## Description of this creative coding animation that I can't understand.

It's a creative coding animation written in Processing programming language.

When I was playing around with Vector Field written by GenerateMe.

Drawing vector field | GenerateMe
https://generateme.wordpress.com/2016/04/24/drawing-vector-field/

I found some formula that makes a square shape.
Interesting but I can't understand why (as always).

I don't know why, but I can use it. And I made an animation to draw many different square shapes.

## Processing example code.

This code does not display any images on screen but generates image files in frames directory.
You can make an animation with these files.

Please feel free to use this example code.
To see other works based on my code is my pleasure. And my honor.

```/**
* Piece in the Shape of a Square.
*
* @author @deconbatch
* @version 0.1
* Processing 3.2.1
* created 2019.02.03
* updated 2019.09.01 : makes checker pattern in color
*/

void setup() {

size(720, 720);
colorMode(HSB, 360.0, 100.0, 100.0, 100.0);
smooth();
noLoop();

}

void draw() {

int   lastFrameCnt = 24;
int   frameMax     = 24 * 6;
float baseHue      = random(360.0);

for (int frameCnt = 1; frameCnt < frameMax; ++frameCnt) {

background(0.0, 0.0, 90.0, 100);
noFill();
strokeWeight(1.0);

float easeRatio  = easeInOutCubic(map(frameCnt, 0, frameMax, 0.0, 1.0));
int   plotMax    = floor(10000 * easeRatio);
drawVectorfield(
baseHue,
5.0,
plotMax,
0.004
);
drawVectorfield(
baseHue + 30.0,
20.0,
plotMax,
0.002
);

casing((baseHue + 0.0) % 360.0);
saveFrame("frames/" + String.format("%04d", frameCnt) + ".png");

}

// to show the last frame in long time
for (int frameCnt = frameMax; frameCnt < frameMax + lastFrameCnt; ++frameCnt) {
saveFrame("frames/" + String.format("%04d", frameCnt) + ".png");
}

saveFrame("frames/0000.png");

exit();

}

/**
* drawVectorfield    : draw vector field
* @param  _baseHue   : square color.
* @param  _alpha     : square alpha.
* @param  _plotMax   : how many times to draw stroke.
* @param  _plotScale : vector field step.
*/
private void drawVectorfield(float _baseHue, float _alpha, int _plotMax, float _plotScale) {

int squareCnt = 0;
for (float xInit = 0.15; xInit <= 0.9; xInit += 0.05) {
for (float yInit = 0.15; yInit <= 0.9; yInit += 0.05) {

float xPrev = 0.0;
float yPrev = 0.0;
// using noise() as an array of random
float xCurr = xInit + map(noise(xInit * 3.0, yInit * 3.0), 0.0, 1.0, -0.03, 0.03);
float yCurr = yInit + map(noise(xInit * 7.0, yInit * 7.0), 0.0, 1.0, -0.03, 0.03);

float hueApply = _baseHue + noise(xInit, yInit) * 60.0;
if (squareCnt % 2 == 0) {
hueApply += 30.0;
}
squareCnt++;

for (int plotCnt = 0; plotCnt < _plotMax; ++plotCnt) {

// I don't know why this formula makes square shape...
xPrev += 0.25 * sin(TWO_PI * xCurr * 10.0);
yPrev += 0.25 * sin(TWO_PI * yCurr * 10.0);
xCurr += _plotScale * cos(TWO_PI * xPrev * 10.0);
yCurr += _plotScale * cos(TWO_PI * yPrev * 10.0);

stroke(
hueApply % 360.0,
map(plotCnt, 0, _plotMax, 80.0, 30.0),
map(plotCnt, 0, _plotMax, 30.0, 60.0),
_alpha
);
point(xCurr * width, yCurr * height);

}
}
}

}

/**
* casing : draw fancy casing
* @param  _baseHue : casing color.
*/
private void casing(float _baseHue) {

fill(0.0, 0.0, 0.0, 0.0);
strokeWeight(54.0);
stroke((_baseHue + 30.0) % 360.0, 80.0, 20.0, 100.0);
rect(0.0, 0.0, width, height);
strokeWeight(50.0);
stroke(0.0, 0.0, 100.0, 100.0);
rect(0.0, 0.0, width, height);
noStroke();
noFill();

}

/**
* easeInOutCubic easing function.
* @param  _t    0.0 - 1.0 : linear value.
* @return float 0.0 - 1.0 : eased value.
*/
private float easeInOutCubic(float _t) {
_t *= 2.0;
if (_t < 1.0) {
return pow(_t, 3) / 2.0;
}
_t -= 2.0;
return (pow(_t, 3) + 2.0) / 2.0;
}

/*

This program is free software: you can redistribute it and/or modify