code: private Vertex interpolate(Vertex start, Vertex end, double t)
  	{
  		double x = interpolate(start.getX(), end.getX(), t);
  		double y = interpolate(start.getY(), end.getY(), t);
  		double z = interpolate(start.getZ(), end.getZ(), t);
  
  		return new Vertex(x, y, z);
  	}
docs: Interpolate the place of a {@link Vertex} between two.
  
  @param start the start
  @param end the end
  @param t the t
  @return the vertex