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Compute parabola from three points

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This commit is contained in:
wmayer 2012-10-22 15:55:39 +02:00
parent d50fb2ba06
commit ec3c79ad9c
2 changed files with 53 additions and 0 deletions
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8
src/Mod/Part/App/ParabolaPy.xml
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@ -14,6 +14,14 @@
<Author Licence="LGPL" Name="Werner Mayer" EMail="wmayer@users.sourceforge.net" />
<UserDocu>Describes a parabola in 3D space</UserDocu>
</Documentation>
<Methode Name="compute">
<Documentation>
<UserDocu>
compute(p1,p2,p3)
The three points must lie on a plane parallel to xy plane and must not be collinear
</UserDocu>
</Documentation>
</Methode>
<Attribute Name="Eccentricity" ReadOnly="true">
<Documentation>
<UserDocu>Returns 1. (which is the eccentricity of any parabola).</UserDocu>

45
src/Mod/Part/App/ParabolaPyImp.cpp
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@ -60,6 +60,51 @@ int ParabolaPy::PyInit(PyObject* args, PyObject* /*kwd*/)
return -1;
}
PyObject* ParabolaPy::compute(PyObject *args)
{
PyObject *p1, *p2, *p3;
if (!PyArg_ParseTuple(args, "O!O!O!",
&Base::VectorPy::Type,&p1,
&Base::VectorPy::Type,&p2,
&Base::VectorPy::Type,&p3))
return 0;
Base::Vector3d v1 = Py::Vector(p1,false).toVector();
Base::Vector3d v2 = Py::Vector(p2,false).toVector();
Base::Vector3d v3 = Py::Vector(p3,false).toVector();
Base::Vector3d c = (v1-v2) % (v3-v2);
double zValue = v1.z;
if (fabs(c.Length()) < 0.0001) {
PyErr_SetString(PyExc_Exception, "Points are collinear");
return 0;
}
Base::Matrix4D m;
Base::Vector3f v;
m[0][0] = v1.y * v1.y;
m[0][1] = v1.y;
m[0][2] = 1;
m[1][0] = v2.y * v2.y;
m[1][1] = v2.y;
m[1][2] = 1;
m[2][0] = v3.y * v3.y;
m[2][1] = v3.y;
m[2][2] = 1.0;
v.x = v1.x;
v.y = v2.x;
v.z = v3.x;
m.inverseGauss();
v = m * v;
double a22 = v.x;
double a10 = -0.5;
double a20 = v.y/2.0;
double a00 = v.z;
Handle_Geom_Parabola curve = Handle_Geom_Parabola::DownCast(getGeometryPtr()->handle());
curve->SetFocal(0.5*fabs(a10/a22));
curve->SetLocation(gp_Pnt((a20*a20-a22*a00)/(2*a22*a10), -a20/a22, zValue));
Py_Return;
}
Py::Float ParabolaPy::getEccentricity(void) const
{
Handle_Geom_Parabola curve = Handle_Geom_Parabola::DownCast(getGeometryPtr()->handle());