I created 2 model loaders, an MD2 and a RAW Faces model loader. The MD2 model loader can do animations. The RAW model loader can't do animations. I use a factory method to get an instance of the model, for example:

model = modelFactory.LoadModel("test.md2");
or
model = modelFactory.LoadModel("test.raw");

I can then access the methods that apply for both types, such as Draw(); However, if the model is in MD2 format I want to use the Play() (play animation) method. But I'm talking to an interface and can't access it. I want that, if the model is an MD2 I can use the Play() method, but if it's an RAW, the method shouldn't be available. How can I access the method Play()? Do I use the right pattern?

Your factory method is creating objects that implement an interface. Therefore, if you want to take objects from that factory and use methods outside of that interface, you are using the wrong factory method.

Either:
- extend the interface to provide the method you want (eg. make Play() exist for RAW, but do nothing)
- create a new interface (eg. AnimatedModel) with the extra method, and a new factory method that only creates AnimatedModels. (This would fail if passed "test.raw".)