translation along a path

find-bezier-point-2.py

'''draw a range of shapes along a bezier segment'''

# converted from:
# http://13thparallel.com/archive/bezier-curves/

def B1(t): return t*t*t
def B2(t): return 3*t*t*(1-t)
def B3(t): return 3*t*(1-t)*(1-t)
def B4(t): return (1-t)*(1-t)*(1-t)

def getPoint(t, p1, p2, p3, p4):
    x1, y1 = p1
    x2, y2 = p2
    x3, y3 = p3
    x4, y4 = p4
    x = x1*B1(t) + x2*B2(t) + x3*B3(t) + x4*B4(t)
    y = y1*B1(t) + y2*B2(t) + y3*B3(t) + y4*B4(t)
    return x, y

size(200, 200)
fill(None)
stroke(1, 0, 0)
strokeWidth(1)

B = BezierPath()
B.moveTo((60, 26))
B.curveTo((-34, 186), (210, 222), (158, 38))
drawPath(B)

p1, p4 = B.onCurvePoints
p2, p3 = B.offCurvePoints

Variable([
    dict(name='n', ui='Slider', args=dict(value=80, minValue=2, maxValue=160)),
    dict(name='a', ui='Slider', args=dict(value=45.0, minValue=0.0, maxValue=180.0)),
    dict(name='f', ui='Slider', args=dict(value=0.5, minValue=0.01, maxValue=1.0)),
],
globals())

n = int(n)
r = 10

for i in range(n+1):
    t = i * (1.0 / n)
    x, y = getPoint(t, p1, p2, p3, p4)
    save()
    translate(x, y)
    rotate(a)
    oval(-r, -r*f, r*2, r*f*2) 
    restore()