Real-time Volume Rendering Method Of Water Quality Change Data Based On Ray Casting Algorithm

Three-dimensional water quality model is a mathematical description of water quality change law,which can be used to simulate and predict water quality,and is of great significance to water pollution management and prevention.However,the existing visualization of water quality change data has some problems,such as low dimension,low rendering efficiency,poor real-time,poor interactivity and so on,which can not meet the needs of efficient simulation and real-time interactive analysis of water quality change.In view of the above problems,this paper plans to study the key technologies of real-time volume rendering of water quality change data based on ray casting algorithm,and select case areas,develop prototype systems,and carry out experimental analysis.The main research results and specific work of this paper are as follows:(1)The construction method of spatio-temporal voxel model based on water quality change data is proposed.Firstly,the water quality change data and volume data format are introduced.Secondly,according to the characteristics of water quality change data and volume data,the spatial range of data is divided with voxels as the smallest spatial unit,and the mapping relationship between attribute values and color values is established by unifying the spatio-temporal reference,thus constructing the spatio-temporal voxel model;Finally,the octree index construction and coding method based on voxel model is studied,and the data organization is optimized.(2)An efficient volume rendering method for water quality change simulation based on ray casting algorithm is proposed.Firstly,the basic principle of ray casting algorithm is introduced,and the general idea of efficient volume rendering of water quality change data is expounded Secondly,according to the spatial range and voxel resolution of spatio-temporal voxel model,the bounding box and volume texture are constructed adaptively Then,the key technologies of water quality change volume rendering based on ray casting algorithm are studied from the aspects of projection ray direction and crossing distance calculation,texture resampling,transfer function classification and ray synthesis Finally,the optimization and acceleration method of volume rendering with blank voxel jumping and ray termination in advance is studied.(3)Develop prototype system and carry out case experiment analysis.According to the above research results,based on nodejs and threejs framework,a prototype system was designed and developed,and the three-dimensional water quality model data of Chaohu Lake was selected for experimental analysis.The case area is tested and analyzed.In this paper,using nodejs and threejs framework,the prototype system is developed with the simulated data of three-dimensional water quality model of Chaohu Lake as experimental data,and the experimental analysis is carried out.Experimental results show that the spatio-temporal voxel model of water quality data constructed by this method can support volume rendering of water quality change data,and the average rendering efficiency is above 120 frames /s,which meets the requirements of real-time rendering and interactive analysis.