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Line (line segment) is defined with its two vertices.
line = curveset.add( Line(number, pt1, pt2) )
Arc of circle is defined using three points, as shown on the figure.
arc = curveset.add( Arc(number, pt1, pt2, pt3) )
spl = curveset.add( CubicSpline(number, [pt1, pt2, pt3, pt4]) ) spl.useLsTangent() # tangents are calculated # using local reconstruction [DEFAULT] spl.useLittTangents() # tangents are calculated # using Litt/Beckers lectures
To close a spline, the first and last points of the list must be the same.
spl = CubicSpline(number, [pt1, pt2, pt3, pt4, ..., pt1])
or, if the curve is defined based on a mesh, the mesh must be chosen closed.
spl = CubicSpline(number, obj)
obj is a meshed object.
A circle is defined with its center and radius (this function is only defined in the $z=0$ plane)
circ2d = curset.add( Circle(number, pt1, radius) )
The orientation of the circle can be inverted (and so will its tangent and normal used for contact):
A Non-Uniform Rational Basis Spline (N.U.R.B.S.) is defined as:
nur = curset.add( NurbsCurve(number) ) nur.setDegree(degree) nur.push(pt1); nur.pushWeight(weight1) nur.push(pt2); nur.pushWeight(weight2) nur.pushKnot(knot1) nur.pushKnot(knot2)
| ||curve number|
| ||degré de la coube|
| ||knot vector|
| ||Boolean to determine whether the Nurb is closed|
| ||GObject support of a topology (curve,wire,group)|
If a curve cannot be defined with the functions above, it can be programmed in python, to avoid having to enter Metafor source code.
PythonCurve is the object to use. It is a regular curve,
.push() is used to add points, and it possesses four functions that can be parametrized.
setEval(fct) is used to defined the evaluation python function.
setLen() respectively define the tangent, its derivative and the curvilinear abscissa. The function
setEval(fct) is required to mesh the curve, when the other three are used for contact.
Once this new curve is defined, it can be shaped as the already existing one, with a class. For example, if a parabola has just been defined (cfr.
toolbox.curves), it can be used quite simply in a test case (cfr.
from toolbox.curves import Parabola parab = curset.add(Parabola(1, pt1, pt6, pt2))
These lines create a parabola of user number 1, based on the three previously defined point pt1, pt6 and pt2.