三维实体重建时投影图数据的预处理

介绍三维实体重建过程中投影图数据的处理算法，绘制同一图层的图形时，视图分割算法添加平行于两坐标轴的辅助直线，移动辅助线使其将三视图分割开来；对基于同一坐标系的投影三视图数据，推出从设备坐标系到各视图坐标系的转换公式并为其设计了转换算法，该算法求出三视图坐标系共有的原点，再根据视图分割的结果将每一图形元素转换到新的坐标系统中；隐含点的求取算法先判断同一视图中图元间的位置关系，再求出它们之间的公共点，这些点将用于线框搜索过程中，以上算法处理的投影图点线数据分别存入点线链表中。

The Pretreatment of Orthographic Views Data in 3D Reconstruction

Some algorithms for pretreating the input data of orthographic views in 3D solid reconstruction are presented. For views being drawn in the same graphic layer, auxiliary lines parallel to the coordinate axes are added and progressively relocated until the three orthographic views are separated from each other. Since the graphic entities are originally presented in the device coordinate system, transformation matrices relative to the new origin of separated views are needed to transform each entity to the new local coordinate system. Tangent point and crossing point between line segments are referred to as implicit points. They should be explicitly marked out to help the tracing of wireframe loops. All the classified points and line segments are stored in the corresponding chained lists.