Macro Draft Circle 3 Points 3D

Description
This macro creates a circle on 3 selected points in the space. The points can be objects such as cubes, cylinder, then selected coordinates will be the centre of these forms.



Use
Select 3 points, or forms in the 3D view and run the macro.

If the shape is a line, the coordinate will be the center of the line.

Limits
The order of selection of fear forms influencing the AXIS angle and reverse the inclination of the circle. In this case, reverse or change the order of selection of the shapes.

The coordinates X, Y, Z of value 0 or alignment not allowing not calculating, can return a division by zero error, and translated as "The three points are aligned"

Script

 * 1) -*- coding: utf-8 -*-
 * 2) Create a circle from 3 points selected on the X, Y, Z map
 * 3) 04/03/2013
 * 4) From http://en.wikipedia.org/wiki/Circumscribed_circle

from math import pi, asin import Draft, FreeCAD, FreeCADGui from FreeCAD import Base from PyQt4 import QtCore, QtGui

def errorDialog(msg): # Create a simple dialog QMessageBox # The first argument indicates the icon used: one of QtGui.QMessageBox.{NoIcon, Information, Warning, Critical, Question} diag = QtGui.QMessageBox(QtGui.QMessageBox.Critical,u"Error Message",msg) diag.setWindowModality(QtCore.Qt.ApplicationModal) diag.exec_

def affiche(x,y,z,r,angle): diag = QtGui.QMessageBox(QtGui.QMessageBox.Information,u"Coordinates",u"Coordinate X : "+str(x)+"\r\n"+u"Coordinate Y : "+str(y)+"\n"+u"Coordinate Z : "+str(z)+"\nRadius\t  : "+str(r)+"\nAngle\t   : "+str(angle)) diag.setWindowModality(QtCore.Qt.ApplicationModal) diag.setWindowModality(QtCore.Qt.NonModal) diag.exec_

sel = FreeCADGui.Selection.getSelection if len(sel)==3 : # Assignment of variables P1 = sel[0].Shape.BoundBox.Center P2 = sel[1].Shape.BoundBox.Center P3 = sel[2].Shape.BoundBox.Center
 * 1) objects selected
 * 1) If there are 3 selected points so...

P1P2 = (P2 - P1).Length P2P3 = (P3 - P2).Length P3P1 = (P1 - P3).Length

# Circle radius. l = ((P1 - P2).cross(P2 - P3)).Length try: #if l < 1e-8: #   errorDialog("The three points are aligned") r = P1P2 * P2P3 * P3P1 / 2 / l   except: errorDialog("The three points are aligned") else: # Sphere center. a = P2P3**2 * (P1 - P2).dot(P1 - P3) / 2 / l**2 b = P3P1**2 * (P2 - P1).dot(P2 - P3) / 2 / l**2 c = P1P2**2 * (P3 - P1).dot(P3 - P2) / 2 / l**2 P1.multiply(a) P2.multiply(b) P3.multiply(c) PC = P1 + P2 + P3

# Creation of a circle pl = Base.Placement v = (P1 - P2).cross(P3 - P2) v.normalize axis = Base.Vector(0, 0, 1).cross(v) angle = asin(axis.Length) * 180 / pi       axis.normalize pl = Base.Placement(PC, axis, angle) Draft.makeCircle(r, placement=pl, face=False, support=None) # Displays the result in the windows affiche((PC.x),(PC.y),(PC.z),r,angle) # Displays the result in the FreeCAD report view #FreeCAD.Console.PrintMessage("Coordinate X : "+str(PC.x)+"\n") #FreeCAD.Console.PrintMessage("Coordinate Y : "+str(PC.y)+"\n") #FreeCAD.Console.PrintMessage("Coordinate Z : "+str(PC.z)+"\n") #FreeCAD.Console.PrintMessage("Radius      : "+str(r)+"\n") #FreeCAD.Console.PrintMessage("Angle       : "+str(angle)+"\n") else: # If the condition is not met, repeat FreeCAD.Console.PrintError("Select 3 points and repeat\n")