Use of PVector to make an object rotate at constant speed around an origin point

constant_circular_orbit.pde

// Constant circular orbit

PVector pos, zAxis;
float radius = 200, force = 10;

void setup() {
  size(600, 600);
  background(0);
  noStroke();
  pos = new PVector(radius, 0);
  zAxis = new PVector(0, 0, -1); // for clockwise direction
  // (0, 0, 1) for counter clockwise
}

void draw() {
  background(0);
  translate(width/2, height/2);

  // origin
  fill(100);
  ellipse(0, 0, 10, 10);

  // calculate tangential force at every new position
  PVector tangent = pos.cross( zAxis );
  tangent.normalize();
  tangent.mult(force); // determine the speed of rotation

  // update of position with tangential force
  pos.add(tangent);

  // remap position to radius of orbit 
  pos.normalize();
  pos.mult(radius);

  // drawing the rotating object
  fill(255, 0, 0);
  ellipse(pos.x, pos.y, 10, 10);
}