Abstract: In most STL model slicing algorithms, because of the losses of accuracies in floating-point operations, some wrong intersection lines generally existed when computing intersection lines of the triangle facets and the tangent planes in the case of one edge of a triangle are very close to the tangent planes, even some errors can not be repaired. This dissertation proposes a slicing algorithm based on a local topology to solve such problems. Extract all facets caused errors to establish a topology, then replace intersection lines with the projections of near edges. This algorithm can eliminate wrongs of lost and redundant edges of the slice contour due to errors of floating-point operations. The experiment results show that the algorithm can get a correct slice contour through simple calculations without any repairs.

Key words: rapid prototyping, slice contour, triangle facet, floating-point operation, approximate parallel edges

摘要： 在对STL模型分层求交线过程中，针对三角面片的边与切平面很接近时，浮点运算引起的精度损失可能导致的错误交线问题，提出一种基于STL模型局部拓扑的分层算法。将所有可能引起错误交线的三角面片提取出来，建立拓扑结构，以接近切平面的边在切平面的投影替代交线，消除了由于浮点运算误差导致的轮廓线缺边和重边的错误。实验结果表明，该算法在计算出交线段集后不需要再进行修复，简单连接后就能得出正确的切片轮廓线。

关键词: 快速成型, 切片轮廓线, 三角面片, 浮点运算, 近似平行边