def from_arc(cls, entity: 'DXFGraphic') -> 'Spline':
""" Create a new SPLINE entity from a CIRCLE, ARC or ELLIPSE entity.
The new SPLINE entity has no owner, no handle, is not stored in
the entity database nor assigned to any layout!
"""
dxftype = entity.dxftype()
if dxftype == 'ELLIPSE':
ellipse = cast('Ellipse', entity).construction_tool()
elif dxftype == 'CIRCLE':
ellipse = ConstructionEllipse.from_arc(
center=entity.dxf.get('center', NULLVEC),
radius=abs(entity.dxf.get('radius', 1.0)),
extrusion=entity.dxf.get('extrusion', Z_AXIS),
)
elif dxftype == 'ARC':
ellipse = ConstructionEllipse.from_arc(
center=entity.dxf.get('center', NULLVEC),
radius=abs(entity.dxf.get('radius', 1.0)),
extrusion=entity.dxf.get('extrusion', Z_AXIS),
start_angle=entity.dxf.get('start_angle', 0),
end_angle=entity.dxf.get('end_angle', 360))
else:
raise TypeError('CIRCLE, ARC or ELLIPSE entity required.')
spline = Spline.new(dxfattribs=entity.graphic_properties(),
doc=entity.doc)
s = BSpline.from_ellipse(ellipse)
spline.dxf.degree = s.degree
spline.dxf.flags = Spline.RATIONAL
spline.control_points = s.control_points
spline.knots = s.knots()
spline.weights = s.weights()
return spline
def test_rational_spline_from_elliptic_arc_has_expected_parameters():
ellipse = ConstructionEllipse(
center=(1, 1),
major_axis=(2, 0),
ratio=0.5,
start_param=0,
end_param=math.pi / 2,
)
spline = rational_bspline_from_ellipse(ellipse)
assert spline.degree == 2
cpoints = spline.control_points
assert len(cpoints) == 3
assert cpoints[0].isclose((3, 1, 0))
assert cpoints[1].isclose((3, 2, 0))
assert cpoints[2].isclose((1, 2, 0))
weights = spline.weights()
assert len(weights) == 3
assert weights[0] == 1.0
assert weights[1] == math.cos(math.pi / 4)
assert weights[2] == 1.0
# as BSpline constructor()
s2 = BSpline.from_ellipse(ellipse)
assert spline.control_points == s2.control_points
def from_arc(cls, entity: "DXFGraphic") -> "Spline":
"""Create a new SPLINE entity from a CIRCLE, ARC or ELLIPSE entity.
The new SPLINE entity has no owner, no handle, is not stored in
the entity database nor assigned to any layout!
"""
dxftype = entity.dxftype()
if dxftype == "ELLIPSE":
ellipse = cast("Ellipse", entity).construction_tool()
elif dxftype == "CIRCLE":
ellipse = ConstructionEllipse.from_arc(
center=entity.dxf.get("center", NULLVEC),
radius=abs(entity.dxf.get("radius", 1.0)),
extrusion=entity.dxf.get("extrusion", Z_AXIS),
)
elif dxftype == "ARC":
ellipse = ConstructionEllipse.from_arc(
center=entity.dxf.get("center", NULLVEC),
radius=abs(entity.dxf.get("radius", 1.0)),
extrusion=entity.dxf.get("extrusion", Z_AXIS),
start_angle=entity.dxf.get("start_angle", 0),
end_angle=entity.dxf.get("end_angle", 360),
)
else:
raise TypeError("CIRCLE, ARC or ELLIPSE entity required.")
spline = Spline.new(dxfattribs=entity.graphic_properties(),
doc=entity.doc)
s = BSpline.from_ellipse(ellipse)
spline.dxf.degree = s.degree
spline.dxf.flags = Spline.RATIONAL
spline.control_points = s.control_points # type: ignore
spline.knots = s.knots() # type: ignore
spline.weights = s.weights() # type: ignore
return spline
# ------------------------------------------------------------------------------
# Create SPLINE from ELLIPSE
#
# The BSpline.from_ellipse() method creates a rational B-spline that is a
# perfect elliptic arc.
# ------------------------------------------------------------------------------
doc, msp = new_doc()
ellipse = msp.add_ellipse(
(0, 0),
major_axis=(3, 0),
ratio=0.7,
start_param=math.radians(30),
end_param=math.radians(330),
dxfattribs={"layer": "ENTITY"},
)
s = BSpline.from_ellipse(ellipse.construction_tool())
spline = msp.add_spline(dxfattribs={"layer": "SPLINE"})
spline.apply_construction_tool(s)
add_control_frame(spline)
add_control_polyline(spline)
save(DIR / "spline_from_ellipse.dxf")
# ------------------------------------------------------------------------------
# Open unclamped SPLINE by control points
# ------------------------------------------------------------------------------
doc, msp = new_doc()
spline = msp.add_spline(dxfattribs={"layer": "SPLINE"})
spline.set_uniform(points)