| 摘要 |
A virtual terrain architecture and computer program product for employing a geocentric coordinate system, using a tessellated three-dimensional shape for representing a celestial body, and mapping terrain data to the tessellated three-dimensional shape is disclosed. In one embodiment, the methodology begins with a seed polyhedron such as an ellipsoid model. The seed ellipsoid is preferably composed of a plurality of triangle primitives. After selection of the seed ellipsoid, the ellipsoid is subdivided using tessellation. Each triangular element is subdivided into four sub-elements which are also triangular in shape. As the elements are further subdivided, the triangles of the ellipsoid model create a sphere that is representative of the earth or other celestial body. Tessellation continues until a desired resolution is reached for each triangular element. Once a sphere has been substantially formed, terrain data is mapped to the triangular elements and the data is converted to geocentric coordinates and stored in a database. Each triangular element is separately indexed according to the triangular elements name. By creating a geocentric representation, the earth's curvature and polar regions can be accurately represented. By using a tessellation process, tiling for the geocentric coordinate system is achieved. Thus, the tiles can be paged as discrete elements.
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