// Moving along curves 
// by REAS <http://reas.com> 

// Variables for first ellipse 
int e1_size = 18; 
float e1_x, e1_y = 0; 
float e1_speed = 1.0; 
int e1_direction = 1; 
 
// Variables for second ellipse 
int e2_size = 10; 
float e2_x, e2_y = 0; 
float e2_speed = 0.80; 
int e2_direction = 1; 
 
// Variables for third ellipse 
int e3_size = 14; 
float e3_x, e3_y = 0; 
float e3_speed = 0.65; 
int e3_direction = 1; 
 
 
void setup() 
{ 
  size(200, 200); 
  stroke(102); 
  ellipseMode(CENTER); 
  smooth(); 
  framerate(30); 
} 
 
void draw() 
{ 
  background(0); 
  
  stroke(102); 
  
  beginShape(LINE_STRIP); 
  for(int i=0; i<width; i++) { 
   vertex(i, singraph((float)i/width)*height); 
  } 
  endShape(); 
  
  beginShape(LINE_STRIP); 
  for(int i=0; i<width; i++) { 
   vertex(i, quad((float)i/width)*height); 
  } 
  endShape(); 
  
  beginShape(LINE_STRIP); 
  for(int i=0; i<width; i++) { 
   vertex(i, hump((float)i/width)*height); 
  } 
  endShape(); 
  
  e1_x += e1_speed * e1_direction; 
  if (e1_x > width || e1_x < 0) { 
    e1_direction = e1_direction * -1; 
  } 
  e1_y = singraph((float)e1_x/width)*height; 
  noStroke(); 
  fill(255); 
  ellipse(e1_x, e1_y, e1_size, e1_size); 
  
  e2_x += e2_speed * e2_direction; 
  if (e2_x > width || e2_x < 0) { 
    e2_direction = e2_direction * -1; 
  } 
  e2_y = quad((float)e2_x/width)*height; 
  noStroke(); 
  fill(255); 
  ellipse(e2_x, e2_y, e2_size, e2_size); 
  
  e3_x += e3_speed * e3_direction; 
  if (e3_x > width || e3_x < 0) { 
    e3_direction = e3_direction * -1; 
  } 
  e3_y = hump((float)e3_x/width)*height; 
  noStroke(); 
  fill(255); 
  ellipse(e3_x, e3_y, e3_size, e3_size); 
} 
 
float singraph(float sa) { 
  sa = (sa - 0.5) * 1.0; //scale from -1 to 1 
  sa = sin(sa*PI)/2 + 0.5; 
  return sa; 
} 
 
float quad(float sa) { 
  return sa*sa*sa*sa; 
} 
 
float hump(float sa) { 
  sa = (sa - 0.5) * 2; //scale from -2 to 2 
  sa = sa*sa; 
  if(sa > 1) { sa = 1; } 
  return 1-sa; 
}