Debugging source

I've been looking at doing some work with the 3rd person camera. While I've been debugging through the application, I can get a pointer to an object that I have a collision with via

SceneObject *obj = collision.object;

Now, using the debugger I can view all members of this object and the very first member reads [InteriorInstance]. I can then view all the members of this InteriorInstance. However, I cannot figure how to get to this data programmatically. I've tried using the InteriorInstance class and I was able to cast my SceneObject to an InteriorInstance object with

InteriorInstance *interior = (InteriorInstance*)obj;

which seemed to do the trick before I tried using that pointer. Yet I cannot do anything with it. I keep recieving compiler errors stating:

"h:\Dev\realmwars\engine\game\shapeBase.cc(1675): error C2027: use of undefined type 'InteriorInstance'"

Yet I only get this with the code. I added getMaterialList to return the mMaterialMaps member.

Vector matList = interior->getMaterialList();

Can anyone instruct me on how we can access this data normally? I'll keep plugging away at it but any insight on how to access this data would be greatly appreciated.