# bezierTangent 2
# https://processing.org/reference/bezierTangent_.html

noFill()
bezier(85, 20, 10, 10, 90, 90, 15, 80)
stroke(255, 102, 0)
steps <- 16
for (i in 0:steps) {
    t <- i/steps
    x <- bezierPoint(85, 10, 90, 15, t)
    y <- bezierPoint(20, 10, 90, 80, t)
    tx <- bezierTangent(85, 10, 90, 15, t)
    ty <- bezierTangent(20, 10, 90, 80, t)
    a <- atan2(ty, tx)
    a <- a - HALF_PI
    line(x, y, cos(a) * 8 + x, sin(a) * 8 + y)
}

# bezierTangent 1
# https://processing.org/reference/bezierTangent_.html

noFill()
bezier(85, 20, 10, 10, 90, 90, 15, 80)
steps <- 6
fill(255)
for (i in 0:steps) {
    t <- i/steps
    # Get the location of the point
    x <- bezierPoint(85, 10, 90, 15, t)
    y <- bezierPoint(20, 10, 90, 80, t)
    # Get the tangent points
    tx <- bezierTangent(85, 10, 90, 15, t)
    ty <- bezierTangent(20, 10, 90, 80, t)
    # Calculate an angle from the tangent points
    a <- atan2(ty, tx)
    a = a + PI
    stroke(255, 102, 0)
    line(x, y, cos(a) * 30 + x, sin(a) * 30 + y)
    # The following line of code makes a line inverse of the above
    # line line(x, y, cos(a)*-30 + x, sin(a)*-30 + y)
    stroke(0)
    ellipse(x, y, 5, 5)
}