int pts = 40; 
  float angle = 0;
  float radius = 60.0;
  
  // lathe segments
  int segments = 60;
  float latheAngle = 0;
  float latheRadius = 100.0;
  
  //vertices
  PVector vertices[], vertices2[];
  
  // for shaded or wireframe rendering 
  boolean isWireFrame = false;
  
  // for optional helix
  boolean isHelix = false;
  float helixOffset = 5.0;
  
  void setup(){
    size(640, 360, P3D);
  }
  
  void draw(){
    background(50, 64, 42);
    // basic lighting setup
    lights();
    // 2 rendering styles
    // wireframe or solid
    if (isWireFrame){
      stroke(255, 255, 150);
      noFill();
    } 
    else {
      noStroke();
      fill(150, 195, 125);
    }
    //center and spin toroid
    translate(width/2, height/2, -100);
  
    rotateX(frameCount*PI/150);
    rotateY(frameCount*PI/170);
    rotateZ(frameCount*PI/90);
  
    // initialize point arrays
    vertices = new PVector[pts+1];
    vertices2 = new PVector[pts+1];
  
    // fill arrays
    for(int i=0; i<=pts; i++){
      vertices[i] = new PVector();
      vertices2[i] = new PVector();
      vertices[i].x = latheRadius + sin(radians(angle))*radius;
      if (isHelix){
        vertices[i].z = cos(radians(angle))*radius-(helixOffset* 
          segments)/2;
      } 
      else{
        vertices[i].z = cos(radians(angle))*radius;
      }
      angle+=360.0/pts;
    }
  
    // draw toroid
    latheAngle = 0;
    for(int i=0; i<=segments; i++){
      beginShape(QUAD_STRIP);
      for(int j=0; j<=pts; j++){
        if (i>0){
          vertex(vertices2[j].x, vertices2[j].y, vertices2[j].z);
        }
        vertices2[j].x = cos(radians(latheAngle))*vertices[j].x;
        vertices2[j].y = sin(radians(latheAngle))*vertices[j].x;
        vertices2[j].z = vertices[j].z;
        // optional helix offset
        if (isHelix){
          vertices[j].z+=helixOffset;
        } 
        vertex(vertices2[j].x, vertices2[j].y, vertices2[j].z);
      }
      // create extra rotation for helix
      if (isHelix){
        latheAngle+=720.0/segments;
      } 
      else {
        latheAngle+=360.0/segments;
      }
      endShape();
    }
  }
  
  /*
   left/right arrow keys control ellipse detail
   up/down arrow keys control segment detail.
   'a','s' keys control lathe radius
   'z','x' keys control ellipse radius
   'w' key toggles between wireframe and solid
   'h' key toggles between toroid and helix
   */
  void keyPressed(){
    if(key == CODED) { 
      // pts
      if (keyCode == UP) { 
        if (pts<40){
          pts++;
        } 
      } 
      else if (keyCode == DOWN) { 
        if (pts>3){
          pts--;
        }
      } 
      // extrusion length
      if (keyCode == LEFT) { 
        if (segments>3){
          segments--; 
        }
      } 
      else if (keyCode == RIGHT) { 
        if (segments<80){
          segments++; 
        }
      } 
    }
    // lathe radius
    if (key =='a'){
      if (latheRadius>0){
        latheRadius--; 
      }
    } 
    else if (key == 's'){
      latheRadius++; 
    }
    // ellipse radius
    if (key =='z'){
      if (radius>10){
        radius--;
      }
    } 
    else if (key == 'x'){
      radius++;
    }
    // wireframe
    if (key =='w'){
      if (isWireFrame){
        isWireFrame=false;
      } 
      else {
        isWireFrame=true;
      }
    }
    // helix
    if (key =='h'){
      if (isHelix){
        isHelix=false;
      } 
      else {
        isHelix=true;
      }
    }
  }