shapes.arc#

shapes.arc(angle=None, radius=1.0, center=(0.0, 0.0, 0.0), div=None, eltype='line2', elsize=None, start=None, end=None, direction='ccw')#

Create a polygonal arc in a plane parallel to the xy-plane.

The arc lies in a plane parallel to the xy-plane and is defined relative to the given center. The arc is generated by sweeping either a given angular extent or between two absolute angles (start and end). The sweep direction can be explicitly controlled.

Two construction modes are supported:

1. angle mode: The arc starts at angle 0° (positive x-axis) and is swept by a given angle.

2. start/end mode: The arc is defined between two absolute angles (in degrees).

Parameters#

anglefloat, optional

Sweep angle in degrees starting from 0° along the positive x-axis. Use either angle OR (start, end), not both.

radiusfloat, optional

Radius of the arc. Must be > 0. Default is 1.0.

centerarray_like of shape (3,), optional

Coordinates of the arc center. Default is (0.0, 0.0, 0.0).

divint, optional

Number of subdivisions (segments) along the arc. Must be >= 1. Default is 10.

elsizefloat, optional

Target element size along the arc (mutually exclusive with div).

eltype{“line2”, “tri3”}, optional

Element type of the returned mesh:

  • “line2”: returns only the arc contour as 2-node line elements.

  • “tri3”: returns a filled arc sector as 3-node triangular elements, formed by connecting the arc to the center.

startfloat, optional

Starting angle in degrees (used with end). Normalized to [0, 360).

endfloat, optional

Ending angle in degrees (used with start). Normalized to [0, 360).

direction{“ccw”, “cw”}, optional

Sweep direction: - “ccw”: counterclockwise (positive angular sweep) - “cw”: clockwise (negative angular sweep)

Returns#

Mesh

A mesh representing either the arc contour or a filled arc sector.

Examples#

Arc defined by sweep angle:

>>> A1 = arc(angle=180, radius=1.0, div=4)
>>> print(A1.coords)
[[ 1.      0.      0.    ]
 [ 0.7071  0.7071  0.    ]
 [ 0.      1.      0.    ]
 [-0.7071  0.7071  0.    ]
 [-1.      0.      0.    ]]

Arc defined by start/end angles:

>>> A2 = arc(start=0, end=90, radius=1.0, div=4, direction="ccw")
>>> print(A2.coords)
[[1.     0.     0.    ]
 [0.9239 0.3827 0.    ]
 [0.7071 0.7071 0.    ]
 [0.3827 0.9239 0.    ]
 [0.     1.     0.    ]]

Clockwise arc:

>>> A3 = arc(start=90, end=0, radius=1.0, div=4, direction="cw")
>>> print(A3.coords)
[[0.     1.     0.    ]
 [0.3827 0.9239 0.    ]
 [0.7071 0.7071 0.    ]
 [0.9239 0.3827 0.    ]
 [1.     0.     0.    ]]

Filled sector:

>>> A4 = arc(angle=180, radius=1.0, div=3, eltype="tri3")
>>> print(A4)
Mesh: n_nodes: 5, n_elems: 3, plexitude: 3, level: 2, eltype: tri3
  BBox: [-1.  0.  0.], [1.    0.866 0.   ]
  Size: [2.    0.866 0.   ]
  Length: 5.0  Area: 1.299

Using element size instead of number of divisions:

>>> A3 = arc(angle=90, radius=1.0, elsize=0.2)
>>> print(A3.lengths())
[0.196 0.196 0.196 0.196 0.196 0.196 0.196 0.196]
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