Polygon rings

A polygon consists of 1 or more rings. The first ring denotes the outer boundary of the polygon whereas any additional rings marks holes within that boundary. If the outer boundary is empty (i.e. doesn't consist of any vertices) the polygon is said to be unbounded. The different rings can be extracted, modified, or, in the case of holes, added or removed. A special function, connect_holes() exist to remove holes by connecting them with the outer boundary, by tracing upwards from the top vertex in the hole until the boundary is reached. Connecting holes will make any polygon invalid as the part connecting the hole with the boundary will consist of two overlapping edges.

Usage

n_holes(x)

is_unbounded(x)

boundary(x)

boundary(x) <- value

hole(x, which)

hole(x, which = NULL) <- value

n_rings(x)

rings(x)

connect_holes(x)

Arguments

x, value

polyclid_polygon vector

which

integer vector recycled to the length of x referencing the hole to get or set

Value

A new polyclid_polygon vector or, in the case of n_holes() an integer vector

Examples

poly <- polygon(
  c(0, 10, 10, 0, 1, 5, 1),
  c(0, 0, 10, 10, 1, 1, 5),
  hole_id = c(1, 1, 1, 1, 2, 2, 2)
)
plot(poly, col = "grey")


n_holes(poly)
#> [1] 1

plot(boundary(poly), col = "grey")

plot(hole(poly, 1), col = "grey")


# Change the boundary
boundary(poly) <- circle(point(5, 5), 40)
plot(poly, col = "grey")


# Add a hole
hole(poly) <- circle(point(7, 7), 9)
plot(poly, col = "grey")


# Change a hole (by using a combination of hole and def setters)
def(hole(poly, 1), "x") <- def(hole(poly, 1), "x") + 2
plot(poly, col = "grey")


# Or remove it
hole(poly, 1) <- NULL
plot(poly, col = "grey")


# Holes can also be removed by connecting them to the boundary
poly <- connect_holes(poly)
plot(poly, col = "grey", force_valid = FALSE)