Creating a database

This is a discussion on Creating a database within the Game Programming forums, part of the General Programming Boards category; Actually the object base class implements all of its methods to the best of it's ability. I have encountered the ...

  1. #16
    Super Moderator VirtualAce's Avatar
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    Actually the object base class implements all of its methods to the best of it's ability.

    I have encountered the same problem you have in my system at times. Let's say I have materials for objects. The material properties applied to an object determine how light interacts with the object. This is a resource but it is an engine resource not a game resource. So the first derivation of objects is just that. I have resource objects and then game objects. Keeping the two separate has been much easier than lumping them together.

    Now I know this means you will have 2 derivations before you actually get to the specific objects, but it makes things a lot easier conceptually and architecturally. I hate having 2 derivations but I've not found a good way to get around it.

    So in short my core engine setup:

    Engine architecture
    Resources
    • CResource - Resource base class
    • CMaterial - (D3DMATERIAL9)
    • CShader - (ID3DXEffect)
    • CLight - (D3DLIGHT9)
    • CTexture - (IDirect3DTexture9)
    • CD3DXMesh - (ID3DXMesh)
    • CD3DXProgMesh - (ID3DXPMesh)
    • CAnimFrame - animation frame class

    Resource managers
    • CResMgr - Resource manager base class
    • CMatlMgr - Materials manager
    • CShaderMgr - Shader manager
    • CLightMgr - Light manager
    • CTexMgr - Texture manager
    • CD3DXMeshMgr - Model mesh manager
    • CD3DXProgMeshMgr - Model progressive mesh manager
    • CAnimSeq - animation sequence class - animation frame container class


    Sound engine resources
    • CDXSoundSegment - (IDirectMusicSegment8,IDirectMusicSegmentState8)
    • CDXAudioPath - (IDirectMusicAudioPath8)
    • CDXSoundEmitter - container class for sound segments - each emitter can have any number of sounds associated with it and each play on separate audio paths


    Script support
    • ScriptCmn.h - script support common header file
    • CScriptVarMgr - Script variable container class


    Utility classes
    • CCamera - 3D camera support (cockpit/first person, chase, object, flyby, and free floating camera support)
    • COrient3D - controls all 3D orientations for all objects
    • CINIReader - reads ini files in form [Header] Key=Value
    • CTimer - timer class


    Engine objects (non-game specific)
    • CSkyBox - skybox support
    • CBillboard - billboarding support
    • CSprite - sprite class (uses a CAnimSeq)
    • CSkySphere - spherical skybox support (also textured sphere support)


    Core engine classes
    • CD3DApp - Direct3D application base class
    • CD3DView - Direct3D view class (not quite implemented fully)
    • CDXAudio - DirectMusic base class
    • CDXInput - DirectInput base class
    • CDXShowWnd - DirectShow base class
    • CKeyboard - keyboard device class
    • CMouse - mouse device class
    • CGamePad - stick/pad device class


    Debug
    • CEngineException - exception handling class
    • CMemCheck - memory checking class (not fully implemented)


    This is a small list of the basic engine classes. An actual game coded with the engine would have many more object and game specific classes.

    I'm not sure what you mean by a database but since all of my base classes can stream to disk, all of the derived classes inherit that support and/or can override the base implementation if needed.

    Either you are going to create tons of template classes for managers or you are going to create tons of separate manager classes. Either way all objects cannot just be lumped into one huge container because they are so different from one another. My actual game code classes for my space project and for the Zelda project are also quite numerous but they derive from these. This is what I would consider my core engine code and I would like to keep it separate from game specific data and objects.

    I was going to create a memory and file resource class but found that both of those were so simple they were not needed. Plus any memory class I come up with is probably not going to be faster than just using new and delete.
    I also wanted to create an archive class but it proved to be a bit more difficult than I first thought.

    The simple way to do object serialization is to take the MFC approach. If your base resource class has a Serialize() function or WriteToDisk() ReadFromDisk() then you can just make it a pure virtual. This means it will have to be implemented in derived classes and you cannot instantiate the base. Since the base object has no way of knowing how to write the object to disk I recommend this approach. So in your derived classes you simply code the virtual function specific to your object.

    Code:
    
    ...
    CShipMgr *pShipMgr=new CShipMgr();
    pShipMgr->AddFromINI(m_spDevice,"INI\\Ships\\Ships.ini","Terran")
    CArchiveFile *pFile=new CArchiveFile("TerranShips",WRITE_ONLY);
    CArchiver *pArchive=new CArchiver(pFile,CArchiver::WRITE);
    pShipMgr->Serialize(pArchive)
    
    ...
    ...
    
    //CShipMgr derived from CResMgr which has pure virtual Serialize(CArchiver *pArchiver)
    void CShipMgr::Serialize(CArchiver *pArchiver)
    {
      if (pArchiver->IsStoring())
      {
         //Write data to stream
      }
      else
      {
         //Read data from stream
      }
    }
    As I said this is not quite complete yet since CArchiver has been proving to be a pain in the rump.
    Last edited by VirtualAce; 06-10-2007 at 01:32 AM.

  2. #17
    Absent Minded Programmer
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    I see, well I wonder...

    With the create method in the object base class, what can we possibly implement when we don't know what kind of data the object stores?

    Like you were saying, when you create a new object it could be a material, or a mesh, or a sound.. Each of these objects have completely different variables and such, like vertices or a sound file... or lighting details... They have absolutely nothing in common.. What could I implement in the create function that would be universal to all objects?

    The same goes for the delete method. Perhaps we can access all of the objects via pointer, but that is also handled by the manager class, it returns a pointer to a raw object.

    Unless the access method is ment to return the data contained in each specific object class, such as an array of vertices or something like that, which would be useful. So then again none of that data is ever the same, none of it is in common. Really only the abstract idea of the methods in the object base class are the same.
    Sometimes I forget what I am doing when I enter a room, actually, quite often.

  3. #18
    Super Moderator VirtualAce's Avatar
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    Create would be virtual. Implement it in the derived object classes. You could implement creation in the constructor but then you get into lots of exceptions being thrown but it does follow RAII.

    You are creating interfaces for your derived objects. This ensures that your derived objects implement some type of standard interfaces/functions for each object and manager. These are not interfaces such as COM interfaces but the principle is somewhat the same.

  4. #19
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    I guess the only problem now is making it so my objects can be serialized and deserialized. Especially Menu objects.

    But that post is in the C++ forums.
    Sometimes I forget what I am doing when I enter a room, actually, quite often.

  5. #20
    Super Moderator VirtualAce's Avatar
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    Well you can create your own archive system. How you approach that is up to you.

    I recommend creating a file class and an archive class to keep them separate much like MFC does.

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