Research On Transfer Function In Volume Rendering Of 3D Underwater Acoustic Data

The visualization of underwater acoustic data is the important means for human to explore the marine world.It has a wide range of applications in the exploration of marine resources,the exploration of seabed topography and the field of fisheries.With the development of parallel processing technology such as GPU,direct volume rendering technology with high rendering quality has become the main way to realize visualization,and the design of transfer function,as one of the key technologies,has always been the focus of attention.In order to further improve the visualization effect of underwater acoustic data,this paper makes an in-depth study on the design of transfer function in volume rendering according to the characteristics of underwater acoustic data.The main research work and results are as follows:Firstly,in view of the poor effect of the existing transfer function on the classification of the water layer and the ground layer of the underwater acoustic data,a transfer function method for volume rendering of underwater acoustic data based on 3-D non-under-sampling Brushlet transform is proposed.Based on the advantages of the three-dimensional Brushlet transform in detecting and capturing the high Vickers and directional texture information in the volume data,the texture features of the underwater acoustic data are extracted from the volume blocks with different directional coefficients of the non-under-sampling Brushlet transform by combining the gray level co-occurrence matrix,and then the data classification is completed by using the fuzzy c-means clustering method.Finally,according to the classification results,opacity and color mapping functions are designed to realize visualization.The experimental results show that compared with other methods,this method has better classification ability,and can effectively filter out the impurities in the underwater acoustic data,strengthen the boundary information,so as to enhance the rendering effect.Secondly,aiming at the disadvantage of traditional target detection algorithm for underwater acoustic data,an improved adaptive threshold three-dimensional region growing algorithm is proposed to detect the target of underwater acoustic data,and it is applied to the design of underwater acoustic data transfer function.The algorithm can automatically select the most appropriate initial seed point in the underwater acoustic data,and can grow according to the growth The rules can adaptively change the threshold value and achieve the best region growth effect;then combined with three-dimensional mathematical morphology,the targets in the water layer and the ground layer of the underwater acoustic data are detected and classified;finally,according to the classification results,the corresponding opacity and color mapping rules are designed for the water non target background area,the ground non target background area and the target object respectively,and call VTK for visualization.The experimental results show that this method can effectively segment the target object and the background area,and gets a relatively ideal rendering effect.