Spline

class ezdxf.render.Spline(points: Iterable[UVec] | None = None, segments: int = 100)

This class can be used to render B-splines into DXF R12 files as approximated Polyline entities. The advantage of this class over the R12Spline class is, that this is a real 3D curve, which means that the B-spline vertices do have to be located in a flat plane, and no UCS class is needed to place the curve in 3D space.

See also

The newer BSpline class provides the advanced vertex interpolation method flattening().

__init__(points: Iterable[UVec] | None = None, segments: int = 100)
Parameters:

  • points – spline definition points

  • segments – count of line segments for approximation, vertex count is segments + 1

subdivide(segments: int = 4) → None

Calculate overall segment count, where segments is the sub-segment count, segments = 4, means 4 line segments between two definition points e.g. 4 definition points and 4 segments = 12 overall segments, useful for fit point rendering.

Parameters:

segments – sub-segments count between two definition points

render_as_fit_points(layout: BaseLayout, degree: int = 3, method: str = 'chord', dxfattribs: dict | None = None) → None

Render a B-spline as 2D/3D Polyline, where the definition points are fit points.

Parameters:

  • layout – BaseLayout object

  • degree – degree of B-spline (order = degree + 1)

  • method – “uniform”, “distance”/”chord”, “centripetal”/”sqrt_chord” or “arc” calculation method for parameter t

  • dxfattribs – DXF attributes for Polyline

render_open_bspline(layout: BaseLayout, degree: int = 3, dxfattribs=None) → None

Render an open uniform B-spline as 3D Polyline. Definition points are control points.

Parameters:

  • layout – BaseLayout object

  • degree – degree of B-spline (order = degree + 1)

  • dxfattribs – DXF attributes for Polyline

render_uniform_bspline(layout: BaseLayout, degree: int = 3, dxfattribs=None) → None

Render a uniform B-spline as 3D Polyline. Definition points are control points.

Parameters:

  • layout – BaseLayout object

  • degree – degree of B-spline (order = degree + 1)

  • dxfattribs – DXF attributes for Polyline

render_closed_bspline(layout: BaseLayout, degree: int = 3, dxfattribs=None) → None

Render a closed uniform B-spline as 3D Polyline. Definition points are control points.

Parameters:

  • layout – BaseLayout object

  • degree – degree of B-spline (order = degree + 1)

  • dxfattribs – DXF attributes for Polyline

render_open_rbspline(layout: BaseLayout, weights: Iterable[float], degree: int = 3, dxfattribs=None) → None

Render a rational open uniform BSpline as 3D Polyline. Definition points are control points.

Parameters:

  • layout – BaseLayout object

  • weights – list of weights, requires a weight value (float) for each definition point.

  • degree – degree of B-spline (order = degree + 1)

  • dxfattribs – DXF attributes for Polyline

render_uniform_rbspline(layout: BaseLayout, weights: Iterable[float], degree: int = 3, dxfattribs=None) → None

Render a rational uniform B-spline as 3D Polyline. Definition points are control points.

Parameters:

  • layout – BaseLayout object

  • weights – list of weights, requires a weight value (float) for each definition point.

  • degree – degree of B-spline (order = degree + 1)

  • dxfattribs – DXF attributes for Polyline

render_closed_rbspline(layout: BaseLayout, weights: Iterable[float], degree: int = 3, dxfattribs=None) → None

Render a rational B-spline as 3D Polyline. Definition points are control points.

Parameters:

  • layout – BaseLayout object

  • weights – list of weights, requires a weight value (float) for each definition point.

  • degree – degree of B-spline (order = degree + 1)

  • dxfattribs – DXF attributes for Polyline

R12Spline

class ezdxf.render.R12Spline(control_points: Iterable[UVec], degree: int = 2, closed: bool = True)

DXF R12 supports 2D B-splines, but Autodesk do not document the usage in the DXF Reference. The base entity for splines in DXF R12 is the POLYLINE entity. The spline itself is always in a plane, but as any 2D entity, the spline can be transformed into the 3D object by elevation and extrusion (OCS, UCS).

This way it was possible to store the spline parameters in the DXF R12 file, to allow CAD applications to modify the spline parameters and rerender the B-spline afterward again as polyline approximation. Therefore, the result is not better than an approximation by the Spline class, it is also just a POLYLINE entity, but maybe someone need exact this tool in the future.

__init__(control_points: Iterable[UVec], degree: int = 2, closed: bool = True)
Parameters:

  • control_points – B-spline control frame vertices

  • degree – degree of B-spline, only 2 and 3 is supported

  • closed – True for closed curve

render(layout: BaseLayout, segments: int = 40, ucs: UCS | None = None, dxfattribs=None) → Polyline

Renders the B-spline into layout as 2D Polyline entity. Use an UCS to place the 2D spline in the 3D space, see approximate() for more information.

Parameters:

  • layout – BaseLayout object

  • segments – count of line segments for approximation, vertex count is segments + 1

  • ucs – UCS definition, control points in ucs coordinates.

  • dxfattribs – DXF attributes for Polyline

approximate(segments: int = 40, ucs: UCS | None = None) → list[UVec]

Approximate the B-spline by a polyline with segments line segments. If ucs is not None, ucs defines an UCS, to transform the curve into OCS. The control points are placed xy-plane of the UCS, don’t use z-axis coordinates, if so make sure all control points are in a plane parallel to the OCS base plane (UCS xy-plane), else the result is unpredictable and depends on the CAD application used to open the DXF file - it may crash.

Parameters:

  • segments – count of line segments for approximation, vertex count is segments + 1

  • ucs – UCS definition, control points in ucs coordinates

Returns:

list of vertices in OCS as Vec3 objects

Bezier

class ezdxf.render.Bezier

Render a bezier curve as 2D/3D Polyline.

The Bezier class is implemented with multiple segments, each segment is an optimized 4 point bezier curve, the 4 control points of the curve are: the start point (1) and the end point (4), point (2) is start point + start vector and point (3) is end point + end vector. Each segment has its own approximation count.

See also

The new ezdxf.path package provides many advanced construction tools based on the Path class.

start(point: UVec, tangent: UVec) → None

Set start point and start tangent.

Parameters:

  • point – start point

  • tangent – start tangent as vector, example: (5, 0, 0) means a horizontal tangent with a length of 5 drawing units

append(point: UVec, tangent1: UVec, tangent2: UVec | None = None, segments: int = 20)

Append a control point with two control tangents.

Parameters:

  • point – control point

  • tangent1 – first tangent as vector “left” of the control point

  • tangent2 – second tangent as vector “right” of the control point, if omitted tangent2 = -tangent1

  • segments – count of line segments for the polyline approximation, count of line segments from the previous control point to the appended control point.

render(layout: BaseLayout, force3d: bool = False, dxfattribs=None) → None

Render Bezier curve as 2D/3D Polyline.

Parameters:

  • layout – BaseLayout object

  • force3d – force 3D polyline rendering

  • dxfattribs – DXF attributes for Polyline

EulerSpiral

class ezdxf.render.EulerSpiral(curvature: float = 1)

Render an euler spiral as a 3D Polyline or a Spline entity.

This is a parametric curve, which always starts at the origin (0, 0).

__init__(curvature: float = 1)
Parameters:

curvature – Radius of curvature

render_polyline(layout: BaseLayout, length: float = 1, segments: int = 100, matrix: Matrix44 | None = None, dxfattribs=None)

Render curve as Polyline.

Parameters:

  • layout – BaseLayout object

  • length – length measured along the spiral curve from its initial position

  • segments – count of line segments to use, vertex count is segments + 1

  • matrix – transformation matrix as Matrix44

  • dxfattribs – DXF attributes for Polyline

Returns:

Polyline

render_spline(layout: BaseLayout, length: float = 1, fit_points: int = 10, degree: int = 3, matrix: Matrix44 | None = None, dxfattribs=None)

Render curve as Spline.

Parameters:

  • layout – BaseLayout object

  • length – length measured along the spiral curve from its initial position

  • fit_points – count of spline fit points to use

  • degree – degree of B-spline

  • matrix – transformation matrix as Matrix44

  • dxfattribs – DXF attributes for Spline

Returns:

Spline

Random Paths

Random path generators for testing purpose.

ezdxf.render.random_2d_path(steps: int = 100, max_step_size: float = 1.0, max_heading: float = math.pi / 2, retarget: int = 20) → Iterable[Vec2]

Returns a random 2D path as iterable of Vec2 objects.

Parameters:

  • steps – count of vertices to generate

  • max_step_size – max step size

  • max_heading – limit heading angle change per step to ± max_heading/2 in radians

  • retarget – specifies steps before changing global walking target

ezdxf.render.random_3d_path(steps: int = 100, max_step_size: float = 1.0, max_heading: float = math.pi / 2.0, max_pitch: float = math.pi / 8.0, retarget: int = 20) → Iterable[Vec3]

Returns a random 3D path as iterable of Vec3 objects.

Parameters:

  • steps – count of vertices to generate

  • max_step_size – max step size

  • max_heading – limit heading angle change per step to ± max_heading/2, rotation about the z-axis in radians

  • max_pitch – limit pitch angle change per step to ± max_pitch/2, rotation about the x-axis in radians

  • retarget – specifies steps before changing global walking target