建筑场景实时漫游和日照仿真

【作者】 肖丹；

【导师】 潘志庚；

【作者基本信息】 浙江大学 ， 计算机应用， 2002， 硕士

【摘要】 虚拟现实（VR）、计算机辅助设计（CAD）和科学计算可视化应用通常要求能够对复杂的场景结构进行交互式显示和观察。随着虚拟现实应用的发展，人们要求实时地生成高质量的画面。用传统的图形学方法，首先要建立场景的三维几何模型，然后对场景物体表面的材料、光照、纹理等进行描述。这样的处理过程非常耗时，往往需要很昂贵的硬件开销，并且还要在场景的复杂程度和图形的真实感两者之间进行折中。因而研究人员提出了基于图象的造型和绘制方法。二种方法各有优缺点。为了减少最终绘制的场景复杂度，作为实时图形生成技术重要的一部分，本文在前一部分主要研究基于几何和纹理混合简化的绘制技术。 另外，虚拟环境的实时绘制是实现虚拟系统的关键之一。室内场景的模拟和一日内室内所有的日照强度对于想选择一个合适的房屋居住的住户来说非常地重要。所以在本文的第二部分我们还研究了与人们日常生活息息相关的建筑物日照问题，通过设定建筑物的经纬度，高度等信息，计算建筑物的日照强度和实时模拟室内日照效果。 本文第一章简单介绍了VR（Virtual Reality）的基本概念、重要特点以及VR系统的分类和应用领域。给出了VR中实现图形实时生成的有关方法，建筑场景实时漫游，以及研究建筑物日照仿真的重要性。最后给出论文的组织方式和本文的要讨论的问题。 本文第二章讨论建筑场景实时漫游的绘制技术，对在漫游场景中存储一部分图象对复杂几何场景进行简化的这一思想的发展和一些方法进行介绍。并由此引出我们的研究工作和本文将提到的算法。 本文第三章研究了一种相对较新的基于几何和图象混合简化方法的实时漫游算法，该算法能进行几何-纹理相互转换，通过对纹理投影面后的几何插值，生成退化几何，实现几何-纹理间的光滑过渡。该算法的一个显著特点是结合了几何和纹理层次细节的思想。最后讨论了算法的应用。 本文第四章具体分析了第三章中的算法实现过程，通过图例显示了实验结果，说明了该算法所提出方法的有效性。 本文第五章给出了计算建筑物日照的数学模型，借助该模型我们可以实现在任一给定经纬度的室内建筑在任一给定的时刻房间内光照的强度；并结合辐射度算法我们可以模拟建筑物的光照效果。本章的最后将分析一组室内房间一天中随时间和光照强度改变所形成的场景动画。 摘 要 浙江大学硕土学位沦文 最后是本文的结论，以及今后将继续对本算法进行的完善工作。更多还原

【Abstract】 Virtual reality (VR) applications, computer-aided design (CAD) applications and scientific visualizations often need user-steered interactive displays of veiy complex polygonal environments, for which, however, the computation and storage requirements r exceeds the capacity of modem graphics hardware on PC. Thus Image-based rendering (IBR) representations are presented by researchers recently. In the first part, this thesis focuses on the real-time rendering of scenes based on geometric and image simplificaliom In addition, teal-time display of virtual scenes is the key issue for a successful virtual reality system. The simulation of indoor scenes and the indoor duration of sunlight in one day have an essential meaning to real estate clients who want to choose an appropriate room to live in. So in the second part of our article, we introduce computation of imdiazing Iixzrs and sunlight simulation of indoor scenes. In Chapter 1, we first describe the basic concepts and primary characteristics of VR systems. Then we briefly discuss the application of VR in architectural simulation, real-time wa]ktbrough of architectural scenes, and sunlight simulation. In Chapter 2, we introduce some related research works, research contents about real-time walkllmugh of architectural scenes. In Chapter 3, we present a relatively new simplification approach which dynamically represent geometric complexity using textures. This approach discuss how to create a system that renders the nearby subset of a model as geometry and the distant, but visible subset of a model with a texture-based representation. The principal contribution of this algorithm performs smooth transition between geometry and texture by morpbing the near geometry. One novel idea is that it takes advantage of the LaD of geometry and texture. In Chapter 4, the author presents the concrete implementation of the algorithm, which includes the data structures and the description of some procedures. We give present some test results comparing our algorithm with others. In Chapter 5, the author simulates sunlight effects of indoor scenes with astronomical calculation and computer graphics rendering. The rendered phenomena look like real sunlight streaming into an interior through an outside window At first, users interactively input date, location of the observed room, and turbidity of atmosphere. With these parameters, we can then calculate the sun’s angle of altitude, azimuth, and luminous intensity in terms of formula derived from astronomy and geography. By wmparing the sun’s angle of altitude to nearby building’s angle of altitude at the same sun’s azimuth, we can find out whether the observed room can receive the sunlight’s irradiation. Accumulating the period of time in which the sun’s angle of altitude is larger than that of nearby building’s, we obtain the sunlight irradiating hours of observed room. Given the luminous intensity in a room at a specific time, we can also determine the room’s energy and the spots receiving sun’s direct irradiation. We take sunlight shining from window as parallel lines and find out meshes that have intersections with those lines, and then distribute the sun’s energy to those meshes. Thus we can simulate the indoor scenes with radiosity algorithim Finally, we draw the general conclusion of our paper in the last paragraph. Future work plan on this specific topic is also included.更多还原