Triangulate with per-vertex attributes carried onto new vertices

cdt_triangulate() plus a PA matrix of per-input-vertex attributes (z, m, t ...), returned as $PA aligned with the output vertices. Input vertices keep their values; Steiner vertices get values interpolated from the unrefined constrained triangulation of the input.

Usage

cdt_triangulate_attr(x, y, s0 = NULL, s1 = NULL, PA = NULL, ...)

Arguments

x, y: vertex coordinates
s0, s1: 1-based vertex indices of constraint segment start/end (may be NULL)
PA: numeric matrix with one row per input vertex (or NULL)
...: passed to cdt_triangulate()

Value

the list returned by cdt_triangulate(), plus PA, a matrix with one row per output vertex and the columns of the input PA (absent when PA = NULL)

Examples

x <- c(0, 1, 1, 0)
y <- c(0, 0, 1, 1)
## a sloping surface: z rises with x
r <- cdt_triangulate_attr(x, y, 1:4, c(2:4, 1),
                          PA = cbind(z = 10 * x), max_area = 0.02)
## Steiner vertices carry interpolated z
head(cbind(r$P, r$PA)[r$origin == "steiner", , drop = FALSE])
#>                   z
#> [1,] 0.50 0.50  5.0
#> [2,] 0.50 0.00  5.0
#> [3,] 0.00 0.50  0.0
#> [4,] 0.25 0.25  2.5
#> [5,] 0.50 1.00  5.0
#> [6,] 1.00 0.50 10.0
all.equal(r$PA[, "z"], 10 * r$P[, 1])
#> [1] TRUE