bezier.curved_polygon module

Curved polygon and associated helpers.

A curved polygon (in \(\mathbf{R}^2\)) is defined by the collection of Bézier curves that determine the boundary.

class bezier.curved_polygon.CurvedPolygon(*edges, **kwargs)

Bases: object

Represents an object defined by its curved boundary.

The boundary is a piecewise defined collection of Bézier curves.

Note

The direction of the nodes in each Curve on the boundary is important. When verifying, we check that one curve begins where the last one ended.

>>> import bezier
>>> nodes0 = np.asfortranarray([
...     [0.0,  0.0],
...     [1.0, -1.0],
...     [2.0,  0.0],
... ])
>>> edge0 = bezier.Curve(nodes0, degree=2)
>>> nodes1 = np.asfortranarray([
...     [2.0, 0.0],
...     [2.0, 1.0],
... ])
>>> edge1 = bezier.Curve(nodes1, degree=1)
>>> nodes2 = np.asfortranarray([
...     [2.0, 1.0],
...     [1.0, 2.0],
...     [0.0, 1.0],
... ])
>>> edge2 = bezier.Curve(nodes2, degree=2)
>>> nodes3 = np.asfortranarray([
...     [0.0, 1.0],
...     [0.0, 0.0],
... ])
>>> edge3 = bezier.Curve(nodes3, degree=1)
>>> curved_poly = bezier.CurvedPolygon(
...     edge0, edge1, edge2, edge3)
>>> curved_poly
<CurvedPolygon (num_sides=4)>

Though the endpoints of each pair of edges are verified to match, the curved polygon as a whole is not verified, so creating a curved polygon with self-intersections is possible:

>>> nodes0 = np.asfortranarray([
...     [0.0, 0.0],
...     [1.0, 0.0],
... ])
>>> edge0 = bezier.Curve(nodes0, degree=1)
>>> nodes1 = np.asfortranarray([
...     [1.0 , 0.0],
...     [1.25, 0.5],
...     [1.0 , 1.0],
... ])
>>> edge1 = bezier.Curve(nodes1, degree=2)
>>> nodes2 = np.asfortranarray([
...     [1.0, 1.0],
...     [2.0, 1.0],
... ])
>>> edge2 = bezier.Curve(nodes2, degree=1)
>>> nodes3 = np.asfortranarray([
...     [2.0, 1.0 ],
...     [1.0, 0.75],
...     [0.0, 0.0 ],
... ])
>>> edge3 = bezier.Curve(nodes3, degree=2)
>>> curved_poly = bezier.CurvedPolygon(
...     edge0, edge1, edge2, edge3)
>>> curved_poly
<CurvedPolygon (num_sides=4)>

Parameters:

• edges (Tuple [ Curve, ... ]) – The boundary edges of the curved polygon.
• kwargs – The only keyword argument accepted is _verify, which is a bool indicating if the edges should be verified as having shared endpoints. It defaults to True.

num_sides

int – The number of sides in the current polygon.

plot(pts_per_edge, color=None, ax=None)

Plot the current curved polygon.

Parameters:

• pts_per_edge (int) – Number of points to plot per curved edge.
• color (Optional [ Tuple [ float, float, float ] ]) – Color as RGB profile.
• ax (Optional [ matplotlib.artist.Artist ]) – matplotlib axis object to add plot to.

Returns:

The axis containing the plot. This may be a newly created axis.

Return type:

matplotlib.artist.Artist