Chapter 13: Example 13-6: Oscillation

// Learning Processing
// Daniel Shiffman
// http://www.learningprocessing.com

// Example 13-6: Oscillation

float theta = 0.0;

void setup() {
  size(200,200);
  smooth();
}


void draw() {
  background(255);
  
  // The output of the sin() function oscillates smoothly between 1 and 1. 
  // By adding 1 we get values between 0 and 2. 
  // By multiplying by 100, we get values between 0 and 200 which can be used as the ellipse's x location.
  float x = (sin(theta) + 1) * width/2; 
  
  // With each cycle, increment theta
  theta += 0.05;
  
  // Draw the ellipse at the value produced by sine
  fill(0);
  stroke(0);
  line(width/2,0,x,height/2);
  ellipse(x,height/2,16,16);
}