Spline¶

The SPLINE entity (DXF Reference) is a 3D curve, all coordinates have to be 3D coordinates even if the spline is just a 2D planar curve.

The spline curve is defined by control points, knot values and weights. The control points establish the spline, the various types of knot vector determines the shape of the curve and the weights of rational splines define how strong a control point influences the shape.

A SPLINE can be created just from fit points - knot values and weights are optional (tested with AutoCAD 2010). If you add additional data, be sure you know what you do, because invalid data may invalidate the whole DXF file.

The function ezdxf.math.fit_points_to_cad_cv() calculates control vertices from given fit points. This control vertices define a cubic B-spline which matches visually the SPLINE entities created by BricsCAD and AutoCAD from fit points.

Factory Functions¶

Basic spline entity	`add_spline()`
Spline control frame from fit points	`add_spline_control_frame()`
Open uniform spline	`add_open_spline()`
Closed uniform spline	`add_closed_spline()`
Open rational uniform spline	`add_rational_spline()`
Closed rational uniform spline	`add_closed_rational_spline()`

class ezdxf.entities.Spline¶

All points in WCS as (x, y, z) tuples

dxf.degree¶: Degree of the spline curve (int).

dxf.flags¶

Bit coded option flags, constants defined in ezdxf.lldxf.const:

dxf.flags	Value	Description
CLOSED_SPLINE	1	Spline is closed
PERIODIC_SPLINE	2
RATIONAL_SPLINE	4
PLANAR_SPLINE	8
LINEAR_SPLINE	16	planar bit is also set

dxf.n_knots¶: Count of knot values (int), automatically set by ezdxf (read only)

dxf.n_fit_points¶: Count of fit points (int), automatically set by ezdxf (read only)

dxf.n_control_points¶: Count of control points (int), automatically set by ezdxf (read only)

dxf.knot_tolerance¶: Knot tolerance (float); default is 1e-10

dxf.fit_tolerance¶: Fit tolerance (float); default is 1e-10

dxf.control_point_tolerance¶: Control point tolerance (float); default is 1e-10

dxf.start_tangent¶: Start tangent vector as 3D vector in WCS

dxf.end_tangent¶: End tangent vector as 3D vector in WCS

closed¶: True if spline is closed. A closed spline has a connection from the last control point to the first control point. (read/write)

control_points¶: VertexArray of control points in WCS.

fit_points¶: VertexArray of fit points in WCS.

knots¶: Knot values as array.array('d').

weights¶: Control point weights as array.array('d').

control_point_count() → int¶: Count of control points.

fit_point_count() → int¶: Count of fit points.

knot_count() → int¶: Count of knot values.

construction_tool() → ezdxf.math.bspline.BSpline¶: Returns the construction tool ezdxf.math.BSpline.

apply_construction_tool(s) → ezdxf.entities.spline.Spline¶: Apply SPLINE data from a BSpline construction tool or from a geomdl.BSpline.Curve object.

flattening(distance: float, segments: int = 4) → Iterator[ezdxf.math._vector.Vec3]¶

Adaptive recursive flattening. The argument segments is the minimum count of approximation segments between two knots, if the distance from the center of the approximation segment to the curve is bigger than distance the segment will be subdivided.

Parameters:	distance – maximum distance from the projected curve point onto the segment chord. segments – minimum segment count between two knots

set_open_uniform(control_points: Sequence[Union[Sequence[float], ezdxf.math._vector.Vec2, ezdxf.math._vector.Vec3]], degree: int = 3) → None¶: Open B-spline with a uniform knot vector, start and end at your first and last control points.

set_uniform(control_points: Sequence[Union[Sequence[float], ezdxf.math._vector.Vec2, ezdxf.math._vector.Vec3]], degree: int = 3) → None¶: B-spline with a uniform knot vector, does NOT start and end at your first and last control points.

set_closed(control_points: Sequence[Union[Sequence[float], ezdxf.math._vector.Vec2, ezdxf.math._vector.Vec3]], degree=3) → None¶: Closed B-spline with a uniform knot vector, start and end at your first control point.

set_open_rational(control_points: Sequence[Union[Sequence[float], ezdxf.math._vector.Vec2, ezdxf.math._vector.Vec3]], weights: Sequence[float], degree: int = 3) → None¶: Open rational B-spline with a uniform knot vector, start and end at your first and last control points, and has additional control possibilities by weighting each control point.

set_uniform_rational(control_points: Sequence[Union[Sequence[float], ezdxf.math._vector.Vec2, ezdxf.math._vector.Vec3]], weights: Sequence[float], degree: int = 3) → None¶: Rational B-spline with a uniform knot vector, does NOT start and end at your first and last control points, and has additional control possibilities by weighting each control point.

set_closed_rational(control_points: Sequence[Union[Sequence[float], ezdxf.math._vector.Vec2, ezdxf.math._vector.Vec3]], weights: Sequence[float], degree: int = 3) → None¶: Closed rational B-spline with a uniform knot vector, start and end at your first control point, and has additional control possibilities by weighting each control point.

transform(m: ezdxf.math._matrix44.Matrix44) → ezdxf.entities.spline.Spline¶: Transform the SPLINE entity by transformation matrix m inplace.

classmethod from_arc(entity: ezdxf.entities.dxfgfx.DXFGraphic) → ezdxf.entities.spline.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!

Subclass of	`ezdxf.entities.DXFGraphic`
DXF type	`'SPLINE'`
Factory function	see table below
Inherited DXF attributes	Common graphical DXF attributes
Required DXF version	DXF R2000 (`'AC1015'`)