General Curves API mapping

[portnov]

In this issue I will try to outline a general API for all types of curves we are going to support.

Legend:

• :new: there is no such method in the base class yet, it has to be introduced to support features provided by one (or several) of backends.
• :construction: this method can and must be implemented in the base class by means by other (more basic) methods - there is a not-so-hard to implement numeric algorihtm
• :x: this method can not be implemented if the backend library does not support it (or it is too hard to implement it)
• :question: probably possible to implement without backend support, requires further investigation

General curves:

SvCurve method	Geomdl	FreeCAD	rhino3dm
evaluate(t)	evaluate_single(t)	value(t)	PointAt(t)
evaluate_array(ts)	:construction:	:construction:	:construction:
:new:: evaluate_even_t(n)	:construction:	discretize()	:construction:
:new:: evaluate_even_distance(n)	:construction:	discretize()	:construction:
calc_length	:construction:	length()	:construction:
tangent(t)	tangent()	tangent()	TangentAt()
tangent_array(ts)	:construction:	:construction:	:construction:
second_derivative(t)	derivatives(t,2)	derivative2At(t)	:construction:
second_derivative_array(ts)	:construction:	:construction:	:construction:
:new:: third_derivative(t)	derivatives(t,3)	derivative3At(t)	:construction:
third_derivative_array(ts)	:construction:	:construction:	:construction:
:new:: derivatives(n, t)	derivatives(t,n)	:construction:	:construction:
derivatives_array(n,ts)	:construction:	:construction:	:construction:
main_normal(t)	normal(t)	normal(t)	:construction:
main_normal_array(ts)	:construction:	:construction:	:construction:
binormal(t)	binormal(t)	:construction:	:construction:
binormal_array(ts)	:construction:	:construction:	:construction:
tangent_normal_binormal_array(ts)	:construction:	:construction:	:construction:
frame_array(ts)	:construction:	:construction:	:construction:
:new:: curvature(t)	:construction:	curvature(t)	CurvatureAt(t)
curvature_array(ts)	:construction:	:construction:	:construction:
torsion_array(ts)	:construction:	:construction:	:construction:
:new: intersect_curve	:question:	intersectCC()	:question:
:new: intersect_surface	:construction:	intersectCS()	:construction:
:new: ortho_project (implemented in sverchok_extra.utils.geom)	:construction:	parameter()	:construction:
:new: length_parameter (implemented in sverchok.utils.curve.SvCurveLengthSolver)	:construction:	parameterAtDistance()	:construction:
:new: to_nurbs	:construction: (trivial)	toNurbs()	:construction: (trivial)
:new: to_bspline	:construction: (trivial)	toBSpline()	:construction: (trivial)

[portnov]

NURBS / BSpline curves methods; :new: SvNurbsCurve will be a new abstract class, so all it's methods are new.

SvNurbsCurve method	Geomdl	FreeCAD	rhino3dm
classmethod approximate()	approximate_curve(points, degree, ctrlpts_count)	approximate(points, degree_min, degree_max, tolerance, continuity)	:x:
classmethod interpolate()	interpolate_curve(points, degree, centripetal)	interpolate(points, is_periodic, tolerance, initial_tangent, final_tangent, tangents, tangent_flags)	:x:
move_point()	:x:	movePoint(t, point, i1, i2)	:x:
is_planar()	:question: :	:question:	IsPlanar()