飞行仿真中大规模场景渲染技术的研究与实现
摘要
在飞行仿真系统中,三维场景的建模与绘制是使用户产生身临其境和沉浸感的关键技术之一。因此,大规模场景的绘制是飞行仿真系统的一个重要组成部分,它为飞行员提供实际飞行任务中的虚拟环境,其内容的丰富程度、场景的逼真效果和清晰度直接影响着飞行仿真系统的仿真度和飞行训练效果。
本文从实时性要求较高的仿真应用出发,结合项目《X1/X2型飞机台式飞行训练模拟器》和项目《虚拟飞行系统》,在对飞行仿真系统中大规模场景渲染技术进行一定研究的基础上,根据项目的具体需求,设计并实现了两个虚拟场景系统,完成了飞行仿真场景中各景物的绘制。
系统以VC、OpenGL和图形引擎库PLIB为开发工具,使用场景优化和实时绘制技术,模拟的场景逼真、画面流畅。
As an important branch of the modern simulation technology, flight simulation is the outcome of the integration of the fields of system simulation, computer science and the aeronautics. In the flight environment, using the computer simulation technology, taking simulation model instead of the real physical model, helps improving the quality of the testing and research. At the same time, it can repeat the experiment for several times on the computer platforms, analysis and test results to shorten the test and development cycle, reducing costs. In addition, as it is more applicable to the field of combat in the military training and weapons development, provides a very effective and economical way for flight training, tactical exercises and the development of weapons and equipment, it becoming an important high-tech means in the field of military. At present, taking the flight simulation for the flight training is gradually becoming an important way to training the pilot in the military academies.
This paper topics from the development of cooperation project "The Desktop Flight Training Simulator for Training Plane X1 / X2", and the project "Virtual Flight System" , the former is for the real-time simulation flight training, and latter is mainly for the teaching and entertainment, for popularizing to college students the flight knowledge, students can also get relaxed from fatigue. The system, using computer simulation technology, computer-controlled technology, virtual reality technology, offers users a training platform with nearly actual operational interfaces. Structurally speaking, it consists of the controlling hardware equipment and software system of two parts. When users operate the hardware equipment joystick, rudder, throttle, the software system controller accesses and processes the data to produce real time flight simulation of the changes of the plane’s flight pose and the instrument panel, by this way, it relatively realistically simulate a large scale scenes. System provides a number of flight training subjects, Multi-View mode of observation, as well as video playback and flight trajectory simulation, and other functions, and simulates daytime, evening and night scenes and active objectives.
In the flight simulation system, the 3D scene is one of the most important key technologies that enables users have realistic sense of immersion. Therefore, large-scale scene of Flight Simulation System mapping is an important part to provide the pilots the landscape environment for actual mission. The richness, fidelity and clarity of the contents directly affect the training result of the Flight Simulation System Simulation. At present, large-scale scenes rendering is an important field of research of virtual reality and computer graphics field, despite the graphics hardware rendering speed has developed rapidly compared to the past, but still not efficient for the tens of thousands of scenes targets real-time rendering on the big scenes.
This paper, based on the study on the flight simulation system rendering technology for large-scale scenes, According to the different needs, we designed and the realized two Virtual Scene systems, completed the drawing of the scenes of flight simulation. In the design of the two systems, we have adopted the "tree model" for the data structure to manage all objects in the scene. Tree structure in the scene data updates and rapid rendering has strong advantages, at the same time, it has a good integration for the response and detection of the collision in the 3-D scene. Therefore, the whole scene design of systems is consistence; it also provides a facilitated mean for the management scene, thereby it enable the system be expansible for the later extension.
The first chapter makes a brief introduction of the subject sources, the background and significance of flight simulation systems, as well as the development of the status at home and abroad.
Chapter 2 outlines the entire flight simulation system, the system design principles, composition, functions, and so has done, and gives the framework of the system and diagrams. It described the rendering process of the scene subsystem, and a briefly described the main functions of each module. It briefs the OpenGL 3D animation programming packages, as well as the 3-D graphics engine Plib and the graphics API SSG on the basis of the OpenGL.
The third chapter described in detail some of the key technologies of the large-scale scenes rendering. First we introduced the system optimization modeling techniques, including instantiation technology, external references, Hidden Surface Removal technology, texture mapping technology, billboards technology, and divided the terrain generation and real-time display technology development process into four phases : simple terrain generation technology, discrete LOD model, continuous LOD model, multi-resolution model; and introduced each one; the third quarter introduces the irregular object modeling methods such as the process modeling, based on the fractal, cellular automata, particle system and the physical process; Finally, the collision detection technology and the bounding box technology are discussed.
Chapter IV presents the large-scale terrain generation, first it overviews of terrain simulation, and then with the third chapter on the technical and project needs, describes the two implement of terrain simulation: one is to block the terrain first, then based on the re-scheduling AOI terrain scenes scheduling to implement a "real" two-dimensional terrain; another is 3D terrain generation based on discrete LOD simulation model relevant with viewpoint, and with the AABB bounding box implement the detection of the aircraft collision with the ground.
Chapter V, in accordance with optimization and real-time display technology in Chapter III, gives realization of the various elements in the scene, including the loading of aircraft model and the drawing of the cabin and instrumentation, spherical sky, the moon and stars simulation, the changes of the daytime dusk the night of the features, the level stratus, cumulus based on the Billboard technology, buildings, trees, the drawing of the shadow using planar hard shadow rendering algorithm and flame drawing based on particle system.
The system interface is friendly, easy to use, mapping out the scene with a better simulation results. In addition, the system reflects the good performance of real-time, and the system has high reusability and extensibility. Therefore, the functions of the system can be optimized and improved, it also can be taken as the sub system of the other flight simulation system, it has a good commercial value and market prospects. Currently Desktop Flight Simulator Training System has been started to promote the use of several corporations of native air force army, the training effect was very good, virtual flight system also has entered the second phase development.
本文从实时性要求较高的仿真应用出发,结合项目《X1/X2型飞机台式飞行训练模拟器》和项目《虚拟飞行系统》,在对飞行仿真系统中大规模场景渲染技术进行一定研究的基础上,根据项目的具体需求,设计并实现了两个虚拟场景系统,完成了飞行仿真场景中各景物的绘制。
系统以VC、OpenGL和图形引擎库PLIB为开发工具,使用场景优化和实时绘制技术,模拟的场景逼真、画面流畅。
As an important branch of the modern simulation technology, flight simulation is the outcome of the integration of the fields of system simulation, computer science and the aeronautics. In the flight environment, using the computer simulation technology, taking simulation model instead of the real physical model, helps improving the quality of the testing and research. At the same time, it can repeat the experiment for several times on the computer platforms, analysis and test results to shorten the test and development cycle, reducing costs. In addition, as it is more applicable to the field of combat in the military training and weapons development, provides a very effective and economical way for flight training, tactical exercises and the development of weapons and equipment, it becoming an important high-tech means in the field of military. At present, taking the flight simulation for the flight training is gradually becoming an important way to training the pilot in the military academies.
This paper topics from the development of cooperation project "The Desktop Flight Training Simulator for Training Plane X1 / X2", and the project "Virtual Flight System" , the former is for the real-time simulation flight training, and latter is mainly for the teaching and entertainment, for popularizing to college students the flight knowledge, students can also get relaxed from fatigue. The system, using computer simulation technology, computer-controlled technology, virtual reality technology, offers users a training platform with nearly actual operational interfaces. Structurally speaking, it consists of the controlling hardware equipment and software system of two parts. When users operate the hardware equipment joystick, rudder, throttle, the software system controller accesses and processes the data to produce real time flight simulation of the changes of the plane’s flight pose and the instrument panel, by this way, it relatively realistically simulate a large scale scenes. System provides a number of flight training subjects, Multi-View mode of observation, as well as video playback and flight trajectory simulation, and other functions, and simulates daytime, evening and night scenes and active objectives.
In the flight simulation system, the 3D scene is one of the most important key technologies that enables users have realistic sense of immersion. Therefore, large-scale scene of Flight Simulation System mapping is an important part to provide the pilots the landscape environment for actual mission. The richness, fidelity and clarity of the contents directly affect the training result of the Flight Simulation System Simulation. At present, large-scale scenes rendering is an important field of research of virtual reality and computer graphics field, despite the graphics hardware rendering speed has developed rapidly compared to the past, but still not efficient for the tens of thousands of scenes targets real-time rendering on the big scenes.
This paper, based on the study on the flight simulation system rendering technology for large-scale scenes, According to the different needs, we designed and the realized two Virtual Scene systems, completed the drawing of the scenes of flight simulation. In the design of the two systems, we have adopted the "tree model" for the data structure to manage all objects in the scene. Tree structure in the scene data updates and rapid rendering has strong advantages, at the same time, it has a good integration for the response and detection of the collision in the 3-D scene. Therefore, the whole scene design of systems is consistence; it also provides a facilitated mean for the management scene, thereby it enable the system be expansible for the later extension.
The first chapter makes a brief introduction of the subject sources, the background and significance of flight simulation systems, as well as the development of the status at home and abroad.
Chapter 2 outlines the entire flight simulation system, the system design principles, composition, functions, and so has done, and gives the framework of the system and diagrams. It described the rendering process of the scene subsystem, and a briefly described the main functions of each module. It briefs the OpenGL 3D animation programming packages, as well as the 3-D graphics engine Plib and the graphics API SSG on the basis of the OpenGL.
The third chapter described in detail some of the key technologies of the large-scale scenes rendering. First we introduced the system optimization modeling techniques, including instantiation technology, external references, Hidden Surface Removal technology, texture mapping technology, billboards technology, and divided the terrain generation and real-time display technology development process into four phases : simple terrain generation technology, discrete LOD model, continuous LOD model, multi-resolution model; and introduced each one; the third quarter introduces the irregular object modeling methods such as the process modeling, based on the fractal, cellular automata, particle system and the physical process; Finally, the collision detection technology and the bounding box technology are discussed.
Chapter IV presents the large-scale terrain generation, first it overviews of terrain simulation, and then with the third chapter on the technical and project needs, describes the two implement of terrain simulation: one is to block the terrain first, then based on the re-scheduling AOI terrain scenes scheduling to implement a "real" two-dimensional terrain; another is 3D terrain generation based on discrete LOD simulation model relevant with viewpoint, and with the AABB bounding box implement the detection of the aircraft collision with the ground.
Chapter V, in accordance with optimization and real-time display technology in Chapter III, gives realization of the various elements in the scene, including the loading of aircraft model and the drawing of the cabin and instrumentation, spherical sky, the moon and stars simulation, the changes of the daytime dusk the night of the features, the level stratus, cumulus based on the Billboard technology, buildings, trees, the drawing of the shadow using planar hard shadow rendering algorithm and flame drawing based on particle system.
The system interface is friendly, easy to use, mapping out the scene with a better simulation results. In addition, the system reflects the good performance of real-time, and the system has high reusability and extensibility. Therefore, the functions of the system can be optimized and improved, it also can be taken as the sub system of the other flight simulation system, it has a good commercial value and market prospects. Currently Desktop Flight Simulator Training System has been started to promote the use of several corporations of native air force army, the training effect was very good, virtual flight system also has entered the second phase development.
引文
[1] 汪成为等,灵境(虚拟现实)技术的理论、实现及应用,清华大学出版社、广西科学技术出版社,1997 年,第 7 版,17-34。
[2] 李京伟、张利萍,基于虚拟现实技术的飞行视景仿真,计算机工程与设计,2005,26(7),1935-1938。
[3] 童中翔,王晓东,飞行仿真技术的发展与展望,飞行力学,2002年 9 月,20(3),5-8。
[4] 王行仁,飞行实时仿真系统及技术,北京航空航天大学出版社,1998年 9 月,第 1 期,1-62。
[5] 刘兴堂等,论军用模拟训练器/系统的发展趋势,空军工程大学学报,2001 年 8 月,2(4),19-21。
[6] 谢广辉,邱淑范,基于虚拟现实技术的飞行训练模拟器探讨,中国航天,2001,10,26-28。
[7] 姜世发,飞行模拟器的回顾及其发展,电光与控制,1998,26(7),8-12。
[8] 白燕斌,史惠康,OpenGL 三维图形库编程指南,机械工业出版社,1998 年 4 月,256-291。
[9] 和平鸽工作室,OpenGL 高级编程与可视化系统开发(系统开发篇),中国水利水电出版社,2006 年 1 月,第 2 版,236-431。
[10] 和平鸽工作室,OpenGL 高级编程与可视化系统开发(高级编程篇),中国水利水电出版社,2006 年 1 月,第 2 版,68-362。
[11] A Flight Simulation Software,http://plib.sourceforge.net。
[12] David E S,et al,Texturing and Modeling: A Procedural Approach,Academic Press,1998,2,5-27。
[13] Mason Woo,et al,OpenGL Architecture Review Board,OpenGL 1.2 Programming Guide,3rd edition,Addison-Wesley,1999,309-312。
[14] 齐敏,郝重阳,佟明安,三维地形生成及实时显示技术研究进展,中国图像图形学报,2000,5(4),269-275。
[15] 王永明,地形可视化,中国图像图形学报,2000,5(6),449-456。
[16] 张芹,谢隽毅等,火焰、云、烟等不规则物体的建模方法综述,中国图像图形学报,2003 年 3 月,5(3) ,186-190。
[17] Ebert DS,Advanced Modeling Techniques for Computer Graphics,ACM Computing Surveys,1996,28(1) ,153-156。
[18] Perlin K , An Image Synthesizer , ACM SIGGRAPH Computer Graphics ,1985,19(3) ,287-296。
[19] Nishita T,Takao S,Katsumi T,et al ,Display of the earth taking into account atmospheric scattering,Proceedings of SIGGRAPH 1993, Anaheim,California,1993,175-182。
[20] Dobashi Y,Nishita T,Yamashita H,et al,Modeling of Cloud from Satellite Images Using Metaballs,Proceedings of the 4th Pacific Conference,1998,53-60。
[21] Agui T, Kohno Y, Nakajima M,Generating 2-dimensional flame images in computer graphics. IE CE Transactions,1991,E74 (2) ,457-458。
[22] Chiba N,Muraoka K,Takahashi H,et al,Two-dimensional visual simulation of flames,smoke and the spread of fire.,The Journal of Visualization and Computer Animation.,1994,,37-53。
[23] Stam Jos,Fiume Eugene,Depicting fire and other gaseous phenomena using diffusion processes,ACM Computer Graphics,1994,29 (4),129- 135。
[24] Nishita,Tomoyuki,Miyawaki,et al. A shading model for atmospheric scattering considering luminous intensity distribution of light sources,ACM Computer Graphics ,1987,21 (4) ,303-310。
[25] Willis P J,Visual simulation of atmospheric haze,Computer Graphics Forum,1987,6,35-42。
[26] Blinn J F,Light reflection functions for simulation of clouds and dusty surfaces,ACM Computer Graphics ,1982,16(3),21-29。
[27] Kajiya,James,Kay Timothy,Rendering fur with three dimensional textures,ACM Computer Graphics,1989,23 (3) ,271-280。
[28] Rushmeier, Holly,Torrance Ken,The zonal method for calculating light intensities in the presence of a participating medium.ACM Computer Graphics,1987,21 (4) ,293-302。
[29] Sakas G,Fast rendering of arbitrary distributed volume densities,Elsevier Science Publishers B. V,1990,519- 530。
[30] Stam Jos , Fiume Eugene , Turbulent wind fields for gaseous phenomena,ACM Computer Graphics,1993,27 (4),369-375。
[31] Fournier A F,Fussell D,Carpenter L,Computer rendering of stochastic models,Communications of the ACM ,1982,25(6),371-384。
[32] Max N,Crawfis R,Williams D,Visualizing wind velocities by advocating cloud textures,IEEE CS Press,1992,179-183。
[33] Sakas G,Modeling and animating turbulent visual computer,1993,9,200-212。
[34] C F Li,Y T Feng,D R J Owen,SMB:Collision detection based on temporal coherence,Computer methods in applied methods in applied mechanic and engineering,2006,195,2252-2269。
[35] 魏迎梅,王涌,石教英,碰撞检测中的层次包围盒方法,计算机应用,2000,20,241-243。
[36] 李井辉,申静波,基于包围盒的碰撞检测技术研究,高校实验室工作研究,2006 年 12 月,90(4),31-34。
[37] 马东华,大规模场景管理与漫游技术的研究与实现,北京邮电大学硕士论文,37-44。
[38] Geoffre S. Hubona,Philip N. Wheeler,GregoryW. Shirah and Matthew Brandt,The role of object shadows in promoting 3D visualization,ACM Transactions on Computer-Human Interaction,1999,6(3),214-242。
[39] Pascal Mamassian,David C. Knill,and Daniel Kersten,The perception of cast shadows.,Trends in Cognitive Sciences,1998,2(8),288-295。
[40] Leonard Wanger,The effect of shadow quality on the perception of spatial relationships in computer generated imagery , Computer Graphics,,1992,25(2),39-42。
[41] Blinn J F,Jim blinn’s corner: Me and my (fake) shadow,IEEE Computer Graphics & Applications,1988,8(1),82-86
[42] 张芹,吴慧中,谢隽毅,张正军,基于粒子系统的火焰模型及其生成方法研究,计算机辅助设计与图形学学报,2001,13(1),78-82。
[2] 李京伟、张利萍,基于虚拟现实技术的飞行视景仿真,计算机工程与设计,2005,26(7),1935-1938。
[3] 童中翔,王晓东,飞行仿真技术的发展与展望,飞行力学,2002年 9 月,20(3),5-8。
[4] 王行仁,飞行实时仿真系统及技术,北京航空航天大学出版社,1998年 9 月,第 1 期,1-62。
[5] 刘兴堂等,论军用模拟训练器/系统的发展趋势,空军工程大学学报,2001 年 8 月,2(4),19-21。
[6] 谢广辉,邱淑范,基于虚拟现实技术的飞行训练模拟器探讨,中国航天,2001,10,26-28。
[7] 姜世发,飞行模拟器的回顾及其发展,电光与控制,1998,26(7),8-12。
[8] 白燕斌,史惠康,OpenGL 三维图形库编程指南,机械工业出版社,1998 年 4 月,256-291。
[9] 和平鸽工作室,OpenGL 高级编程与可视化系统开发(系统开发篇),中国水利水电出版社,2006 年 1 月,第 2 版,236-431。
[10] 和平鸽工作室,OpenGL 高级编程与可视化系统开发(高级编程篇),中国水利水电出版社,2006 年 1 月,第 2 版,68-362。
[11] A Flight Simulation Software,http://plib.sourceforge.net。
[12] David E S,et al,Texturing and Modeling: A Procedural Approach,Academic Press,1998,2,5-27。
[13] Mason Woo,et al,OpenGL Architecture Review Board,OpenGL 1.2 Programming Guide,3rd edition,Addison-Wesley,1999,309-312。
[14] 齐敏,郝重阳,佟明安,三维地形生成及实时显示技术研究进展,中国图像图形学报,2000,5(4),269-275。
[15] 王永明,地形可视化,中国图像图形学报,2000,5(6),449-456。
[16] 张芹,谢隽毅等,火焰、云、烟等不规则物体的建模方法综述,中国图像图形学报,2003 年 3 月,5(3) ,186-190。
[17] Ebert DS,Advanced Modeling Techniques for Computer Graphics,ACM Computing Surveys,1996,28(1) ,153-156。
[18] Perlin K , An Image Synthesizer , ACM SIGGRAPH Computer Graphics ,1985,19(3) ,287-296。
[19] Nishita T,Takao S,Katsumi T,et al ,Display of the earth taking into account atmospheric scattering,Proceedings of SIGGRAPH 1993, Anaheim,California,1993,175-182。
[20] Dobashi Y,Nishita T,Yamashita H,et al,Modeling of Cloud from Satellite Images Using Metaballs,Proceedings of the 4th Pacific Conference,1998,53-60。
[21] Agui T, Kohno Y, Nakajima M,Generating 2-dimensional flame images in computer graphics. IE CE Transactions,1991,E74 (2) ,457-458。
[22] Chiba N,Muraoka K,Takahashi H,et al,Two-dimensional visual simulation of flames,smoke and the spread of fire.,The Journal of Visualization and Computer Animation.,1994,,37-53。
[23] Stam Jos,Fiume Eugene,Depicting fire and other gaseous phenomena using diffusion processes,ACM Computer Graphics,1994,29 (4),129- 135。
[24] Nishita,Tomoyuki,Miyawaki,et al. A shading model for atmospheric scattering considering luminous intensity distribution of light sources,ACM Computer Graphics ,1987,21 (4) ,303-310。
[25] Willis P J,Visual simulation of atmospheric haze,Computer Graphics Forum,1987,6,35-42。
[26] Blinn J F,Light reflection functions for simulation of clouds and dusty surfaces,ACM Computer Graphics ,1982,16(3),21-29。
[27] Kajiya,James,Kay Timothy,Rendering fur with three dimensional textures,ACM Computer Graphics,1989,23 (3) ,271-280。
[28] Rushmeier, Holly,Torrance Ken,The zonal method for calculating light intensities in the presence of a participating medium.ACM Computer Graphics,1987,21 (4) ,293-302。
[29] Sakas G,Fast rendering of arbitrary distributed volume densities,Elsevier Science Publishers B. V,1990,519- 530。
[30] Stam Jos , Fiume Eugene , Turbulent wind fields for gaseous phenomena,ACM Computer Graphics,1993,27 (4),369-375。
[31] Fournier A F,Fussell D,Carpenter L,Computer rendering of stochastic models,Communications of the ACM ,1982,25(6),371-384。
[32] Max N,Crawfis R,Williams D,Visualizing wind velocities by advocating cloud textures,IEEE CS Press,1992,179-183。
[33] Sakas G,Modeling and animating turbulent visual computer,1993,9,200-212。
[34] C F Li,Y T Feng,D R J Owen,SMB:Collision detection based on temporal coherence,Computer methods in applied methods in applied mechanic and engineering,2006,195,2252-2269。
[35] 魏迎梅,王涌,石教英,碰撞检测中的层次包围盒方法,计算机应用,2000,20,241-243。
[36] 李井辉,申静波,基于包围盒的碰撞检测技术研究,高校实验室工作研究,2006 年 12 月,90(4),31-34。
[37] 马东华,大规模场景管理与漫游技术的研究与实现,北京邮电大学硕士论文,37-44。
[38] Geoffre S. Hubona,Philip N. Wheeler,GregoryW. Shirah and Matthew Brandt,The role of object shadows in promoting 3D visualization,ACM Transactions on Computer-Human Interaction,1999,6(3),214-242。
[39] Pascal Mamassian,David C. Knill,and Daniel Kersten,The perception of cast shadows.,Trends in Cognitive Sciences,1998,2(8),288-295。
[40] Leonard Wanger,The effect of shadow quality on the perception of spatial relationships in computer generated imagery , Computer Graphics,,1992,25(2),39-42。
[41] Blinn J F,Jim blinn’s corner: Me and my (fake) shadow,IEEE Computer Graphics & Applications,1988,8(1),82-86
[42] 张芹,吴慧中,谢隽毅,张正军,基于粒子系统的火焰模型及其生成方法研究,计算机辅助设计与图形学学报,2001,13(1),78-82。