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# Copyright (c) 2022, Manfred Moitzi
# License: MIT License
import pathlib
import ezdxf
from ezdxf import colors
from ezdxf.gfxattribs import GfxAttribs
from ezdxf.math import intersect_polylines_2d, Vec2
CWD = pathlib.Path("~/Desktop/Outbox").expanduser()
if not CWD.exists():
CWD = pathlib.Path(".")
# ------------------------------------------------------------------------------
# This example shows how to calculate intersection points of arbitrary 2d
# polylines, an ellipse and a spline in this example.
#
# docs: https://ezdxf.mozman.at/docs/math/core.html#ezdxf.math.intersect_polylines_2d
# ------------------------------------------------------------------------------
ENTITIES = "ENTITIES"
INTERSECTION_POINTS = "INTERSECTION_POINTS"
CURVE_APPROXIMATIONS = "CURVE_APPROXIMATIONS"
def main():
doc = ezdxf.new()
doc.layers.add(ENTITIES, color=colors.YELLOW)
doc.layers.add(INTERSECTION_POINTS, color=colors.RED)
doc.layers.add(CURVE_APPROXIMATIONS, color=colors.CYAN)
msp = doc.modelspace()
ellipse = msp.add_ellipse(
center=(0, 0),
major_axis=(3, 0),
ratio=0.5,
dxfattribs=GfxAttribs(layer=ENTITIES),
)
fit_points = [(-4, -4), (-2, -1), (2, 1), (4, 4)]
spline = msp.add_spline_control_frame(
fit_points, dxfattribs=GfxAttribs(layer=ENTITIES)
)
# create 2D polylines from the DXF entities:
p1 = Vec2.list(ellipse.flattening(distance=0.001))
p2 = Vec2.list(spline.flattening(distance=0.001))
# add the 2D polylines as reference graphics:
msp.add_lwpolyline(p1, dxfattribs=GfxAttribs(layer=CURVE_APPROXIMATIONS))
msp.add_lwpolyline(p2, dxfattribs=GfxAttribs(layer=CURVE_APPROXIMATIONS))
# the intersection calculation between these polylines:
res = intersect_polylines_2d(p1, p2)
# add intersection points as CIRCLE entities:
for point in res:
msp.add_circle(
center=point,
radius=0.1,
dxfattribs=GfxAttribs(layer=INTERSECTION_POINTS),
)
doc.set_modelspace_vport(height=10)
doc.saveas(CWD / "intersect_ellipse_and_spline.dxf")
if __name__ == "__main__":
main()
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