只处理整数和浮点数时得到NAN

I am working on an opengl assignment where I have to make a creature (I chose a snowman) move around some terrain. I am trying to make it move around, and I am getting the strangest errors. After printing the numbers out, I frequently get "-1.#QNAN0" as a number. I don't even know what that means. Below is the snowman's update function, constructor, and the header file. I am trying to get 2 numbers to use as velocity and add them to the position while it is set to animate (randomly changing), but I don't understand what errors are causing me to not get numbers out of rand().I am working on an opengl assignment where I ha