Virtual Natural Environment Technique Research Based On GPU Programme

GPU's rapid development beyond the speed of the semiconductor technology Moore's Law three times provides an unprecedented new tool and technology for the development to achieve large-scale real-time 3D simulation system, which will greatly promote cognitive enhancement of people's awareness of the 3D simulation system. Virtual Natural Environment surpasses the expression of entities in VR, it mainly includes the Virtual Geographic Environments(VGE),Virtual Physical Environment(VPE) and Virtual Meteorological Environment (VME) and many other abstract but objective themes, which depicts a greater sense of immersion and more comprehensive expression of the space environment.Based on integration of current domestic and foreign advanced technology, combining advanced GPU programming, in this paper we strive to build a complete technology system of Virtual Natural Environment implementation. The content of this paper focus on model building and GPU's implement of VGE, VPE and VME's field. The chapters are organized independently and the topic is clear, but all are related with research content and realization of VNE.In chapter 1, we discuss the development of spatial cognition and regard technology development and means updating as the important factors influencing spatial information expression. Based on this and combining the great updating in current performance of advanced GPU graphics developing, we launch the cognition system structure of"Virtual World". Then we point out that virtual world can be divided in"VNE"(Virtual Natural Environment) and"Virtual Society", and the division standard depends on"whether there are people participating or not". Then we analysis the constituent system of VNE, confirm the three fields of VGE, VPE and VME as the content of VNE and discuss the content and technology realization of each theme. With regards to Virtual Reality and Virtual World, we discuss the relation between virtual reality technology and virtual world (including its researching branches) and make it clear that"Virtual World"is the goal while virtual reality technology is only a researching means ,a realization way. Finally we point out that virtual world's perfect state is the full and vivid image of real world, the purpose of building virtual world are to create a restorable world for us to destroy more than to deduce and review the time frame of things. So that it can provide human activities, scientific experiment and environmental assessment with a lively experiment platform.As the major background, the functional structure of the GPU and GPU programming aspects are discussed in detail in this paper. With regard to GPU's hardware performances upgrade and function expansion, we outline GPU's functional properties and evaluation standard of the performances in different period and establish GPU programmability as the new evaluation standard of GPU performances. It highlights that GPU will be the inevitable developing trend in the new generation of graphic system development. We also combine 3D graphic system development and introduce both old and new 3-D graphics system rendering. Then we point out several great advantages of GPU graphic development in strong function support, fast rendering and flexibility. GPU programming is of the mechanism that differs from the traditional algorithm idea and it mainly gears to the pixel and vertex data to program .Its realization relies on rapid parallel computing technology of large array. We also brief GPU programmable language grammar with programming ideas as the main realization basis.In the research on virtual geographic environment, our main content focus on regional terrain visualization, illumination rendering and water visualization.On regional terrain visualization technology, there are three themes to address: model expression, texture creation and rendering mechanism. The main research focuses on how to work out the contradiction between real-time efficiency and visual quality in regional expression. We have two resolution ways: the first one is to optimize the regional visualization strategy in traditional terrain express algorithm. The second is using GPU to build rapid rendering mechanism without model data structure.Concerning the first technology, we discuss the real-time optimization automation model (Roam) whose realization bases on the bi-buffer queue of the binary tree and introduce the advanced PLSM that can comply with the regional block scheduling topography. As PLSM has many advantages, such as its incident wiretapping drive, independent GPU rendering ways, efficient dispatching strategy of simulating operation system, it fits regional terrain dispatch and express. So we combine Roam algorithm and PLSM to implement efficient regional rendering. Roam algorithm, as triangulation modeling algorithm, is directly in charge of LOD modeling while PLSM is in charge of terrain attempering, data interface and independent rendering mechanism etc.Concerning the second technology, this paper discusses the classic terrain express algorithm realized by GPU. That is the common scientific achievements of Stanford University in the United States and Microsoft Research Institute----Nested-grid model algorithm implementation mechanism based on the geometric cut. This algorithm's advantage is that it doesn't need to build complex terrain model and almost all the work can be done efficiently in GPU at the cost of occupying more GPU computing resources, thus it is a clever algorithm. Combining my previous research on terrain express model based on the same level with multi-resolution, I launch some improving ideas of this model and establish the multi-resolution model terrain expression of integrated nested grid in this paper. The main improvement is to establish level distribution of multi-resolution based on horizon and distance and thus to implement the LOD terrain model express of precision control.On texture creation, as there are difficulties in texture acquiring, matching and multi-resolution express of regional terrain express. In this paper, a dynamic texture creation method of Texture Splatting is discussed. The advantage of this method is that we can not only get dynamic texture but also synthesize texture with its constituent. Then we can get matching texture with considerably good simulation without real texture by texture distribution map of its various components. This paper also launches an improved compensation texture synthesis way which is based on Texture Splatting , can increase rendering efficiency and would not affect the rendering flexibility of dynamic texture expression. The idea of this approach is to divide the procedure into two periods. In the former period, static texture component synthesis pre-processing is finished. In the latter one, real-time texture component compensation overlaying of tense texture(like snow, water surface) is completed and part of illumination computing is done in this period. In this way, real-time efficiency of regional express is greatly enhanced.On rendering mechanism, the traditional pipeline has to withdraw from the historical stage at the real-time requirement of large area rendering. In large 3-D visualization system, GPU independent rendering express mechanism is adopted. Using GPU, rendering can be independent from terrain modeling and a set of customization programs can be created for one model. It is very simple to describe the rendering program. With rendering script, the program can be sent to GPU by 3-D engine. Knowledge on this aspect is introduced in detail in the paper.On natural lighting effects of VGE, we mainly analysis the basic principles of light synthesis from simple to complex and in depth from the physical optics aspect and achieve the effect imitation of CD diffraction interference wave using physical optics analysis. This goes deep into the micro physical-particle world to explore the unification of natural discipline and natural phenomena. In this paper, first we introduce the expansion models of illumination model, spotlight effect, optical attenuation effect which comply with the pipeline way, then the technology accomplishment of environment image mapping. The advantage of GPU programming flexibility and strong function expansion can be full embodied through GPU programming technology. And this supplies help for complex light rendering realization. As certification of this point, we complete wave interference simulation by physics beam particle tracking.On water surface expression model, we review three expressions: texture wave, Geometry and physics-wave technology. On texture wave expression, according radical sampling LOD expression of static grid data, we put forward elliptical sampling expression model which is more scientific and is confirmed by view sight and location. This model can also be applied to terrain model of Grid-DEM expression. In texture wave superposition method of water surface express, we put forward texture wave superposition and replacement method through signal pulse-driven and texture superposition algorithm using GPU programming express. In water surface geometric express, we define directions of irregular shape radiation wave in the way of texture wave using distance transform of map algebra and express wave radiation of much wave resources in water with obstacles. At the same time, we discuss the common algorithm of geometric wave sampling based on fast Fourier transform (FFT). In water surface physical express, combining Gerstner wave in fluid dynamics, we realize the transform from mathematical model to physical model and deduce physical wave express model in outside force and finally accomplish the model expression ingeniously in GPU.As another important theme of VNE, virtual physical environment is an abstract technology realization. It primarily provides a mechanism of physical space expression. With this mechanism, entities'actions passively display corresponding physical movement under the space constraint. In this aspect, this paper mainly discusses current physics acceleration hardware technology line and demonstrates physical engine mechanism realization by the example of Newton physical engine. Then we analysis function structure and technology framework of physical engine and exemplifies the experiment of collision with the earth to discuss the physical engine use. Finally, with GPU programming as tools, we use the bouncing ball simulation to reflect the support capacity of GPU for physics computation and physical phenomena simulation.In virtual meteorological environment expression, this paper summarizes several technology ways of creating virtual meteorology expression and introduces the advanced directly Visualization Technology (Splatting) in detail. As for the common particle system expression, we launch particle-oriented GPU unified model with common express which integrates particles drawing, sports updates and light rendering expression. Also this new model can deal with real-time and dynamic generating particles with random sampling static particles and meteorological model. This provides a united realization mode of GPU programming for virtual meteorological phenomena simulation.In the final part of this paper, focusing on comprehension of technology and realization of VNE, we discuss theme integration, effects integration and technical cooperation. The content includes relation layout of VGE,VPE and VME; Graphic Rendering, light effects, effect integration of physical calculation,CPU, GPU and PPU technical collaboration and so on.From the whole view, this paper discusses the model expression of all branches of VNE tightly and simulation technology of GPU programming. As the main purport of this paper, our primary task is to explore the technology line of establishing virtual natural environment, the architecture and integrated support of the model.