GitHub

Orientation

Many geometric processing algorithms for 2D geometries rely on the concept of orientation, which is illustrated below.

Meshes.orientation — Function
orientation(geom)

Returns the orientation of the geometry geom as either counter-clockwise (CCW) or clockwise (CW).

source

For polygons without holes, the function returns the orientation of the boundary, which is a Ring:

tri = Triangle((0, 0), (1, 0), (0, 1))

orientation(tri)
CCW::OrientationType = 1
tri = Triangle((0, 0), (0, 1), (1, 0))

orientation(tri)
CW::OrientationType = 0

For polygons with holes, the function returns a vector with the orientation of all constituent rings:

outer = [(0, 0), (1, 0), (1, 1), (0, 1)]
hole1 = [(0.2, 0.2), (0.2, 0.4), (0.4, 0.4), (0.4, 0.2)]
hole2 = [(0.6, 0.2), (0.6, 0.4), (0.8, 0.4), (0.8, 0.2)]
poly  = PolyArea([outer, hole1, hole2])

orientation(poly)
3-element Vector{OrientationType}:
 CCW::OrientationType = 1
 CW::OrientationType = 0
 CW::OrientationType = 0