such as scene blanking, shadow generation, water fluctuations and atmospheric effects. The ray tracing algorithm is introduced to render the space scene, not only can factually show the space science missions with visible light, but also can be applied to visualize scientific data with no spectral characteristics.This article studies how to organize scene data to form a special data format for accelerating ray tracing algorithm, and discusses how to change 3DS format model into basic element supported by the system.In order to generate more realistic images, this paper introduces the Mersenne Twister random perturbation to track the diffuse light, and use Beer’s law to simulate the light attenuation in the semi-transparent objects and generate soft shadows according to Monte Carlo theory. Finally, it formed very realistic rendering effects.In terms of drawing atmospheric effects, this paper describes the process of Nishita single scattering model in detail, points out the lack of drawing atmospheric scattering by O’Neil, and transforms it into ray tracing mode for this rendering system.Finally, this article designs a generic, distensible ray tracing system with modular approach based on ideas of hierarchical organization and provides a basis framework for future visualization space missions.更多还原