Spline¶

class
ezdxf.render.
Spline
(points: Iterable[Vertex] = None, segments: int = 100)¶ This class can be used to render Bsplines into DXF R12 files as approximated
Polyline
entities. The advantage of this class over theR12Spline
class is, that this is a real 3D curve, which means that the Bspline 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 methodflattening()
.
__init__
(points: Iterable[Vertex] = 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 subsegment 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 – subsegments count between two definition points

render_as_fit_points
(layout: BaseLayout, degree: int = 3, method: str = 'chord', dxfattribs: dict = None) → None¶ Render a Bspline as 2D/3D
Polyline
, where the definition points are fit points.2D spline vertices uses:
add_polyline2d()
3D spline vertices uses:
add_polyline3d()
 Parameters
layout –
BaseLayout
objectdegree – degree of Bspline (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: dict = None) → None¶ Render an open uniform Bspline as 3D
Polyline
. Definition points are control points. Parameters
layout –
BaseLayout
objectdegree – degree of Bspline (order = degree + 1)
dxfattribs – DXF attributes for
Polyline

render_uniform_bspline
(layout: BaseLayout, degree: int = 3, dxfattribs: dict = None) → None¶ Render a uniform Bspline as 3D
Polyline
. Definition points are control points. Parameters
layout –
BaseLayout
objectdegree – degree of Bspline (order = degree + 1)
dxfattribs – DXF attributes for
Polyline

render_closed_bspline
(layout: BaseLayout, degree: int = 3, dxfattribs: dict = None) → None¶ Render a closed uniform Bspline as 3D
Polyline
. Definition points are control points. Parameters
layout –
BaseLayout
objectdegree – degree of Bspline (order = degree + 1)
dxfattribs – DXF attributes for
Polyline

render_open_rbspline
(layout: BaseLayout, weights: Iterable[float], degree: int = 3, dxfattribs: dict = None) → None¶ Render a rational open uniform BSpline as 3D
Polyline
. Definition points are control points. Parameters
layout –
BaseLayout
objectweights – list of weights, requires a weight value (float) for each definition point.
degree – degree of Bspline (order = degree + 1)
dxfattribs – DXF attributes for
Polyline

render_uniform_rbspline
(layout: BaseLayout, weights: Iterable[float], degree: int = 3, dxfattribs: dict = None) → None¶ Render a rational uniform Bspline as 3D
Polyline
. Definition points are control points. Parameters
layout –
BaseLayout
objectweights – list of weights, requires a weight value (float) for each definition point.
degree – degree of Bspline (order = degree + 1)
dxfattribs – DXF attributes for
Polyline

render_closed_rbspline
(layout: BaseLayout, weights: Iterable[float], degree: int = 3, dxfattribs: dict = None) → None¶ Render a rational Bspline as 3D
Polyline
. Definition points are control points. Parameters
layout –
BaseLayout
objectweights – list of weights, requires a weight value (float) for each definition point.
degree – degree of Bspline (order = degree + 1)
dxfattribs – DXF attributes for
Polyline

R12Spline¶

class
ezdxf.render.
R12Spline
(control_points: Iterable[Vertex], degree: int = 2, closed: bool = True)¶ DXF R12 supports 2D Bsplines, 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 Bspline 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[Vertex], degree: int = 2, closed: bool = True)¶  Parameters
control_points – Bspline control frame vertices
degree – degree of Bspline, only 2 and 3 is supported
closed –
True
for closed curve

render
(layout: BaseLayout, segments: int = 40, ucs: UCS = None, dxfattribs: dict = None) → Polyline¶ Renders the Bspline into layout as 2D
Polyline
entity. Use anUCS
to place the 2D spline in the 3D space, seeapproximate()
for more information. Parameters
layout –
BaseLayout
objectsegments – 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) → List[Vertex]¶ Approximate the Bspline by a polyline with segments line segments. If ucs is not
None
, ucs defines anUCS
, to transformed the curve into OCS. The control points are placed xyplane of the UCS, don’t use zaxis coordinates, if so make sure all control points are in a plane parallel to the OCS base plane (UCS xyplane), else the result is unpredictable and depends on the CAD application used to open the DXF file  it may crash.

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 thePath
class.
start
(point: Vertex, tangent: Vertex) → 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: Vertex, tangent1: Vertex, tangent2: Vertex = 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: dict = None) → None¶ Render bezier curve as 2D/3D
Polyline
. Parameters
layout –
BaseLayout
objectforce3d – 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 aSpline
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, dxfattribs: dict = None)¶ Render curve as
Polyline
. Parameters
layout –
BaseLayout
objectlength – 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

render_spline
(layout: BaseLayout, length: float = 1, fit_points: int = 10, degree: int = 3, matrix: Matrix44 = None, dxfattribs: dict = None)¶ Render curve as
Spline
. Parameters
layout –
BaseLayout
objectlength – length measured along the spiral curve from its initial position
fit_points – count of spline fit points to use
degree – degree of Bspline
matrix – transformation matrix as
Matrix44
dxfattribs – DXF attributes for
Spline
 Returns

Random Paths¶
Random path generators for testing purpose.

ezdxf.render.
random_2d_path
(steps=100, max_step_size=1, max_heading=pi / 2, retarget=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=100, max_step_size=1, max_heading=pi / 2, max_pitch=pi / 8, retarget=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 zaxis in radians
max_pitch – limit pitch angle change per step to ± max_pitch/2, rotation about the xaxis in radians
retarget – specifies steps before changing global walking target