| 摘要 |
A collision of a moving object with another object in a 3D virtual world is efficiently determined in real time so that the technique is usable over a network. An object in the 3D virtual world is projected onto a 2D plane. The projection of the object is bounded by a two-sided edge cycle that is formed from a sequence of line segments having endpoints that are consecutively joined at an ordered series of vertices. One side, which is formed by a counterclockwise ordering of the line segments and their respective vertices, is characterized as "front facing." The other side is characterized as "back facing." Additionally, the front and back facing characterization of a side of the edge cycle is determined by the disposition of the moving object, i.e., the closest side of the edge cycle to the moving object is its back facing side. A path line segment is developed for the projection of a path of a moving object onto the 2D plane, and a path line equation is determined for the path line segment. The path line equation is employed to identify any positive to negative sign transition between consecutive vertices of a front facing line segment of the edge cycle. An edge cycle line equation is then evaluated with the endpoints of the path line segment for the moving object to determine if the path line segment has intersected the line segment of the edge cycle during a particular time period.
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