FreeCAD-macros

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#
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# Creates a parametric Rectellipse
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# (c) fcaponi78
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#
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#
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from __future__ import division
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__Comment__ = 'Creates a parametric approximation of a rectellipse'
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__Web__ = 'http://freecadweb.org/wiki/Macro_Rectellipse'
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__Wiki__ = 'http://freecadweb.org/wiki/Macro_Rectellipse'
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__Icon__ = ""
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__Help__ = 'Run, zoom fit, and change parameters'
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__Author__ = 'fcaponi78, shoogen and other contributors'
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__Version__ = 0.1
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__Status__ = 'alpha'
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__Requires__ = ''
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import FreeCAD
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from FreeCAD import Part
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from FreeCAD import Vector
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class RectEllipseFeature:
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    def __init__(self, obj):
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        """Add the properties: a, b, s, createFace"""
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        obj.addProperty('App::PropertyLength', 'a', 'Rectellipse',
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                        'Horizontal radius').a = 16.0
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        obj.addProperty('App::PropertyLength', 'b', 'Rectellipse',
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                        'Vertical radius').b = 9.0
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        obj.addProperty('App::PropertyFloat', 's', 'Rectellipse',
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                        'Squareness (0=ellipse, 1=rectangle)').s = 0.2
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        obj.addProperty('App::PropertyBool', 'createFace', 'Rectellipse',
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                        'true => face; false => wire').createFace = True
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        obj.Proxy = self
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    def onChanged(self, feature, prop):
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        if prop in ['a',  'b', 's', 'createFace']:
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            self.execute(feature)
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    def execute(self, feature):
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        r1 = feature.a
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        r2 = feature.b
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        if feature.s < 0:
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            feature.s = 0
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        elif feature.s > 1:
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            feature.s = 1
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        z = 0.0
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        # TODO: tweak p, so that the curve is the exact definition of a
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        # rectellipse (if possible).
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        p = 1.0
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        # NURBS knots weigts.
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        if feature.s > 0.9999999:
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            # If larger than 1e7, we obtain a rhombus.
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            w = 1e7
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        else:
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            w = 2 ** 0.5 / 2.0 / (1 - feature.s ** p)
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        # TODO: use a real rectangle if feature.s close to 1.
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        curve = Part.BSplineCurve()
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        curve.setPeriodic()
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        curve.increaseDegree(2)
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        # 5 knots, 8 poles
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        curve.insertKnots([i / 4 for i in (1, 2, 3)], [2] * 3)
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        curve.setPole(1, Vector(0, -r2, z), 1)
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        curve.setPole(2, Vector(-r1, -r2, z), w)
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        curve.setPole(3, Vector(-r1, 0, z), 1)
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        curve.setPole(4, Vector(-r1, r2, z), w)
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        curve.setPole(5, Vector(0, r2, z), 1)
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        curve.setPole(6, Vector(r1, r2, z), w)
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        curve.setPole(7, Vector(r1, 0, z), 1)
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        curve.setPole(8, Vector(r1, -r2, z), w)
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        if feature.createFace:
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            feature.Shape = Part.Face(Part.Wire(curve.toShape()))
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        else:
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            feature.Shape = curve.toShape()
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def makeRectellipseFeature():
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    doc = FreeCAD.activeDocument()
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    if doc is None:
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        doc = FreeCAD.newDocument()
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        if doc is None:
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            return
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    obj = doc.addObject('Part::FeaturePython', 'RectEllipseFeature')
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    obj.Label = 'RectEllipse'
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    RectEllipseFeature(obj)
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    obj.ViewObject.Proxy = 0
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if __name__ == "__main__":
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    makeRectellipseFeature()
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