pythonocc基础使用：2.提取曲线上的点位信息或者曲面上的点位信息

桃扇骨 2022-04-04 11:15 641阅读 0赞

## **总目录** >> [PythonOCC入门进阶到实战][PythonOCC](目前已更新入门篇、基础篇和进阶篇) ##

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BRepLProp：（local property 局部性质）

*  These global functions compute the degree ofcontinuity of a curve built by concatenation of twoedges at their junction point.  
    BRepGProp ：（global property 全部性质）  
    \-Provides global functions to compute a shape’s globalproperties for lines, surfaces or volumes, and bringthem together with the global properties alreadycomputed for a geometric system.The global properties computed for a system are :- its mass（质量）,- its center of mass（质心）,- its matrix of inertia（惯性矩阵）,- its moment（惯性矩） about an axis,- its radius of gyration（回转半径） about an axis,- and its principal properties of inertia such as principal axis, principal moments, principal radius of gyration.

做cad开发，有一个很重要的目的就是识别曲线或者曲面的点位信息。  
用的主要函数是`breptools_UVBounds` 和`GeomLProp_SurfaceTool.D1`

for shape in shp: #只有选中的是shp中的部分，才跳入到下面循环
            face = topods_Face(shape)
            surface=BRep_Tool.Surface(face)
            global umax, umin, vmax, vmin
            Umin, Umax, Vmin, Vmax = breptools_UVBounds(face)
            umax = str(Umax)
            umin = str(Umin)
            vmax = str(Vmax)
            vmin = str(Vmin)
            #face2 = BRepAdaptor_Surface(face1).D1()
            p=gp_Pnt() #点
            D1U=gp_Vec() #一阶u
            D1V=gp_Vec() #一阶v
            GeomLProp_SurfaceTool.D1(surface,0.3,0.4,p,D1U,D1V)
            #此处可以返回p（也就是该点的位置信息），,D1U是指U的一阶导数，D1V是指V的一阶导数，通过U的一阶导数与V的一阶导数的叉乘可以得到该点的法向量

[PythonOCC]: https://blog.csdn.net/weixin_42755384/article/details/87893697