Macro EdgesToArc

File:Text-x-python FaceToSketch
Description
Replaces the selected Edges by a circular Arc if possible. Useful for restoring discretized arcs. Author: Jreinhardt
Author
Jreinhardt
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Macro Version
1.0
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Manchmal hat man mit einem Wire zu tun, bei dem ein Kreisbogen aus vielen kleinen geraden Segmenten aufgebaut ist. Dieser Fall tritt häufig auf, wenn man mit Dateien arbeitet, die mit anderen Programmen erstellt wurden. Mit diesem Macro kann man solche diskretisierten Kreisbögen in echte Kreisbögen umwandeln. Das führt zu kleineren und aufgeräumteren Dateien.

To use this macro, you have to break down the wire into individual edges using the Draft Downgrade function. Then just select the segments that you want to replace by an circular arc and execute the macro. You need at least two segments.

The macro will check whether the segments all lie on a common circle and will abort if this is not the case. Otherwise it will create the arc and remove the segments.

Because of small inaccuracies in the calculations, the Draft Upgrade function can sometimes fail to recombine the other edges and the arcs back into a wire. In this case the SuperWire macro provides a more robust way to do this.

import Draft
import FreeCADGui, FreeCAD
from FreeCAD import Base, Console
from math import atan2, pi, fabs

#This macro replaces a number of edges approximating a circular arc by a proper circular arc.
#It might be necessary to use the superwire macro to recombine the edges back to a wire, because of small errors in the calculations.

sel = FreeCADGui.Selection.getSelection()
if len(sel) < 2:
    Console.PrintError("Too few edges are selected\n")
edges = [s.Shape for s in sel]

start_vertices = []
end_vertices = []
for edge in edges:
    start_vertices.append(edge.Vertexes[0].Point)
    end_vertices.append(edge.Vertexes[1].Point)
vertices = start_vertices + end_vertices

start,end,middle = None,None,None

#find start and end points
for edge in edges:
    is_start = True
    is_end = True
    for point in end_vertices:
        if edge.Vertexes[0].Point.distanceToPoint(point) < 1e-8:
            is_start = False

    for point in start_vertices:
        if edge.Vertexes[1].Point.distanceToPoint(point) < 1e-8:
            is_end = False
    if is_start:
        start = edge.Vertexes[0].Point
    if is_end:
        end = edge.Vertexes[1].Point

#find middle point, at least not too far away from the middle

for v in vertices:
    ratio = v.distanceToPoint(start)/v.distanceToPoint(end)
    if ratio > 0.5 and ratio < 2.:
        middle = v
        break

if middle is None:
    Console.PrintError("Could not find suitable middle point\n")

arc = Part.ArcOfCircle(start,middle,end)

#Check circularity
circular = True
for v in vertices:
    if fabs(v.distanceToPoint(arc.Center) - arc.Radius) > 1e-6:
        Console.PrintError("Edges do not approximate a circular arc\n")
        circular = False
        break

if circular:
        Part.show(arc.toShape())
        for shape in sel:
            FreeCAD.ActiveDocument.removeObject(shape.Name)