Extrinsically smooth direction fields

Extrinsic - Zhiyang Huang (2016) ------------------------------------ This code implements the algorithm described in Huang Z, Ju T. Extrinsically smooth direction fields. Comput Graph(2016), http://dx.doi.org/10.1016/j.cag.2016.05.015i The basic function of this program is to compute extrinsically smooth direction fields “g” upon a curve, surface or volume while giving a references field “f”, such that “g” is orthogonal to “f”. In particular, the default setting of “f” for curve and surface are tangent field of the curve and normal field of the surface, respectively. The parameter-free initialization method based on least eigenvector problem and the Gauss–Seidel iterations, as described in the above paper, are implemented in this code and subjected to use. Currently the code is only tested on Mac OS X 10.10 or above, it should work at other platforms with minor modification.外蕴（Extrinsic）——黄志扬（Zhiyang Huang，2016） ------------------------------------ 本代码实现了下述论文中提出的算法： Huang Z, Ju T. 外蕴平滑方向场（Extrinsically smooth direction fields）. 《Comput Graph》，2016，http://dx.doi.org/10.1016/j.cag.2016.05.015i 本程序的核心功能为：在给定参考场"f"的前提下，于曲线、曲面或体域上计算外蕴平滑方向场"g"，使得"g"与"f"正交。具体而言，针对曲线与曲面场景，参考场"f"的默认设置分别为曲线的切向场与曲面的法向场。 本代码已实现上述论文中提及的、基于最小特征向量问题的无参数初始化方法，以及高斯-赛德尔（Gauss–Seidel）迭代算法，并可直接调用。 目前本代码仅在Mac OS X 10.10及以上版本中完成测试，若需在其他平台运行，仅需进行少量修改即可适配。