int bgcolor = 0x888888;
PFont font;
float diameter = 100;
float radius = 50;
float centerX = 100;
float centerY = 100;
float x = 0.0f;
float y = 0.0f;
float angle = 0.0f;
float frequency = 2.0f;
int counter = 0;
int[] coordsX = new int[360/(int)frequency];
int[] coordsY = new int[360/(int)frequency];

void setup()
{
  size(400, 250);
  background(bgcolor);
  
  font = createFont("Arial", 24);
  textFont(font);
}

void draw()
{
  background(bgcolor);
  
  // calculate point
  x = centerX + cos(radians(angle)) * radius;
  y = centerY + sin(radians(angle)) * radius;
  
  // draw circle
  noStroke();
  fill(255);
  ellipse(centerX, centerY, diameter, diameter);
  
  // draw point
  fill(0);
  ellipse(x, y, 10, 10);
  
  ellipse(centerX + radius + counter, y, 10, 10);
  
  stroke(255);
  for(int i = 0; i < counter; ++i)
     point(coordsX[i], coordsY[i]); 

  stroke(#aaaaaa);
   line(x, y, centerX + radius + counter, y);
  
  // adjust counter and angle
  coordsX[counter] = (int)(centerX + radius + counter);
  coordsY[counter] = (int)y;
  
  ++counter;
  angle -= frequency;
  if(angle <= -360)
  {
    angle = 0;
    counter = 0;
  }
  
  // output text coordinates
  //fill(255);
  //text("x = " + (int)x, 60, 190);
  //text("y = " + (int)y, 60, 220);
  //text("angle = " + (int)angle, 200, 220);
}