关键词: OpenGL 三维拾取 三维地形 二维输入设备 三维坐标 图形交互

Abstract:

A picking method to any point in a 3-D relief map based on OpenGL is presented in this paper. In the orthoprojection model, the total relief map is di vided into many uniform fields. First, it is judged that the point made by a 2-D input device is included by which field in the 3 D relief map. Second, it filters rigorously each graphics unit in the selected field, in order to judge which graphics unit is exactly selected by the input point. Third, acc ording to the vertex value of the selected graphics unit, the third dimensional value, which is corresponding to the 2-D input device, is gained precise ly. Finally, the true 3-D coordinate of any selected point is fed back so as to realize the function of graphic alternation

Key words: OpenGL, 3-D picking ;3-D relief map, 2-D input device ;3-D coordinate;graphics alternation