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An open Bezier curve

Source: R/curve_bezier.R
curve_bezier.Rd

curve_bezier is a drawable whose path follows a Bezier curve defined by an arbitrary number of control points (x, y), using the same Bernstein-polynomial machinery as shape_bezier(). Where shape_bezier() always closes back to its first control point (a consequence of every "polygon"-geometry drawable being rendered as a closed grid::polygonGrob()), curve_bezier() sets geometry = "path" and is rendered as an open grid::polylineGrob() instead, stopping at its last control point rather than looping back.

curve_beziers() is a vectorized version of curve_bezier(). Since x/y are themselves numeric vectors of control points for a single curve, curve_beziers() takes them as a list() of numeric vectors instead – one vector of control points per curve.

Usage

curve_bezier(x, y, n = 100L, trans = trans_identity(), ...)

curve_beziers(x, y, n = 100L, trans = trans_identity(), ...)

Arguments

x, y

For curve_bezier(), numeric vectors of control point coordinates, the same length, with at least two control points. For curve_beziers(), a list() of such vectors instead – one vector of control points per curve.

n

Number of points used to sample the curve. Default 100L.

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_beziers(), a sketch.

Details

style@fill has no effect for curve_bezier() – 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.

Every other argument may be a plain vector, recycled against x/y 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). The result is a sketch containing one curve_bezier() per list element/recycled row, rather than a single drawable.

See also

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

Examples

draw(curve_bezier(x = c(0, 0.5, 1), y = c(0, 1, 0)))


# unlike shape_bezier(), the curve stops at its last control point
# rather than closing back to the first
draw(curve_bezier(
  x = c(0, 0.25, 0.75, 1), y = c(0, 1, -1, 0), linewidth = 3
))


# a ribbon can be built around any curve_*() path with shape_strokepath()
draw(shape_strokepath(
  curve_bezier(x = c(0, 0.5, 1), y = c(0, 1, 0)),
  width = 0.15
))


draw(curve_beziers(
  x = list(c(0, 0.5, 1), c(2, 2.5, 3)),
  y = list(c(0, 1, 0), c(0, 1, 0))
))