Convert wkpool to a PSLG (planar straight line graph)

Usage

as_pslg(x, ...)

Arguments

x: A wkpool (will be passed through merge_coincident if not already)
...: passed to merge_coincident

Value

A list with P (vertex matrix) and S (segment matrix), the form used by RTriangle::pslg()

Details

Produces a planar straight line graph for constrained Delaunay triangulation. The vertex pool maps directly to P, and segment indices map directly to S (both 1-indexed). Shared boundaries appear once per feature.

A PSLG does not record which side of a segment is inside. For RTriangle, pass hole points from pool_holes() as H. The triangles come back as vertex and index matrices, and new_wkpool_tri() puts them on a vertex pool again; see vignette("triangulation", package = "wkpool").

For ear cutting that keeps the feature of each triangle, see pool_triangulate() (experimental).

Examples

x <- wk::as_wkb("POLYGON ((0 0, 1 0, 1 1, 0 1, 0 0))")
pool <- establish_topology(x)
as_pslg(pool)
#> $P
#>      [,1] [,2]
#> [1,]    0    0
#> [2,]    1    0
#> [3,]    1    1
#> [4,]    0    1
#> 
#> $S
#>      [,1] [,2]
#> [1,]    1    2
#> [2,]    2    3
#> [3,]    3    4
#> [4,]    4    1
#>