Research On Simplification And Real-time Rendering Technology Of 3D Terrain

In many 3D virtual environments,3D terrain is one of the most important elements.Because the terrain has the inherent characteristics of wide coverage area and large amount of data,how to render 3D terrain in real time in application scenes such as GIS,military simulation system and large-scale 3D games has always been an important problem in graphics.In recent years,with the continuous warming of application technologies such as "Digital Earth" and VR,how to simplify and render 3D terrain in real time has become one of the research hotspots in graphics.Based on this background,in order to achieve real-time roaming rendering of global 3D terrain,this paper studies the technologies of large-scale terrain simplification and real-time rendering.There are two major problems in large-scale terrain rendering.One is that the graphics card is a system with limited resources,which can't process massive terrain data in real time.The second is that when the terrain scale is too large,the memory can't load all the data.In order to solve these two problems,this paper makes a deep research on the current mainstream dynamic multi-resolution LOD terrain rendering algorithm based on Quadtree and out of core technology based on the strategy of layering and blocking,makes targeted improvement and optimization,and puts forward a complete technical scheme of simplification and real-time rendering for the global 3D terrain,which realizes the efficient real-time rendering of the global terrain.To sum up,the main research work and contributions of this paper are as follows:1.Analyze the problems existing in the global SRTM terrain elevation data,and use techniques such as void-filling processing,edge connection processing,and cubic spline interpolation scaling to make the terrain data meet the requirements of quadtree LOD algorithm for terrain rendering.2.This paper studies the common layering and blocking strategy in out-of-core technology,and proposes a scheme to divide the global terrain into multiple layers,which avoids the excessive external data redundancy caused by the traditional pyramid model.At the same time,the incremental data scheduling scheme based on viewpoint-related cropping and the double-buffer algorithm based on the LRU strategy are used to achieve efficient internal and external scheduling of global terrain data.3.The common LOD algorithms are compared and analyzed,and the dynamic multiresolution LOD terrain rendering algorithm based on quadtree is studied.Through the establishment of a more simple and effective node evaluation system,and the use of improved multithreading scheme,the real-time simplified rendering of global terrain is realized.4.The paper analyzes the crack problem and popping phenomenon in the quadtree LOD algorithm,discusses and improves the crack treatment scheme under the restricted quadtree and the unrestricted quadtree,and proposes a level difference limitation algorithm for the restricted quadtree,which can only limit the level difference of the terrain in the visible region.A lot of experimental work has been done in this paper,and the experimental results verify the effectiveness of various schemes and improved algorithms proposed in this paper.Finally,based on these strategies and algorithms,a global terrain real-time rendering system is implemented,which is efficient and reliable,and can render the global terrain in real time.