Research On Visualization Technology Of Ocean Flow Field Data

The flow field visualization has always been a hot research direction of Visualization in Scientific Computing.The flow field visualization is a technology that uses computer graphics technology to map abstract and incomprehensible flow field data into intuitive images and display them on the screen.For human beings,the ocean is a closely linked ecological environment,and for countries,it is a space field with strategic position.Therefore,the research on visualization technology of ocean flow data can effectively understand the internal laws of the ocean,improve the utilization efficiency of marine resources and better protect the marine environment,which is of great significance to promote the construction and development of marine science.This dissertation introduces the current study status and methods of ocean flow data visualization technology in detail,mainly focusing on texture visualization methods based on line integral convolution,streamline visualization methods and particle system methods.The main work and innovations of this dissertation are as follows:(1)Aiming at the problem of how to improve the speed of streamline calculation in the process of line integral convolution,a line integral convolution enhancement algorithm of improved streamline generation is proposed.In this dissertation,the information entropy of the flow field is used to quantify the change degree of the flow field.The simple Euler method and the long integration step are used in the stable region,and the fourth-order Runge-Kutta method and the small integration step are used in the region of drastic change.Under the premise of ensuring the image quality of LIC results,the method of this dissertation has improved the calculation efficiency of the algorithm.(2)Aiming at the problem that the basic LIC can only show the direction of the flow field and cannot express the strength of the flow field,this dissertation studies the color-enhanced LIC algorithm.The color mapping effect is improved by using the cumulative distribution function transformation.For the problem that the image isdark after the fusion of the LIC texture with the color mapping result,the grayscale texture of the LIC result is histogram equalized firstly,then the secondary LIC is used to improve the contrast,and finally a fixed value is added to the grayscale value which makes the fusion result more clear and bright.The OLIC algorithm based on sparse noise is implemented,combined with color mapping,so that the visualization results can clearly express the direction of the flow field and the strength of the flow field.(3)A dynamic distance streamline placement algorithm based on information entropy is proposed.Based on the information entropy of the flow field,the interval between streamline is changed dynamicly.The area with large information entropy has smaller streamline interval,and the area with small information entropy has larger streamline interval.The streamline density of the important area in the flow field is larger which can prevent lossing the important details.The streamline density of the unimportant area in the flow field is small which can improve the visualization efficiency.The streamline color enhancement can express more flow field information.(4)The dynamic visualization method of ocean flow field data based on particle system is studied and improved.The problem of too long particle trajectory in low view angle and too short particle trajectory in high view angle is solved by using height and speed to controlling the particle motion step size.Using a particle generation strategy based on screen coordinates,the particles are generated in the screen coordinate system and then them are converted to latitude and longitude coordinates,which solves the problem of sparse particles density in the screen as the viewpoint is drawn closer.Finally,based on the above research content,a data visualization system of ocean flow field is designed and implemented on the 3D earth platform,to show the effect of different visualization methods for ocean flow field data.