a port of the Processing Visualization Language


Based on code from Keith Peters (www.bit-101.com). A segmented line follows the mouse. The relative angle from each segment to the next is calculated with atan2() and the position of the next is calculated with sin() and cos().

Original Processing.org Example: Follow3

// All Examples Written by Casey Reas and Ben Fry

// unless otherwise stated.

float[] x = new float[20];

float[] y = new float[20];

float segLength = 9;

void setup() {

  size(200, 200);



  stroke(0, 100);


void draw() {


  dragSegment(0, mouseX, mouseY);

  for(int i=0; i<x.length-1; i++) {

    dragSegment(i+1, x[i], y[i]);



void dragSegment(int i, float xin, float yin) {

  float dx = xin - x[i];

  float dy = yin - y[i];

  float angle = atan2(dy, dx);  

  x[i] = xin - cos(angle) * segLength;

  y[i] = yin - sin(angle) * segLength;

  segment(x[i], y[i], angle);


void segment(float x, float y, float a) {


  translate(x, y);


  line(0, 0, segLength, 0);


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