A wandering scribble curve

curve_scribble is a drawable whose path is a single random wandering line – a random finite sum of sine harmonics – built from the same internal scribble_lines() generator that fill_scribble() uses to texture a tile's interior, but scaled here into an arbitrary bounding box on the sketch's own coordinate plane rather than tiled inside a fill pattern. Where fill_scribble() scatters several such lines across a repeating tile as a texture, curve_scribble() draws exactly one as a standalone open curve.

curve_scribbles() is a vectorized version of curve_scribble(): each argument may be a vector, recycled against the others via purrr::pmap()'s own vctrs-based rules (any length-1 element is broadcast to the common length; mismatched lengths greater than 1 raise an error).

Usage

curve_scribble(
  x = 0,
  y = 0,
  width = 1,
  height = 1,
  direction = "horizontal",
  n_harmonics = 3L,
  amplitude = 0.35,
  n = 200L,
  seed = 1L,
  trans = trans_identity(),
  ...
)

curve_scribbles(
  x = 0,
  y = 0,
  width = 1,
  height = 1,
  direction = "horizontal",
  n_harmonics = 3L,
  amplitude = 0.35,
  n = 200L,
  seed = 1L,
  trans = trans_identity(),
  ...
)

Arguments

x, y

Coordinates of the curve's origin. Default 0.

width, height

Extent of the curve's bounding box along/across its direction of travel. Must be positive. Default 1.

direction

Either "horizontal" (the curve runs left-right) or "vertical" (top-bottom). Default "horizontal".

n_harmonics

Number of sine harmonics summed to build the curve. Must be a positive integer. Default 3L.

amplitude

Maximum total wiggle amplitude, as a fraction of height (for direction = "horizontal") or width (for "vertical"), split across n_harmonics. Must be a non-negative number. Default 0.35.

n

Number of points sampled along the curve. Must be a positive integer of at least 2L. Default 200L.

seed

Integer seed for the random harmonics. Default 1L.

trans

A trans object applied to the curve's computed points. Default trans_identity() (no transform).

...

Arguments passed to style().

Value

A drawable.

For curve_scribbles(), a sketch.

Details

The underlying line is generated in (along, across) form, along running from 0 to 1 and across wandering around a random baseline near 0.5 (see scribble_lines()'s own details for why this particular construction was chosen – periodicity, needed for tiling, is irrelevant here). x/y place the curve's origin, and width/ height scale it: for direction = "horizontal" (the default), along maps to x + along * width and across to y + across * height, so the curve runs left-to-right; for direction = "vertical", the mapping swaps (along maps to y, across to x), so the curve runs bottom-to-top instead.

style@fill has no effect for curve_scribble() – see drawable's geometry documentation for why "path" geometries have no interior to fill. Passing fill via ... is still accepted (it's simply ignored at draw time), since style() is shared across every geometry.

Varying seed per curve is usually what makes several scribbles look distinct from each other. The result is a sketch containing one curve_scribble() per recycled row, rather than a single drawable.

See also

Other 1D curves: curve_arc(), curve_bezier(), curve_line(), curve_raw(), curve_spiral(), curve_twist()

Examples

draw(curve_scribble(width = 2, height = 0.5, seed = 5591))


# more harmonics and higher amplitude give a more agitated wiggle
draw(curve_scribble(
  width = 2, height = 0.5, n_harmonics = 8, amplitude = 0.6, seed = 5591
))


# direction = "vertical" runs the curve bottom-to-top instead
draw(curve_scribble(
  width = 0.5, height = 2, direction = "vertical", seed = 5591
))


draw(curve_scribbles(x = 1:3, width = 0.8, height = 0.5, seed = 1:3))


# stacked scribbles, like several strands of hatching
draw(curve_scribbles(y = 1:6, width = 3, height = 0.6, seed = 1:6))