def test_rational_spline_from_circular_arc_has_expected_parameters():
arc = ConstructionArc(end_angle=90)
spline = rational_bspline_from_arc(end_angle=arc.end_angle)
assert spline.degree == 2
cpoints = spline.control_points
assert len(cpoints) == 3
assert cpoints[0].isclose((1, 0, 0))
assert cpoints[1].isclose((1, 1, 0))
assert cpoints[2].isclose((0, 1, 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_arc(arc)
assert spline.control_points == s2.control_points
end_angle=165,
dxfattribs={
"layer": "source arc",
"color": ezdxf.const.RED,
}
)
# create a SPLINE entity from ARC, in your scenario these are the source
# entities of your DXF document!
spline = msp.add_spline(dxfattribs={
"layer": "B-Spline",
"color": ezdxf.const.YELLOW,
})
# create a B-spline construction tool from ARC
arc_tool = arc.construction_tool()
bspline = BSpline.from_arc(arc_tool)
spline.apply_construction_tool(bspline)
# Recreate ARC from SPLINE, if you ASSUME or KNOW it is an ARC:
# for spline in msp.query("SPLINE):
# ...
# 1. get the B-spline construction tool from the SPLINE entity
bspline = spline.construction_tool()
max_t = bspline.max_t
# calculate 3 significant points and 2 check points of the SPLINE:
start, chk1, middle, chk2, end = bspline.points([
0, max_t * 0.25, max_t * 0.5, max_t * 0.75, max_t
])
# create an arc from 3 points:
# ------------------------------------------------------------------------------
# Create SPLINE from ARC
#
# The BSpline.from_arc() method creates a rational B-spline that is a perfect
# circular arc.
# ------------------------------------------------------------------------------
doc, msp = new_doc()
arc = msp.add_arc(
(0, 0),
radius=3,
start_angle=30,
end_angle=330,
dxfattribs={"layer": "ENTITY"},
)
s = BSpline.from_arc(arc.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_arc.dxf")
# ------------------------------------------------------------------------------
# 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(