Add this code at the bottom of your start() method.
In the spirit of helping people understand, here's how I figured this out. Since this is not only a 3D, but also a JavaFX application, I wizarded-up a JavaFX application from NetBeans IDE. I then added the package/class you created, and compared the two. The simplistic "Hello World" app from NetBeans did no 3d, but it did all the required stuff for a JavaFX app. I had written a JavaFX app or two earlier, but I would not have been facile enough to recognize the problem. It did seem, even at a superficial glance, that something was missing in the code.
I actually did copy your code below, into a NetBeans 8.0.2 IDE and run it. So, your code will work, if you add those lines at the bottom. It could be that the environment you are coding against is different than mine. Since there are missing methods from your Camera object, that could be the case.
You could try doing exactly what I did: save the text of your class (or the Java file) somewhere. Then go back into NetBeans 8.0.2, and create a new project with: "New Project/JavaFX/JavaFX Application". Then just make a world_3d_2 package. And then just copy your java file into that package's folder. Make sure your JDK is at least Java 1.8.
If it still fails, it could be that the JavaFX versions are different. I think mine is the one that came bundled with JDK 1.8 and NetBeans 8.0.2.