code: public boolean intersect(Envelope3D other) {
  		if (isEmpty() || other.isEmpty())
  			return false;
  
  		if (other.xmin > xmin)
  			xmin = other.xmin;
  
  		if (other.xmax < xmax)
  			xmax = other.xmax;
  
  		if (other.ymin > ymin)
  			ymin = other.ymin;
  
  		if (other.ymax < ymax)
  			ymax = other.ymax;
  
  		if (other.zmin > zmin)
  			zmin = other.zmin;
  
  		if (other.zmax < zmax)
  			zmax = other.zmax;
  
  		boolean bIntersecting = xmin <= xmax && ymin <= ymax && zmin <= zmax;
  
  		if (!bIntersecting)
  			setEmpty();
  
  		return bIntersecting;
  	}
docs: Intersects this envelope with the other and stores result in this
  envelope.
  
  @return True if this envelope intersects the other, otherwise sets this
  envelope to empty state and returns False.