PythonOCC基础使用：建模——倒角倒圆（二维+三维）

参考文献：

https://github.com/LiHonJun/pythonocc-demos/tree/master/examples
倒角倒圆：
倒圆倒角常用在制造业中的零件，通过将物体的棱角换为多边或者圆球形状以减小应力集中。应用CAD对该类零件建模时，便需要在线面交汇处进行修正这些对象，常常考虑使用“倒角”、“倒圆”的功能从而一次性处理对象以简化步骤。“倒角”命令在二维平面中可以用来选中形成角的两条线，形成多边角，三维空间中同理；“倒圆”命令则可以在二维平面中选中形成角的两条线并将该直线角快速修正为圆角，三维空间中则能够形成圆球形角。

AUTO CAD中圆角的形成
实现方法：
在实现二维平面的“倒圆”功能时，pythonocc提供有ChFi2d_AnaFilletAlgo的方法将所选角进行倒圆处理、同时在三维空间中的模型也能够通过BRepFilletAPI_MakeFillet的方法来实现。
chfi2d允许modify chamfer，在之前的基础上更改数字，然后重新生成，特别符合人的操作过程。
二维倒圆：

pythonocc 二维平面倒圆

from OCC.Core.gp import gp_Pnt, gp_Pln
from OCC.Core.ChFi2d import ChFi2d_AnaFilletAlgo
from OCC.Core.BRepBuilderAPI import BRepBuilderAPI_MakeEdge
from OCC.Extend.ShapeFactory import make_wire
from OCC.Display.SimpleGui import init_display
display,start_display, add_menu,add_functionto_menu = init_display()
# Defining the points
p1 = gp_Pnt(0, 0, 0)
p2 = gp_Pnt(5, 5, 0)
p3 = gp_Pnt(-5,5, 0)
# Making the edges
ed1 = BRepBuilderAPI_MakeEdge(p3, p2).Edge()
ed2 = BRepBuilderAPI_MakeEdge(p2, p1).Edge()
#Making the 2dFillet
f = ChFi2d_AnaFilletAlgo()
f.Init(ed1, ed2, gp_Pln())
radius = 1.0
f.Perform(radius)
fillet2d = f.Result(ed1, ed2)
# Create and display a wire
w = make_wire([ed1, fillet2d, ed2])
display.DisplayShape(w)
start_display()

三维倒圆：

pythonocc 三维空间倒圆

import sys
from math import cos, pi
from OCC.Core.BRepAlgoAPI import BRepAlgoAPI_Fuse
from OCC.Core.BRepFilletAPI import BRepFilletAPI_MakeFillet
from OCC.Core.BRepPrimAPI import BRepPrimAPI_MakeBox, BRepPrimAPI_MakeCylinder
from OCC.Display.SimpleGui import init_display
from OCC.Core.TColgp import TColgp_Array1OfPnt2d
from OCC.Core.gp import gp_Ax2, gp_Pnt, gp_Dir, gp_Pnt2d
from OCC.Extend.TopologyUtils import TopologyExplorer
display, start_display, add_menu, add_function_to_menu = init_display()
def fillet(event=None):
    Box = BRepPrimAPI_MakeBox(gp_Pnt(-400, 0, 0), 200, 230, 180).Shape()
    fillet_ = BRepFilletAPI_MakeFillet(Box)
    # Add fillet on each edge
    for e in TopologyExplorer(Box).edges():
        fillet_.Add(20, e)
    blendedBox = fillet_.Shape()
    P1 = gp_Pnt(250, 150, 75)
    S1 = BRepPrimAPI_MakeBox(300, 200, 200).Shape()
    S2 = BRepPrimAPI_MakeBox(P1, 120, 180, 70).Shape()
    Fuse = BRepAlgoAPI_Fuse(S1, S2)
    FusedShape = Fuse.Shape()
    fill = BRepFilletAPI_MakeFillet(FusedShape)
    for e in TopologyExplorer(FusedShape).edges():
        fill.Add(e)
    for i in range(1, fill.NbContours() + 1):
        length = fill.Length(i)
        Rad = 0.15 * length
        fill.SetRadius(Rad, i, 1)
    blendedFusedSolids = fill.Shape()
    display.EraseAll()
    display.DisplayShape(blendedBox)
    display.DisplayShape(blendedFusedSolids)
    display.FitAll()
def variable_filleting(event=None):
    display.EraseAll()
    # Create Box
    Box = BRepPrimAPI_MakeBox(200, 200, 200).Shape()
    # Fillet
    Rake = BRepFilletAPI_MakeFillet(Box)
    ex = TopologyExplorer(Box).edges()
    next(ex)
    next(ex)
    next(ex)
    Rake.Add(8, 50, next(ex))
    Rake.Build()
    if Rake.IsDone():
        evolvedBox = Rake.Shape()
        display.DisplayShape(evolvedBox)
    else:
        print("Rake not done.")
    # Create Cylinder
    Cylinder = BRepPrimAPI_MakeCylinder(gp_Ax2(gp_Pnt(-300, 0, 0), gp_Dir(0, 0, 1)), 100, 200).Shape()
    fillet_ = BRepFilletAPI_MakeFillet(Cylinder)
    TabPoint2 = TColgp_Array1OfPnt2d(0, 20)
    for i in range(0, 20):
        Point2d = gp_Pnt2d(i * 2 * pi / 19, 60 * cos(i * pi / 19 - pi / 2) + 10)
        TabPoint2.SetValue(i, Point2d)
    exp2 = TopologyExplorer(Cylinder).edges()
    fillet_.Add(TabPoint2, next(exp2))
    fillet_.Build()
    if fillet_.IsDone():
        LawEvolvedCylinder = fillet_.Shape()
        display.DisplayShape(LawEvolvedCylinder)
    else:
        print("fillet not done.")  ## TODO : fillet not done
    P = gp_Pnt(350, 0, 0)
    Box2 = BRepPrimAPI_MakeBox(P, 200, 200, 200).Shape()
    afillet = BRepFilletAPI_MakeFillet(Box2)
    TabPoint = TColgp_Array1OfPnt2d(1, 6)
    P1 = gp_Pnt2d(0., 8.)
    P2 = gp_Pnt2d(0.2, 16.)
    P3 = gp_Pnt2d(0.4, 25.)
    P4 = gp_Pnt2d(0.6, 55.)
    P5 = gp_Pnt2d(0.8, 28.)
    P6 = gp_Pnt2d(1., 20.)
    TabPoint.SetValue(1, P1)
    TabPoint.SetValue(2, P2)
    TabPoint.SetValue(3, P3)
    TabPoint.SetValue(4, P4)
    TabPoint.SetValue(5, P5)
    TabPoint.SetValue(6, P6)
    exp = TopologyExplorer(Box2).edges()
    next(exp)
    next(exp)
    next(exp)
    afillet.Add(TabPoint, next(exp))
    afillet.Build()
    if afillet.IsDone():
        LawEvolvedBox = afillet.Shape()
    else:
        print("aFillet not done.")
        display.DisplayShape(LawEvolvedBox)
    display.FitAll()
def exit(event=None):
    sys.exit()
if __name__ == '__main__':
    add_menu('topology fillet operations')
    add_function_to_menu('topology fillet operations', fillet)
    add_function_to_menu('topology fillet operations', variable_filleting)
    add_function_to_menu('topology fillet operations', exit)
    start_display()