Delaunay triangulation

Returns one multipolygon per input geometry, whose parts are that geometry's triangles. ga_triangulate_delaunay() preserves the input's length.

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

the distance below which to snap coordinates 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

With constrained = TRUE, ga_triangulate_delaunay() keeps the input's edges and returns only the triangles that fall inside the geometry. With constrained = FALSE, it triangulates the convex hull of the input's vertices, ignoring the edges, so the triangles may cross holes and concavities.

It returns a null element for a null geometry or one it cannot triangulate.

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))

# with constrained = TRUE you get only triangles inside the county boundary
tri <- ga_triangulate_delaunay(nc$geometry)
tri$length
#> [1] 100

# set constrained = FALSE to fill the convex hull instead, which 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