Default refinement edge-length floor

min_edge_frac times the median constraint segment length, which keeps the refiner from cascading into sharp input corners, capped at area_edge_frac * sqrt(max_area) so the floor never blocks the area target (a triangle of area A has edges of order sqrt(A)). With no segments only the area cap applies; with neither, 0.

Usage

default_min_edge_length(
  x,
  y,
  s0,
  s1,
  max_area = NULL,
  min_edge_frac = 0.3,
  area_edge_frac = 0.25
)

Arguments

x, y

vertex coordinates

s0, s1

1-based vertex indices of constraint segment start/end (may be NULL)

max_area

maximum triangle area (Ruppert refinement by area), NULL for none

min_edge_frac

fraction of the median constraint segment length used when min_edge_length is NULL

area_edge_frac

fraction of sqrt(max_area) that caps the default floor

Value

a single non-negative number, the edge-length floor that cdt_triangulate() uses when min_edge_length = NULL

Examples

x <- c(0, 1, 1, 0)
y <- c(0, 0, 1, 1)
s0 <- 1:4
s1 <- c(2:4, 1)
## 0.3 times the median segment length
default_min_edge_length(x, y, s0, s1)
#> [1] 0.3
## a small area target caps the floor at 0.25 * sqrt(max_area)
default_min_edge_length(x, y, s0, s1, max_area = 0.01)
#> [1] 0.025
## no segments and no area target: no floor
default_min_edge_length(x, y, integer(0), integer(0))
#> [1] 0