final int W = 400; final int H = 400;
  float x = 0;  float y = 200;   
  int i = 0;
  
void setup(){
  size( W, H );
  strokeWeight(2);
  background( #FFFFFF );
}
public void line3D( float x, float y, float z ){
  int a = round( x + y/2 );
  int b = H - round( y/2 );
  int c = b - round(z);
  stroke( 0, 0, 127, 20 );    line( a, b, a, c  );
  stroke( 0, 255, 127, 20 );  line( a+2, b, a+2, c  );
  stroke( 255, 0, 127, 20 );  line( a, c-2, a+2, c  );
}
public void draw(){
  x++; 
  if (x > 100){ y--; x=0; }
  line3D( round(x*2), round(y*2), cos(x/20)*sin(y/20)*100+100 );
  if (i < 10000) i++; else noLoop();
}