How to close a "noisy" circular shape?

solub

Hi everyone !

When trying to draw a noisy circle I'm facing the following problem: the last vertex and the first vertex don't share the same position (due to the applied noise) so "closing" the circle becomes impossible:

How can I fix this ?

def setup():
    size(600, 600)

def draw():
    background(255)

    n_points = 300
    angle = radians(360) / n_points
    radius = 300

    beginShape()
    strokeWeight(4)
    for e in range(n_points):
        n = noise(map(e, 0, n_points, 0, 3))
        x = cos(angle * e) * radius * n
        y = sin(angle * e) * radius * n
        vertex(width / 2 + x, height / 2 + y)
    endShape(CLOSE)

solub

Ok, so this snippet below do the trick BUT I still don't really get what I'm doing.

    def setup():
        size(600, 600)

    def draw():
        background(255)

        n_points = 300
        angle = radians(360) / n_points
        radius = 300
        t = .8

        beginShape()
        strokeWeight(4)
        for e in range(n_points):
            x = cos(angle * e) * radius
            y = sin(angle * e) * radius 
            p = PVector(x, y).normalize()
            n = map(noise(p.x + t, p.y + t), 0, 1, 70, 120)
            p.mult(n*2)
            vertex(width / 2 + p.x, height / 2 + p.y)
        endShape(CLOSE)

(Click here to see the motion generated by the noise)

I've recently purchased the amazing "Generative Design" book by Benedikt Gross and found that he doesn't map the noise like I did in this snippet but rather apply noise to "map" (see first post).

In short, he writes something like:

noise(map(value,0,range,0,noiseRange)) * someValue

instead of:

map(noise(x, y), 0, 1, min, max)

Can someone please explain me the difference here ? And why this difference prevented me to close the first circle ?

Thank you.

jeremydouglass

I think the thing to focus on is how you get Perlin noise to give you repeating values. That's what you want -- a wobbly line that begins at the same height it ends, so that when wrapped in a circle there is no gap.

The basic answer to this question is that it is the ratio of period to octaves that gives you a repeating pattern. In 2D, it creates a "tile" that seemlessly matches its neighbors; in 1D it creates a wrapping line (or a circular outline).

Here is an in-depth discussion of how noise settings affect the way that Perlin noise repeats:

• https://gamedev.stackexchange.com/a/23705/95377

---

Regarding your specific code question:

Your use of map in map(noise(x, y), 0, 1, min, max) seems like it might be the equivalent to Gross's use of someValue -- it is for scaling the output:

`noise(mappedValue) * someValue

His use of map inside noise looks different from yours... notice that map only returns one value, so Gross is only passing noise() a single argument to produce 1D noise.

• https://processing.org/reference/noise_.html

solub

Thanks a bunch Jeremy, you're the best.