class OkuboTank extends Universe {

  vector laserPos = new vector(0,0,0);
  float laserWidth = 0.004;
  
  OkuboTank(float x, float y, float z, float wd, float ht, float dp) {
    super(x,y,z,wd,ht,dp);
  }
  
  void draw() {
    // draw the laser light.
    // not as general as the other code: assumes a straight-on x-z plot.
    vector laserScrPos = pos2scr(laserPos);
    for (int i=floor(origin.x); i<ceil(origin.x+span.x); i++) {
      float a = exp(-pow(abs(i-laserScrPos.x)/span.x/laserWidth,1.5));
      if (a>0.01) {
        stroke(255,255,255,200*a);
        line(i, origin.y, i, origin.y+span.y);
      }
    }
  }
  
}


class Universe {
  // a coordinate system, maybe more.
  
  vector origin, span; // location and size on screen
  vector modelMin, modelMax;
  
  Universe(float x, float y, float z, float wd, float ht, float dp) {
    // location on screen
    origin = new vector(x,y,z);
    span = new vector(wd,ht,dp);
    // by default, all coordinates range -1..1 in model units
    modelMin = new vector(-1,-1,-1);
    modelMax = new vector(1,1,1);
  }
  
  
  vector pos2scr(vector pos) { // position in model units to screen position
    return origin.plus((pos.minus(modelMin)).dividedBy(modelMax.minus(modelMin)).times(span));
  }
  
  vector scr2pos(vector scr) { // screen position to model position
    return modelMin.plus((scr.minus(origin)).dividedBy(span).times(modelMax.minus(modelMin)));
  }
  
  void draw() {}
  
}