Pythonocc/Opencascade |通过点沿直线创建管道，剖面不会改变正常

Question

我的最终目标如下：

我有一个庞大的点数据集，表示零件将如何逐层 3D 打印。我需要通过这些点创建一条线并沿着这条线挤出一个圆（因此重建零件，因为它将在稍后打印）。

我最初尝试做样条曲线，但是这试图创建一条平滑的线并且根本不遵循这些点。我尝试更改 minDeg 和 maxDeg 选项，但这仍然不足以创建我需要的实际曲线。

See this result for the spline

See here the actual path (the above spline is one of the infill parts)

所以我尝试一次只在两点之间创建样条曲线，然后在创建连线时将它们全部添加在一起。这看起来很有希望，因为现在我确实得到了实际的尖角和穿过精确点的线。然而，现在当我尝试沿着它挤出时，挤出轮廓的法线不会随着线的角度而改变。

This is what happens with the last thing I tried

我花了最后 4 天时间解决这个问题，尝试了很多论坛和问题，但感觉完全迷失在 pythonocc (opencascade) 的世界里。

我的代码如下：

from __future__ import print_function

from OCC.gp import gp_Pnt, gp_Ax2, gp_Dir, gp_Circ
from OCC.GeomAPI import GeomAPI_PointsToBSpline
from OCC.TColgp import TColgp_Array1OfPnt
from OCC.BRepBuilderAPI import BRepBuilderAPI_MakeEdge,         
BRepBuilderAPI_MakeWire, BRepBuilderAPI_MakeFace
from OCC.BRepOffsetAPI import BRepOffsetAPI_MakePipe

from OCC.Display.SimpleGui import init_display
display, start_display, add_menu, add_function_to_menu = init_display()

def pipe():
# the bspline path, must be a wire
# This will later be in a for loop but this is merely to validate the method         
using three different points.

array = TColgp_Array1OfPnt(1,2)
makeWire = BRepBuilderAPI_MakeWire()

point1 = gp_Pnt(0,0,0)
point2 = gp_Pnt(0,0,1)
array.SetValue(1, point1)
array.SetValue(2, point2)
spline = GeomAPI_PointsToBSpline(array).Curve()
edge = BRepBuilderAPI_MakeEdge(spline).Edge()

makeWire.Add(edge)

point1 = gp_Pnt(0, 0, 1)
point2 = gp_Pnt(0, 1, 2)
array.SetValue(1, point1)
array.SetValue(2, point2)
spline = GeomAPI_PointsToBSpline(array).Curve()
edge = BRepBuilderAPI_MakeEdge(spline).Edge()

makeWire.Add(edge)

point1 = gp_Pnt(0, 1, 2)
point2 = gp_Pnt(0, 2, 2)
array.SetValue(1, point1)
array.SetValue(2, point2)
spline = GeomAPI_PointsToBSpline(array).Curve()
edge = BRepBuilderAPI_MakeEdge(spline).Edge()

makeWire.Add(edge)

makeWire.Build()
wire = makeWire.Wire()

# the bspline profile. Profile mist be a wire/face
point = gp_Pnt(0,0,0)
dir = gp_Dir(0,0,1)
circle = gp_Circ(gp_Ax2(point,dir), 0.2)
profile_edge = BRepBuilderAPI_MakeEdge(circle).Edge()
profile_wire = BRepBuilderAPI_MakeWire(profile_edge).Wire()
profile_face = BRepBuilderAPI_MakeFace(profile_wire).Face()

# pipe
pipe = BRepOffsetAPI_MakePipe(wire, profile_face).Shape()

display.DisplayShape(profile_edge, update=False)
display.DisplayShape(wire, update=True)
display.DisplayShape(pipe, update=True)

if __name__ == '__main__':
pipe()
start_display()

Answer 1

虽然线的边缘相连，但过渡不平滑。 BrepOffsetAPI_MakePipe:

Constructs a pipe by sweeping the shape Profile along the wire Spine. The angle made by the spine with the profile is maintained along the length of the pipe. Warning Spine must be G1 continuous; that is, on the connection vertex of two edges of the wire, the tangent vectors on the left and on the right must have the same direction, though not necessarily the same magnitude.

可以找到另一个连续性描述here，我们需要相切（G1）。如果两条相邻曲线的端点不相切，则扫掠将无法保持相同的角度（由脊柱与轮廓形成）。

最简单的解决办法是切断管道。

def pipe(point1, point2):
    makeWire = BRepBuilderAPI_MakeWire()
    edge = BRepBuilderAPI_MakeEdge(point1, point2).Edge()
    makeWire.Add(edge)
    makeWire.Build()
    wire = makeWire.Wire()

    dir = gp_Dir(point2.X() - point1.X(), point2.Y() - point1.Y(), point2.Z() - point1.Z())
    circle = gp_Circ(gp_Ax2(point1,dir), 0.2)
    profile_edge = BRepBuilderAPI_MakeEdge(circle).Edge()
    profile_wire = BRepBuilderAPI_MakeWire(profile_edge).Wire()
    profile_face = BRepBuilderAPI_MakeFace(profile_wire).Face()
    pipe = BRepOffsetAPI_MakePipe(wire, profile_face).Shape()
    display.DisplayShape(pipe, update=True)

if __name__ == '__main__':
    pipe(gp_Pnt(0,0,0), gp_Pnt(0,0,1))
    pipe(gp_Pnt(0,0,1), gp_Pnt(0,1,2))     
    pipe(gp_Pnt(0,1,2), gp_Pnt(0,2,2))
    start_display()

我们可以添加球体来弥合间隙。

from OCC.BRepPrimAPI import BRepPrimAPI_MakeSphere

def sphere(centre, radius):
    sphere = BRepPrimAPI_MakeSphere (centre, radius).Shape()
    display.DisplayShape(sphere, update=True)

def pipe(point1, point2):
    ...

if __name__ == '__main__':
    pipe(gp_Pnt(0,0,0), gp_Pnt(0,0,1))
    sphere(gp_Pnt(0,0,1), 0.2)
    pipe(gp_Pnt(0,0,1), gp_Pnt(0,1,2))     
    sphere(gp_Pnt(0,1,2), 0.2)
    pipe(gp_Pnt(0,1,2), gp_Pnt(0,2,2))
    start_display()

或者，您可以实现圆角算法，例如 ChFi2d Class 提供的算法。鉴于激光打印上下文和算法的平面特征，我已将点映射到 xy 平面。

from OCC.ChFi2d import ChFi2d_AnaFilletAlgo

def filletEdges(ed1, ed2):
    radius = 0.3
    f = ChFi2d_AnaFilletAlgo()
    f.Init(ed1,ed2,gp_Pln())
    f.Perform(radius)
    return f.Result(ed1, ed2)

def pipe():
    # the points
    p1 = gp_Pnt(0,0,0)
    p2 = gp_Pnt(0,1,0)
    p3 = gp_Pnt(1,2,0)
    p4 = gp_Pnt(2,2,0)
    # the edges
    ed1 = BRepBuilderAPI_MakeEdge(p1,p2).Edge()
    ed2 = BRepBuilderAPI_MakeEdge(p2,p3).Edge()
    ed3 = BRepBuilderAPI_MakeEdge(p3,p4).Edge()
    # inbetween
    fillet12 = filletEdges(ed1, ed2)
    fillet23 = filletEdges(ed2, ed3) 
    # the wire
    makeWire = BRepBuilderAPI_MakeWire()
    makeWire.Add(ed1)
    makeWire.Add(fillet12)
    makeWire.Add(ed2)
    makeWire.Add(fillet23)
    makeWire.Add(ed3)
    makeWire.Build()
    wire = makeWire.Wire()
    # the pipe
    dir = gp_Dir(0,1,0)
    circle = gp_Circ(gp_Ax2(p1,dir), 0.2)
    profile_edge = BRepBuilderAPI_MakeEdge(circle).Edge()
    profile_wire = BRepBuilderAPI_MakeWire(profile_edge).Wire()
    profile_face = BRepBuilderAPI_MakeFace(profile_wire).Face()
    pipe = BRepOffsetAPI_MakePipe(wire, profile_face).Shape()
    display.DisplayShape(pipe, update=True)

if __name__ == '__main__':
    pipe()
    start_display()

Pythonocc/Opencascade |通过点沿直线创建管道，剖面不会改变正常

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