Research On 3D Cloud Simulation Technology Based On Meteorological Data

As a natural phenomenon with a formation complex process,clouds pose a huge challenge to standard computer image generation techniques because clouds do not have well-defined surfaces and boundaries.In addition,the cloud contains varying degrees of translucency,and its crystal structure can change with time.Some existing cloud simulation methods,although producing good visual effects,rely on complex mathematical models.These models generate high computational costs due to single image output.Therefore,the research on efficient and realistic cloud simulation methods is one of the most challenging topics in the field of computer graphics.This thesis studies the rendering technology of cloud in natural scenes.Mainly from two aspects: cloud shape simulation and cloud illumination effect simulation.The main research work and results are as follows:1.The three-dimensional cloudscape is drawn by using the Ray Casting algorithm in the volume rendering method,in which the acceleration technique such as rasterization intersection and advanced light termination method is used to improve the rendering speed of the cloud scene.2.In this thesis,a method for random disturbance of cloud surface is proposed.The specific method is to generate random noise according to 3D Perlin function,and make it into texture,and add the texture to the sampling process to mix with the original texture in different proportions.By this method,the painted cloud surface is softer and the details are displayed better.3.In order to improve user's visual perception of the cloudscape drawn by Ray Casting algorithm,this thesis applies Phong illumination model and Blinn Phong illumination model to cloudscape respectively.Compared with the respective effect of the two model,we find that both of them enhance stereo perception of cloudscape but effects of them are too artistic and the realism is not strong.Therefore,a new illumination model are proposed by this thesis.this new illumination model that combines the Cook Torrance illumination with BRDF model,are applied to the drawing process of cloudscape.The model fully considers the influence of thematerial micro-plane on the illumination.Compared with the Phong and Blinn Phong illumination models,the new illumination model make cloudscape more realistic and richer in detail when the operating efficiency is not reduced.4.In the thesis,two methods of drawing based on image texture are proposed.Considering system efficiency,using Billboard bulletin board technology to draw large-scale cumulus scenes.Two improvements to the traditional Billboard technology are proposed.They are(1)considering randomness,propose a mechanism for randomly selecting cumulus texture maps;(2)combined with real meteorological data,according to the value on the position of which clouds to be placed is used to determine the intensity of the clouds near the position.The final cumulus scene is closer to the real situation and more abundant.This thesis studies the different rendering techniques of 3D clouds and develops a weather plugin on the existing 3D digital earth platform.Using the real-time detection of meteorological historical data,a variety of cloud scenes are drawn by improving the existing cloud drawing methods and some methods used to enhance the realism of the cloudscape.Experiments confirmed that the realistic effect of cloudscape is greatly improved.