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

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

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