raygeo.geo.algo.narrow

Functions

find_narrow_passages()

find_narrow_passages(
    polygon: Sequence[tuple[float, float]],
    holes: Sequence[Sequence[tuple[float, float]]] | None = None,
    max_width: float = 10,
) -> list[Sequence[tuple[float, float]]]

Detect narrow passages in a polygon.

A passage is narrow when it is narrower than max_width. The detection evaluates every boundary edge against every other boundary edge via an R-tree spatial index. Edges whose midpoints are within max_width of a non-adjacent edge (on a different polygon or a distinct part of the same polygon) produce a quadrilateral via convex hull of their four endpoints. All quadrilaterals are unioned and clipped to the pocket.

Raises: RuntimeError — If the polygon cannot be analyzed.

Parameter	Type	Description
polygon	Sequence[tuple[float, float]]	Outer boundary polygon.
holes	Sequence[Sequence[tuple[float, float]]] | None = None	List of hole (island) polygons.
max_width	float = 10	Passage-width threshold in mm.
Returns	list[Sequence[tuple[float, float]]]	List of polygons (each a list of (x, y) vertices).

Threshold sensitivity: narrow width barely registers; wider width qualifies more

Pocket with a central island: narrow passages (crimson) form in the necks around the island

Two triangular islands with a narrow gap; morphological opening creates narrow passage (crimson)