Design And Implementation Of The 3D Model Rendering System Based On Node Cluster

As a major open source 3D graphics engine,Open Scene Graph(OSG)is widely used in the field of geographic information system,visual simulation,virtual reality,scientific computing,three-dimensional reconstruction and so on.The OSG platform enables designers to create high-performance,cross-platform interactive graphics programs more quickly and easily.However,OSG platform still has the following two deficiencies.First,its data loading method has high requirements on memory capacity.When loading a massive data model,as the data volume increases rapidly,the memory space cannot be released in time and effectively,resulting in a sharp increase in the memory occupancy rate,which leads to a lack of fluency in the loading process of massive data.Thus it greatly affects the model rendering effects.Second,the OSG platform allows a limited number of data file types that can be loaded,such as the osg file and the ive file.These file types lack effective supports for the confidentiality of key data,which can easily lead to the leakage of key data,thus causing the security risks of the data model.Aiming at the problems existing in the current OSG platform,this thesis well designs and implements the 3D model rendering system based on node cluster.The system constructs node cluster as the basic unit of the 3D scene rendering,and uses the generated node cluster information to carry out the dynamic loading of 3D primitives,so that the 3D scene rendering effect becomes more smooth,and the memory utilization is also effectively improved.As the same time,binary data file types based on rvm format are supported in our system,and the confidentiality of key data is enhanced by the binary coding rules of rvm format data,which effectively expands the availability of the rendering system.The major work of this thesis includes three aspects as follows.(1)Requirements analysis and architecture design.In view of deficiencies in current OSG rendering system,such as high memory occupancy rate and poor data security,the functional and non-functional requirements of the 3D model rendering system proposed in this thesis are well analyzed,and the system architecture design is proposed as well.The system is divided into three functional subsystems: primitives management subsystem,node cluster construction subsystem and scene rendering subsystem.The function analysis and module division of each subsystem are carried out in detail,and relationship between each functional system is clarified.On this basis,the system architecture is designed and the requirements of non-functional attributes,such as security,are analyzed.(2)Key system functions design and implementation.The core system functions are designed in detail and the corresponding algorithms is proposed to implement these core functions.The rvm file parsing algorithm is used to realize the parsing function of file structure.The rvm geometry parameter generation algorithm and geometry property assembly are used to generate various geometry primitives flexibly and effectively.The node clustering algorithm based on space is used to achieve the node clusters generation function.The model file generation algorithm is used to realize the model export function.The Render Bin generation algorithm is used to realize the Render Bin generation function.The dynamic loading algorithm based on node cluster is used implement the dynamic loading function.(3)System function testing and rendering effect analysis.Detailed functional testing are performed towards each function points of our 3D model rendering system,which used to validate the correctness and usability of the system.On this basis,the dynamic loading function of graph metadata is analyzed in detail.By comparing the rendering effects between our system and the current OSG rendering system,we show that the method proposed in this thesis to optimize the memory usage by using node cluster could make the rendering effects more smooth when loading massive data model,and effectively improve the utilization of system memory.At last,this thesis illustrates that the model file used by our system could well guarantee the security of key data compared with other model file types.