Smoothing s=new Smoothing();

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

void draw(){
  background(255);
  float a=s.interpolate("cubicInOut",0,TWO_PI,frameCount%100,100);
  line(width/2,height/2,width/2+cos(a)*width/2,height/2+sin(a)*height/2);
}