R/fractal-billow.R

In ambient: A Generator of Multidimensional Noise

#' Billow (cloud-like, lumpy) fractal
#'
#' The billow fractal is a slight modification of the [fbm()] fractal. Before
#' adding the new layer onto the last, the new layer is modified by taking the
#' absolute value, multiplying by 2, and subtracting one. The result is that the
#' new value will not contain negative values and so will always add on top of
#' the old values. This function is intended to be used in conjunction with
#' [fracture()]
#'
#' @inheritParams fbm
#'
#' @family Fractal functions
#'
#' @export
#'
#' @examples
#' grid <- long_grid(seq(1, 10, length.out = 1000), seq(1, 10, length.out = 1000))
#'
#' grid$simplex <- fracture(gen_simplex, billow, octaves = 8, x = grid$x,
#'                          y = grid$y)
#' plot(grid, simplex)
#'
billow <- function(base, new, strength, ...) {
  base + (2 * abs(new) - 1) * strength
}
attr(billow, 'finalise') <- function(x) x + 0.5