Arc

The ARC entity (DXF Reference) represents a circular arc, which is defined by the DXF attributes dxf.center, dxf.radius, dxf.start_angle and dxf.end_angle. The arc-curve goes always from dxf.start_angle to dxf.end_angle in counter-clockwise orientation around the dxf.extrusion vector, which is (0, 0, 1) by default and the usual case for 2D arcs. The ARC entity has OCS coordinates.

The helper tool ezdxf.math.ConstructionArc supports creating arcs from various scenarios, like from 3 points or 2 points and an angle or 2 points and a radius and the upright module can convert inverted extrusion vectors from (0, 0, -1) to (0, 0, 1) without changing the curve.

See also

Tutorial for Simple DXF Entities, section Arc
ezdxf.math.ConstructionArc
Object Coordinate System (OCS)
ezdxf.upright module

Subclass of	`ezdxf.entities.Circle`
DXF type	`'ARC'`
Factory function	`ezdxf.layouts.BaseLayout.add_arc()`
Inherited DXF attributes	Common graphical DXF attributes

Warning

Do not instantiate entity classes by yourself - always use the provided factory functions!

class ezdxf.entities.Arc

dxf.center: Center point of arc (2D/3D Point in OCS)

dxf.radius: Radius of arc (float)

dxf.start_angle: Start angle in degrees (float)

dxf.end_angle: End angle in degrees (float)

start_point: Returns the start point of the arc in WCS, takes the OCS into account.

end_point: Returns the end point of the arc in WCS, takes the OCS into account.

angles(num: int) → Iterator[float]: Yields num angles from start- to end angle in degrees in counter-clockwise orientation. All angles are normalized in the range from [0, 360).

flattening(sagitta: float) → Iterator[Vec3]: Approximate the arc by vertices in WCS, the argument sagitta defines the maximum distance from the center of an arc segment to the center of its chord.

transform(m: Matrix44) → Arc: Transform ARC entity by transformation matrix m inplace. Raises NonUniformScalingError() for non-uniform scaling.

to_ellipse(replace=True) → Ellipse

Convert the CIRCLE/ARC entity to an Ellipse entity.

Adds the new ELLIPSE entity to the entity database and to the same layout as the source entity.

Parameters:: replace – replace (delete) source entity by ELLIPSE entity if True

to_spline(replace=True) → Spline

Convert the CIRCLE/ARC entity to a Spline entity.

Adds the new SPLINE entity to the entity database and to the same layout as the source entity.

Parameters:: replace – replace (delete) source entity by SPLINE entity if True

construction_tool() → ConstructionArc: Returns the 2D construction tool ezdxf.math.ConstructionArc but the extrusion vector is ignored.

apply_construction_tool(arc: ConstructionArc) → Arc: Set ARC data from the construction tool ezdxf.math.ConstructionArc but the extrusion vector is ignored.