Vector Math

/**
 * Vector
 * by Daniel Shiffman.
 *
 * Demonstration of some basic vector math: subtraction,
 * normalization, scaling. Normalizing a vector sets
 * its length to 1.
 */

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

void draw() {
  background(0);

  // A vector that points to the mouse location
  PVector mouse(mouseX, mouseY);

  // A vector that points to the center of the window
  PVector center(width/2, height/2);

  // Subtract center from mouse which results in a
  // vector that points from center to mouse
  mouse.sub(center);

  // Normalize the vector
  mouse.normalize();

  // Multiply its length by 150 (Scaling its length)
  mouse.mult(150);

  translate(width/2, height/2);
  // Draw the resulting vector
  stroke(255);
  strokeWeight(4);
  line(0, 0, mouse.x, mouse.y);
}