Abstract
Abstract. Summary: In recent years, with the development of the virtual reality technology and data acquisition technology, people increase the demand of GIS visualization. Especially accounting for occupying 70 percent of global area, and as a based environmental visualization, global ocean visualization is particularly important in some applications. This paper studies the global ocean visualization and modeling techniques under the framework of the WGS84 ellipsoid and achieves a method of rapid global ocean photorealistic rendering. The main research works are as follow: 1. In the height field modeling, with the law of statistical and spectral marine and Phillip wave spectrum, we can produce a single height map which considers the wind farm on the ocean wave magnitude of impact; 2. With ellipsoid rectangular grid mapping relationship, the single height map produced above will be mapped to the ellipsoid repeatedly, and achieve a goal of global ocean height field modeling; 3. With the conversion of screen space coordinate system and the rectangular spatial coordinate system, sampling points can be acquired by the view-dependent ellipsoid; 4. With the introduction of global bathymetric data, and came through the GPU for rapid sampling, so that we can get sampling points related to transparency and depth values to achieve a global ocean and land border processing.
Highlights
Using the above formula from the spatial Cartesian coordinate system to convert between geodetic coordinate system, high precision and speed
For the ellipsoid height field under the waves, there are two ways, one is the earth into a curved projection plane, on a plane to establish the entire height field; Another is the use of repeating textures to achieve height map
The results show that the rendering speed is associated with the grid resolution, when the grid resolution is small, the frame rate is larger, but not enough fidelity simulation; and when the grid resolution is bigger, better simulate realistic sense, but frame rate will drop, but this time there is noticeable pause and screen flicker
Summary
Real-time rendering with spherical ocean closely related, is the reference ellipsoid, which geodesy is defined as: "a certain parameter, positioning and orientation, and is used to represent a region of the Earth geoid ellipsoid 'reference mapping exercise ellipsoid has a very important role: the mathematical surfaces represent the Earth, a large number of measurement reference plane, the measurement and calculation of the reference plane vigorously paper WGS84(US, 2004)reference ellipsoid with the parameters provided by the geodetic coordinates completion (B , L, H) to the earth space Cartesian coordinates (X, Y, Z) conversion. should be noted that, since this model in building pyramids, geodetic coordinates are used to ensure that the data is the uniqueness of the original coordinates, and coordinate transformation in real-time rendering is done, so what kind of reference to use, does not affect the accuracy of the original data, and can be readily converted reference system, the conversion process is very simple, only need to modify the reference ellipsoid parameters can be related to this paper use the WGS84 reference ellipsoid, its main parameters are as follows: Long radius a 6378137.0m. Should be noted that, since this model in building pyramids, geodetic coordinates are used to ensure that the data is the uniqueness of the original coordinates, and coordinate transformation in real-time rendering is done, so what kind of reference to use, does not affect the accuracy of the original data, and can be readily converted reference system, the conversion process is very simple, only need to modify the reference ellipsoid parameters can be related to this paper use the WGS84 reference ellipsoid, its main parameters are as follows: Long radius a 6378137.0m. Using the above formula from the spatial Cartesian coordinate system to convert between geodetic coordinate system, high precision and speed
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