Add ParabolicCenterArc function

docs/algebra_definition.rst

@@ -29,7 +29,7 @@ Objects and arithmetic
 
 :math:`B^2 := \lbrace` ``Sketch``, ``Rectangle``, ``Circle``, ``Ellipse``, ``Rectangle``, ``Polygon``, ``RegularPolygon``, ``Text``, ``Trapezoid``, ``SlotArc``, ``SlotCenterPoint``, ``SlotCenterToCenter``, ``SlotOverall`` :math:`\rbrace`
 
-:math:`B^1 := \lbrace` ``Curve``, ``Bezier``, ``FilletPolyline``, ``PolarLine``, ``Polyline``, ``Spline``, ``Helix``, ``CenterArc``, ``EllipticalCenterArc``, ``RadiusArc``, ``SagittaArc``, ``TangentArc``, ``ThreePointArc``, ``JernArc`` :math:`\rbrace`
+:math:`B^1 := \lbrace` ``Curve``, ``Bezier``, ``FilletPolyline``, ``PolarLine``, ``Polyline``, ``Spline``, ``Helix``, ``CenterArc``, ``EllipticalCenterArc``, ``ParabolicCenterArc``, ``RadiusArc``, ``SagittaArc``, ``TangentArc``, ``ThreePointArc``, ``JernArc`` :math:`\rbrace`
 
 with :math:`B^3 \subset C^3, B^2 \subset C^2` and :math:`B^1 \subset C^1`
 

docs/cheat_sheet.rst

@@ -23,6 +23,7 @@ Cheat Sheet
             | :class:`~objects_curve.CenterArc`
             | :class:`~objects_curve.DoubleTangentArc`
             | :class:`~objects_curve.EllipticalCenterArc`
+            | :class:`~objects_curve.ParabolicCenterArc`
             | :class:`~objects_curve.FilletPolyline`
             | :class:`~objects_curve.Helix`
             | :class:`~objects_curve.IntersectingLine`

docs/objects.rst

@@ -118,6 +118,13 @@ The following objects all can be used in BuildLine contexts. Note that
         +++
         Elliptical arc defined by center,  radii & angles
 
+    .. grid-item-card:: :class:`~objects_curve.ParabolicCenterArc`
+
+        .. image:: assets/parabolic_center_arc_example.svg
+
+        +++
+        Parabolic arc defined by vertex, focal length & angles
+
     .. grid-item-card:: :class:`~objects_curve.FilletPolyline`
 
         .. image:: assets/filletpolyline_example.svg

docs/objects_1d.py

@@ -125,6 +125,14 @@ svg.add_shape(elliptical_center_arc.line)
 svg.add_shape(dot.moved(Location(Vector((0, 0)))))
 svg.write("assets/elliptical_center_arc_example.svg")
 
+with BuildLine() as parabolic_center_arc:
+    ParabolicCenterArc((0, 0), 0.5, 60, 0)
+s = 100 / max(*parabolic_center_arc.line.bounding_box().size)
+svg = ExportSVG(scale=s)
+svg.add_shape(parabolic_center_arc.line)
+svg.add_shape(dot.moved(Location(Vector((0, 0)))))
+svg.write("assets/parabolic_center_arc_example.svg")
+
 with BuildLine() as helix:
     Helix(1, 3, 1)
 scene = Compound(helix.line) + Compound.make_triad(0.5)

src/build123d/__init__.py

@@ -88,6 +88,7 @@ __all__ = [
     "DoubleTangentArc",
     "EllipticalCenterArc",
     "EllipticalStartArc",
+    "ParabolicCenterArc",
     "FilletPolyline",
     "Helix",
     "IntersectingLine",

src/build123d/importers.py

@@ -287,6 +287,7 @@ def import_svg_as_buildline_code(
         "QuadraticBezier": ["Bezier", "start", "control", "end"],
         "Arc": [
             "EllipticalCenterArc",
+            "ParabolicCenterArc",
             # "EllipticalStartArc",
             "start",
             "end",

src/build123d/objects_curve.py

@@ -741,6 +741,61 @@ class EllipticalCenterArc(BaseEdgeObject):
         super().__init__(curve, mode=mode)
 
 
+class ParabolicCenterArc(BaseEdgeObject):
+    """Line Object: Parabolic Center Arc
+
+    Create a parabolic arc defined by a vertex point and focal length (distance from focus to vertex).
+
+    Args:
+        vertex (VectorLike): parabola vertex
+        focal_length (float): focal length the parabola (distance from the vertex to focus along the x-axis of plane)
+        start_angle (float, optional): arc start angle.
+            Defaults to 0.0
+        end_angle (float, optional): arc end angle.
+            Defaults to 90.0
+        rotation (float, optional): angle to rotate arc. Defaults to 0.0
+        angular_direction (AngularDirection, optional): arc direction.
+            Defaults to AngularDirection.COUNTER_CLOCKWISE
+        plane (Plane, optional): base plane. Defaults to Plane.XY
+        mode (Mode, optional): combination mode. Defaults to Mode.ADD
+    """
+
+    _applies_to = [BuildLine._tag]
+
+    def __init__(
+        self,
+        vertex: VectorLike,
+        focal_length: float,
+        start_angle: float = 0.0,
+        end_angle: float = 90.0,
+        rotation: float = 0.0,
+        angular_direction: AngularDirection = AngularDirection.COUNTER_CLOCKWISE,
+        mode: Mode = Mode.ADD,
+    ):
+        context: BuildLine | None = BuildLine._get_context(self)
+        validate_inputs(context, self)
+
+        vertex_pnt = WorkplaneList.localize(vertex)
+        if context is None:
+            parabola_workplane = Plane.XY
+        else:
+            parabola_workplane = copy_module.copy(
+                WorkplaneList._get_context().workplanes[0]
+            )
+        parabola_workplane.origin = vertex_pnt
+        curve = Edge.make_parabola(
+            focal_length=focal_length,
+            plane=parabola_workplane,
+            start_angle=start_angle,
+            end_angle=end_angle,
+            angular_direction=angular_direction,
+        ).rotate(
+            Axis(parabola_workplane.origin, parabola_workplane.z_dir.to_dir()), rotation
+        )
+
+        super().__init__(curve, mode=mode)
+
+
 class Helix(BaseEdgeObject):
     """Line Object: Helix
 

src/build123d/topology/one_d.py

@@ -88,7 +88,7 @@ from OCP.BRepOffsetAPI import BRepOffsetAPI_MakeOffset
 from OCP.BRepPrimAPI import BRepPrimAPI_MakeHalfSpace
 from OCP.BRepProj import BRepProj_Projection
 from OCP.BRepTools import BRepTools, BRepTools_WireExplorer
-from OCP.GC import GC_MakeArcOfCircle, GC_MakeArcOfEllipse
+from OCP.GC import GC_MakeArcOfCircle, GC_MakeArcOfEllipse, GC_MakeArcOfParabola
 from OCP.GCPnts import (
     GCPnts_AbscissaPoint,
     GCPnts_QuasiUniformDeflection,
@@ -151,6 +151,7 @@ from OCP.gp import (
     gp_Dir,
     gp_Dir2d,
     gp_Elips,
+    gp_Parab,
     gp_Pln,
     gp_Pnt,
     gp_Pnt2d,
@@ -2204,6 +2205,42 @@ class Edge(Mixin1D[TopoDS_Edge]):
 
         return ellipse
 
+    @classmethod
+    def make_parabola(
+        cls,
+        focal_length: float,
+        plane: Plane = Plane.XY,
+        start_angle: float = 0.0,
+        end_angle: float = 90.0,
+        angular_direction: AngularDirection = AngularDirection.COUNTER_CLOCKWISE,
+    ) -> Edge:
+        """make parabola
+
+        Makes an parabola centered at the origin of plane.
+
+        Args:
+            focal_length (float): focal length the parabola (distance from the vertex to focus along the x-axis of plane)
+            plane (Plane, optional): base plane. Defaults to Plane.XY.
+            start_angle (float, optional): Defaults to 0.0.
+            end_angle (float, optional): Defaults to 90.0.
+            angular_direction (AngularDirection, optional): arc direction.
+                Defaults to AngularDirection.COUNTER_CLOCKWISE.
+
+        Returns:
+            Edge: full or partial parabola
+        """
+        parabola_gp = gp_Parab(plane.to_gp_ax2(), focal_length)
+
+        parabola_geom = GC_MakeArcOfParabola(
+            parabola_gp,
+            start_angle * DEG2RAD,
+            end_angle * DEG2RAD,
+            angular_direction == AngularDirection.COUNTER_CLOCKWISE,
+        ).Value()
+        parabola = cls(BRepBuilderAPI_MakeEdge(parabola_geom).Edge())
+
+        return parabola
+
     @classmethod
     def make_helix(
         cls,