Delaunay triangulation

Returns one multipolygon per input geometry, whose parts are that geometry's triangles. The output has the same length as the input.

Usage

ga_triangulate_delaunay(x, constrained = TRUE, snap_radius = 1e-04)

Arguments

x

a GeoArrow geometry array

constrained

whether to constrain the triangulation to the input's edges. TRUE by default

snap_radius

coordinates closer together than this are snapped to the same position; length 1 or the same length as x. geo uses 1e-4 by default

Value

a GeoArrow multipolygon array of the same length as x

Details

A constrained triangulation keeps the input's edges and returns only the triangles that fall inside the geometry. An unconstrained triangulation triangulates the convex hull of the input's vertices, ignoring its edges, so it may cross holes and concavities.

A null geometry, or one that cannot be triangulated, becomes a null element.

References

TriangulateDelaunay

See also

Other triangulate: ga_triangulate_earcut()

Examples

fp <- system.file("shape/nc.shp", package = "sf")
nc <- as.data.frame(read_shapefile(fp))

# constrained keeps the triangles inside the county boundary
tri <- ga_triangulate_delaunay(nc$geometry)
tri$length
#> [1] 100

# unconstrained fills the convex hull instead, so it covers more
hull <- ga_triangulate_delaunay(nc$geometry, constrained = FALSE)
head(as.vector(ga_unsigned_area(tri)), 3)
#> [1] 0.11428350 0.06139976 0.14301628
head(as.vector(ga_unsigned_area(hull)), 3)
#> [1] 0.12484563 0.07437819 0.15586877