我正在做一个游戏，我可以/应该创建一个“敌人”课程吗？

Question

I'm making a game for my final project in an XNA class I'm taking, it's going to be a FPS. In order to generate enemies, I figured that I could write a class that imports a model and defines the random size and placement of the "Enemy", as well as his movements and actions. I would then call that class from my Game.cs file. However, I'm having some difficulty with this.

My main issue is that I'm not sure where/how to call the Enemy (which is a snowman) in the Game file.

Here's what I have for the Snowmen.cs (enemy) class

public class Snowmen : Microsoft.Xna.Framework.Game
{
    private Camera  cam = new Camera();

    Model snowMan;
    Matrix[] snowManMatrix;

    protected override void LoadContent()
    {
        snowMan = Content.Load<Model>( "Models\\snowman" );
        snowManMatrix = new Matrix[ snowMan.Bones.Count ];
        snowMan.CopyAbsoluteBoneTransformsTo( snowManMatrix );
    }

    public void DrawSnowMan(Model model, GameTime gameTime) 
    {
        foreach (ModelMesh mesh in model.Meshes) 
        {
            Matrix world, scale, translation;

            scale = Matrix.CreateScale(0.02f, 0.02f, 0.02f);
            translation = Matrix.CreateScale(0.0f, 0.7f, -4.0f);

            world = scale * translation;

         foreach (BasicEffect effect in mesh.Effects)
         {
            effect.World = snowManMatrix[mesh.ParentBone.Index] * world;

            effect.View = cam.viewMatrix;
            effect.Projection = cam.projectionMatrix;
            effect.EnableDefaultLighting();
         }

           mesh.Draw();
         }
    }

    protected override void Draw(GameTime gameTime)
    {
        DrawSnowMan( snowMan, gameTime ); 
        base.Draw(gameTime);
    }
}

As of right now, My Game1.cs file is a functional skybox and also contains LoadContent() and Draw() methods. Is the enemy class completely unnecessary?

Answer 1

You would probably want to use a DrawableGameObject

public class Snowman : DrawableGameObject
{
    private Camera  cam = new Camera();

    //Model snowMan;
    //Matrix[] snowManMatrix;

    public Model snowMan {get;set;};
    public Matrix[] snowManMatrix{get;set;};

    protected override void LoadContent()
    {
        //snowMan = Content.Load<Model>( "Models\\snowman" );
        snowManMatrix = new Matrix[ snowMan.Bones.Count ];
        snowMan.CopyAbsoluteBoneTransformsTo( snowManMatrix );
    }

    public void DrawSnowMan(Model model, GameTime gameTime) 
    {
        foreach (ModelMesh mesh in model.Meshes) 
        {
            Matrix world, scale, translation;

            scale = Matrix.CreateScale(0.02f, 0.02f, 0.02f);
            translation = Matrix.CreateScale(0.0f, 0.7f, -4.0f);

            world = scale * translation;

         foreach (BasicEffect effect in mesh.Effects)
         {
            effect.World = snowManMatrix[mesh.ParentBone.Index] * world;

            effect.View = cam.viewMatrix;
            effect.Projection = cam.projectionMatrix;
            effect.EnableDefaultLighting();
         }

           mesh.Draw();
         }
    }

    protected override void Draw(GameTime gameTime)
    {
        DrawSnowMan( snowMan, gameTime ); 
    }
}

In Game1.cs

Initialize

   Snowman snowDude= new Snowman();
   Components.Add(snowDude);

And move

   //snowDude = Content.Load<Model>( "Models\\snowman" ); 
   snowDude.snowMan = Content.Load<Model>( "Models\\snowman" ); 

into Game1's LoadContent

Adding to Components means that snowDude's Update and Draw are called whenever Game1's is. I am honestly not 100% on in what order though. I believe Load Content should be called as well but I think it is better practice (at least while you're learning) to import all of your sounds/animations/sprites in the same place (in your main file) so that you know exactly what is being called and when.

OR instead of Components.Add(snowDude);

You can just call snowDude.Draw(gametime) in Game1's Draw Method. and snowDude.Update() in Game1's Update method.

And otherwise I agree with Brent. If there are only Snowmen then you should be fine with only one class but if you start adding more there will be a lot of overlap, so making an Enemy Class

public class Enemy: DrawableGameObject{}

and changing SnowMan to

public class SnowMan:Enemy{}

should be appropriate.

Answer 2

If you only have snowmen than this is fine. When you add other enemies, or similar objects then adding a Parent class such as Enemy is useful both structurally, and it allows you to centralize your code and reduce/eliminate duplicate code.

Answer 3

If you expect your game to grow considerably, you might consider an entity system:

http://cowboyprogramming.com/2007/01/05/evolve-your-heirachy/

http://t-machine.org/index.php/2007/09/03/entity-systems-are-the-future-of-mmog-development-part-1/

An entity system can help you overcome some of the design challenges inherent in traditional object-oriented solutions (Deep hierarchies, god objects, etc.) as well as keep your game flexible in the face of change.