Spline 样条

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.
SPLINE 实体（DXF 参考）是一个 3D 曲线，所有坐标即使是 2D 平面曲线也必须是 3D 坐标。

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.
样条曲线由控制点、节点值和权重定义。控制点建立样条，不同类型的节点矢量决定曲线的形状，而有理样条的权重则定义了一个控制点对形状影响的强度。

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.
可以仅从拟合点创建样条曲线 - 节点值和权重是可选的（已在 AutoCAD 2010 中测试）。如果你添加额外的数据，请确保你知道你在做什么，因为无效的数据可能会使整个 DXF 文件无效。

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.
函数 ezdxf.math.fit_points_to_cad_cv() 从给定的拟合点计算控制顶点。 这些控制顶点定义了一个三次 B 样条，它在视觉上与 BricsCAD 和 AutoCAD 从拟合点创建的 SPLINE 实体相匹配。

See also 另请参见

• Wikipedia article about B_splines
  Wikipedia 关于 B_splines 的文章

• Department of Computer Science and Technology at the Cambridge University
  剑桥大学计算机科学与技术系

• Tutorial for Spline 样条教程

Subclass of 子类	ezdxf.entities.DXFGraphic
DXF type DXF 类型	'SPLINE'
Factory function 工厂函数	see table below 请参见下面的表格
Inherited DXF attributes 继承的 DXF 属性	Common graphical DXF attributes 常见的图形 DXF 属性
Required DXF version 所需 DXF 版本	DXF R2000 ('AC1015')

Factory Functions
工厂函数

Basic spline entity 基本样条实体	add_spline()
Spline control frame from fit points 从拟合点的样条控制框架	add_spline_control_frame()
Open uniform spline 开放均匀样条	add_open_spline()
Closed uniform spline 封闭均匀样条	add_closed_spline()
Open rational uniform spline 开放有理均匀样条	add_rational_spline()
Closed rational uniform spline 封闭有理均匀样条	add_closed_rational_spline()

class ezdxf.entities.Spline

All points in WCS as (x, y, z) tuples
所有点在 WCS 中作为(x, y, z)三元组

dxf.degree
度

Degree of the spline curve (int).
样条曲线的度数（整数）。

dxf.flags
dxf.标志

Bit coded option flags, constants defined in ezdxf.lldxf.const:
位编码选项标志，常量定义在ezdxf.lldxf.const:

dxf.flags	Value 价值	Description 描述
CLOSED_SPLINE	1	Spline is closed 样条已关闭
PERIODIC_SPLINE	2
RATIONAL_SPLINE	4
PLANAR_SPLINE	8
LINEAR_SPLINE	16	planar bit is also set 平面位也被设置

dxf.n_knots

Count of knot values (int), automatically set by ezdxf (read only)
结点值计数（int），由ezdxf自动设置（只读）

dxf.n_fit_points

Count of fit points (int), automatically set by ezdxf (read only)
拟合点数（整数），由 ezdxf 自动设置（只读）

dxf.n_control_points
dxf.n_control_points

Count of control points (int), automatically set by ezdxf (read only)
控制点的数量（整数），由 ezdxf 自动设置（只读）

dxf.knot_tolerance
dxf.knot_tolerance¶

Knot tolerance (float); default is 1e-10
结容差（浮点数）；默认值为 1e-10

dxf.fit_tolerance

Fit tolerance (float); default is 1e-10
配合公差（浮动）；默认值为 1e-10

dxf.control_point_tolerance
dxf.control_point_tolerance

Control point tolerance (float); default is 1e-10
控制点公差（浮点数）；默认值为 1e-10

dxf.start_tangent
dxf.start_tangent

Start tangent vector as 3D vector in WCS
在WCS中将起始切线向量作为 3D 向量

dxf.end_tangent

End tangent vector as 3D vector in WCS
在 WCS 中将终点切向量表示为 3D 向量

closed
关闭

True if spline is closed. A closed spline has a connection from the last control point to the first control point. (read/write)
如果样条曲线是闭合的，则为True。闭合样条曲线从最后一个控制点连接到第一个控制点。（读/写）

control_points

VertexArray of control points in WCS.
在VertexArray中作为控制点的WCS。

fit_points

VertexArray of fit points in WCS.
在 WCS 中的拟合点的 VertexArray。

knots
结节

Knot values as array.array('d').
Knot 值为array.array('d')。

weights
权重

Control point weights as array.array('d').
控制点权重为array.array('d')。

control_point_count() → int

Count of control points. 控制点数量。

fit_point_count() → int

Count of fit points. 适配点的数量。

knot_count() → int

Count of knot values. 结点值的数量。

construction_tool() → BSpline

Returns the construction tool ezdxf.math.BSpline.
返回构造工具ezdxf.math.BSpline。

apply_construction_tool(s) → Spline

Apply SPLINE data from a BSpline construction tool or from a geomdl.BSpline.Curve object.
应用来自BSpline构建工具或来自geomdl.BSpline.Curve对象的 SPLINE 数据。

flattening(distance: float, segments: int = 4) → Iterator[Vec3]
展平距离: float, 分段: int = 4→ Iterator[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.
自适应递归展平。参数分段是两个节点之间近似分段的最小数量，如果从近似分段的中心到曲线的距离大于距离，则分段将被细分。

Parameters 参数:

• distance – maximum distance from the projected curve point onto the segment chord.
  distance – 投影曲线点到线段弦的最大距离。

• segments – minimum segment count between two knots
  segments – 两个节点之间的最小段数

set_open_uniform(control_points: Sequence[UVec], degree: int = 3) → None

Open B-spline with a uniform knot vector, start and end at your first and last control points.
带有均匀节点矢量的开放 B 样条，起点和终点为您的第一个和最后一个控制点。

set_uniform(control_points: Sequence[UVec], degree: int = 3) → None

B-spline with a uniform knot vector, does NOT start and end at your first and last control points.
具有均匀节点向量的 B 样条，并不从第一个和最后一个控制点开始和结束。

set_closed(control_points: Sequence[UVec], degree=3) → None

Closed B-spline with a uniform knot vector, start and end at your first control point.
使用均匀节点向量的封闭 B 样条，从第一个控制点开始和结束。

set_open_rational(control_points: Sequence[UVec], 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.
带有均匀节点向量的开放有理 B 样条，在第一个和最后一个控制点处开始和结束，并通过加权每个控制点具有额外的控制可能性。

set_uniform_rational(control_points: Sequence[UVec], 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.
带有均匀节点向量的有理 B 样条不会在第一个和最后一个控制点开始和结束，并且通过对每个控制点赋予权重具有额外的控制可能性。

set_closed_rational(control_points: Sequence[UVec], 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.
闭合有理 B 样条具有均匀的节点向量，从第一个控制点开始和结束，并通过对每个控制点加权提供额外的控制可能性。

transform(m: Matrix44) → Spline

Transform the SPLINE entity by transformation matrix m inplace.
通过转换矩阵m原地转换 SPLINE 实体。

classmethod from_arc(entity: DXFGraphic) → Spline

Create a new SPLINE entity from a CIRCLE, ARC or ELLIPSE entity.
从圆、弧或椭圆实体创建一个新的样条实体。

The new SPLINE entity has no owner, no handle, is not stored in the entity database nor assigned to any layout!
新的 SPLINE 实体没有所有者，没有句柄，未存储在实体数据库中，也未分配给任何布局！