Changing Squares to Five Point Stars with JVR Code

FutureDays

Hi All,

Having a ball learning drawbot so thanks to everyone who has been involved in the development process to date. Recently I been playing around with the source code for one of Just Van Rossum's StackoSquares animations. That said, I have a question, in order to change the object from multiple squares to multiple five point stars, is the solution simply changing the square object to a star object. If so how would I write the star object code. Very new to coding so any help would be gratefully appreciated.

Best.

Robert

PS: The code is below this line of type.

CANVAS = 500
SQUARESIZE = 158
NSQUARES = 50
SQUAREDIST = 6

width = NSQUARES * SQUAREDIST

NFRAMES = 50

for frame in range(NFRAMES):
    newPage(CANVAS, CANVAS)
    frameDuration(1/20)
    
    fill(0)
    rect(0, 0, CANVAS, CANVAS)

    phase = 2 * pi * frame / NFRAMES  # angle in radians
    startAngle = 90 * sin(phase)
    endAngle = 90 * sin(phase + 0.5 * pi)

    translate(CANVAS/2 - width / 2, CANVAS/2)

    fill(1)
    stroke(0)

    for i in range(NSQUARES + 1):
        f = i / NSQUARES
        save()
        translate(i * SQUAREDIST, 0)
        scale(0.7, 1)
        rotate(startAngle + f * (endAngle - startAngle))
        rect(-SQUARESIZE/2, -SQUARESIZE/2, SQUARESIZE, SQUARESIZE)
        restore()

saveImage("StackOfSquares.gif")

gferreira

hi. see this tweet by Just himself

FutureDays

@gferreira
Hi. That is exactly what I was hoping to achieve. Hopefully I can make this work.

Best.

Robert

FutureDays

@FutureDays

Hi All,

I am now totally stuck:

CANVAS = 1440

NFRAMES = 1

for frame in range(NFRAMES):
    newPage(CANVAS, CANVAS)
    frameDuration(1/20)
    
fill(0)
rect(0, 0, CANVAS, CANVAS)

phase = 2 * pi * frame / NFRAMES 
startAngle = 90 * sin(phase)
endAngle = 90 * sin(phase + 0.5 * pi)


translate(CANVAS/2, CANVAS/2)

fill(1)
stroke(0)

for i in range(20):
    save()
    translate(i * 10)
    scale(1.1)
    rotate(380)
    def star(x, y, n, r1, r2):
        pts = []
        for i in range(n * 2):
            a = i * pi / n
            r = r2 if i % 2 else r1
            pts.append((x + r * sin(a), y + r * cos(a)))
        polygon(*pts)
    star(1, -95, 5, 450, 260)
    restore()

saveImage("StarTest.gif")

Any help would be very much appreciated

Best,

Robert

gferreira

hi Robert,

very little needs to change in your previous script to replace the rectangles with stars:

add the star function at the top of your script, so you can use it later on
where the rect function is called, use star instead

# copied from http://twitter.com/justvanrossum/status/1098138752805941248
def star(x, y, n, r1, r2):
    pts = []
    for i in range(n * 2):
        a = i * pi / n
        r = r2 if i % 2 else r1
        pts.append((x + r * sin(a), y + r * cos(a)))
    polygon(*pts)

# ---------------
# original script
# ---------------

CANVAS = 500
SQUARESIZE = 158
NSQUARES = 50
SQUAREDIST = 6

width = NSQUARES * SQUAREDIST

NFRAMES = 50

for frame in range(NFRAMES):
    newPage(CANVAS, CANVAS)
    frameDuration(1/20)
    
    fill(0)
    rect(0, 0, CANVAS, CANVAS)

    phase = 2 * pi * frame / NFRAMES  # angle in radians
    startAngle = 90 * sin(phase)
    endAngle = 90 * sin(phase + 0.5 * pi)

    translate(CANVAS/2 - width / 2, CANVAS/2)

    fill(1)
    stroke(0)

    for i in range(NSQUARES + 1):
        f = i / NSQUARES
        save()
        translate(i * SQUAREDIST, 0)
        scale(0.7, 1)
        rotate(startAngle + f * (endAngle - startAngle))

        # replace rect with star
        # rect(-SQUARESIZE/2, -SQUARESIZE/2, SQUARESIZE, SQUARESIZE)
        star(0, 0, 5, SQUARESIZE, SQUARESIZE * 0.5)

        restore()

saveImage("StackOfSquares.gif")

there’s one little catch: to draw the rectangles from center, we had to shift the origin point by half the square size (-SQUARESIZE/2). this is not necessary when drawing the star, because it is already drawn from center – so we simply draw it at (0, 0).

hope it makes sense! cheers

FutureDays

@gferreira

Hello gferreira,

Thank you so much the reply has been very helpful. I can see that I was thinking too much about modifying all areas of the code instead of changing a small component.

Enjoy the day.

Best.

Robert