Tutorial Request: drawing multi sided polygons w/ Bezier Curves

micahmicah

Hello!

I'm still a bit new to programmatic drawing and I was curious about writing scripts to make multi-sided polygons such as triangles, hexagons, etc. using the BezierPath() method.

My math skills are rather rusty at this point so I'd love some pointers.

Thanks!

gferreira

hello @micahmicah,

regular polygons can be described using vectors.

a vector has a length and an angle.

in regular polygons:

all sides have the same length
the sum of all external angles is 360°

here is a simple example in code:

# define polygon parameters
x, y = 300, 200
sides = 5
perimeter = 1640
angleStart = 0
angleTotal = 360
autoclose = True

# calculate side length & angle
side = perimeter / sides
angleStep = abs(angleTotal / sides)

# convert angles to radians!
angleStep = radians(angleStep)
angleStart = radians(angleStart)

# create the polygon shape
B = BezierPath()

angle = angleStart
for i in range(sides):
    # this is the crucial part:
    # use trigonometry to calculate point B
    # from point A, angle, and distance
    x += cos(angle) * side
    y += sin(angle) * side

    if i == 0:
        B.moveTo((x, y))
    else:
        B.lineTo((x, y))

    angle += angleStep

if autoclose:
    B.closePath()

fill(0, 1, 1)
strokeWidth(30)
lineCap('round')
lineJoin('round')
stroke(1, 0, 1)
drawPath(B)

gferreira

bonus: Turtle

from turtle import *

x, y = 300, 200
sides = 7
side = 100
angleTotal = 360

angleStep = abs(angleTotal / sides)

Screen()
t = Turtle()

for i in range(sides):
    t.forward(side)
    t.left(angleStep)

done()

↳ run this script in Terminal or SublimeText

micahmicah

Thank you so much!