This example is for Processing 3+. If you have a previous version, use the examples included with your software. If you see any errors or have suggestions, please let us know.

Morph.

Changing one shape into another by interpolating vertices from one to another


// Two ArrayLists to store the vertices for two shapes
// This example assumes that each shape will have the same
// number of vertices, i.e. the size of each ArrayList will be the same
ArrayList<PVector> circle = new ArrayList<PVector>();
ArrayList<PVector> square = new ArrayList<PVector>();

// An ArrayList for a third set of vertices, the ones we will be drawing
// in the window
ArrayList<PVector> morph = new ArrayList<PVector>();

// This boolean variable will control if we are morphing to a circle or square
boolean state = false;

void setup() {
  size(640, 360);

  // Create a circle using vectors pointing from center
  for (int angle = 0; angle < 360; angle += 9) {
    // Note we are not starting from 0 in order to match the
    // path of a circle.  
    PVector v = PVector.fromAngle(radians(angle-135));
    v.mult(100);
    circle.add(v);
    // Let's fill out morph ArrayList with blank PVectors while we are at it
    morph.add(new PVector());
  }

  // A square is a bunch of vertices along straight lines
  // Top of square
  for (int x = -50; x < 50; x += 10) {
    square.add(new PVector(x, -50));
  }
  // Right side
  for (int y = -50; y < 50; y += 10) {
    square.add(new PVector(50, y));
  }
  // Bottom
  for (int x = 50; x > -50; x -= 10) {
    square.add(new PVector(x, 50));
  }
  // Left side
  for (int y = 50; y > -50; y -= 10) {
    square.add(new PVector(-50, y));
  }
}

void draw() {
  background(51);

  // We will keep how far the vertices are from their target
  float totalDistance = 0;
  
  // Look at each vertex
  for (int i = 0; i < circle.size(); i++) {
    PVector v1;
    // Are we lerping to the circle or square?
    if (state) {
      v1 = circle.get(i);
    }
    else {
      v1 = square.get(i);
    }
    // Get the vertex we will draw
    PVector v2 = morph.get(i);
    // Lerp to the target
    v2.lerp(v1, 0.1);
    // Check how far we are from target
    totalDistance += PVector.dist(v1, v2);
  }
  
  // If all the vertices are close, switch shape
  if (totalDistance < 0.1) {
    state = !state;
  }
  
  // Draw relative to center
  translate(width/2, height/2);
  strokeWeight(4);
  // Draw a polygon that makes up all the vertices
  beginShape();
  noFill();
  stroke(255);
  for (PVector v : morph) {
    vertex(v.x, v.y);
  }
  endShape(CLOSE);
}