Speed profiles for hand-drawn strokes

Usage

speed_flat(value = 1)

speed_human(
  value = 1,
  taper = 0.65,
  start = 0.55,
  end = 0.65,
  peak = 1.4,
  peak_at = 0.45,
  turn_slowdown = 0.45,
  min = 0.05
)

Arguments

value: Base speed multiplier. 1 preserves the default distance-based timing heuristic, values greater than 1 draw faster, and values below 1 draw slower.
taper: How strongly speed changes over the stroke. 0 keeps the speed flat; 1 applies the full profile shape.
start, end: Relative speed at the start and end of a human-style stroke when taper = 1.
peak: Relative peak speed reached during the stroke when taper = 1.
peak_at: Position of peak speed along the stroke, in the range 0 to 1.
turn_slowdown: How strongly speed is reduced at sharp turns.
min: Minimum speed multiplier returned by the profile.

Value

A speed-profile function for the speed argument of hand() and human_hand(). Custom functions can also be supplied directly; they must accept t, normalized stroke progress in the range 0 to 1, turn in the range 0 to 1, and length, the total stroke length in device units. Speed profiles return positive speed multipliers. Custom functions must be vectorized over t and turn, and return either length 1 or length(t).

Examples

plot.new()
plot.window(c(0, 10), c(0, 10))
draw_rough_lines(c(1, 9), c(8, 8), lwd = 5,
                 hand = hand(speed = speed_flat(0.5)))
draw_rough_lines(c(1, 9), c(5, 5), lwd = 5,
                 hand = hand(speed = speed_human()))