Generate a tube (generalized cylinder) along a path

Sweeps a circular cross-section along the points of path, which allows for curved shapes such as arcs, Bezier samples of network edges or streamlines. A path of exactly two points produces the same mesh as generate_cylinder().

Usage

generate_tube(
  path,
  radius = 0.1,
  segments = 12L,
  color = c(1, 1, 1, 1),
  cap_start = TRUE,
  cap_end = TRUE
)

Arguments

path: Nx3 numeric matrix of path points (or a length-3 vector).
radius: Tube radius (default 0.1).
segments: Subdivision count around the circumference (default 12).
color: Length-4 RGBA colour.
cap_start: Whether to close the beginning of the tube (default TRUE).
cap_end: Whether to close the end of the tube (default TRUE).

Value

A mesh descriptor list.

Details

The cross-section frames are computed by parallel transport (rotation-minimizing frames), so the tube does not twist around its own axis. Consecutive duplicate points are removed; a path with fewer than two distinct points yields an empty mesh.

Examples

path <- matrix(c(0, 0, 0, 1, 1, 0, 2, 0, 0), ncol = 3, byrow = TRUE)
arc <- generate_tube(path, radius = 0.1, segments = 12,
                     cap_start = FALSE, cap_end = FALSE)
nrow(arc$vertices) > 0
#> [1] TRUE