XNA之RPG游戏开发教程之五

上一节我们说到游戏中的地图绘制，我们在TileMap类中为GameplayScreen绘制地图，但要模拟真实的游戏地图，需要做到地图的滚动，以前我们经常会用现成的图片，利用图片的滚动模拟背景移动。现在要实现游戏地图的个性化，要用Tile绘制地图,就需要一个2D的Camera类，站在player的Position上会有一个视野范围，就在这个视野范围内绘制地图，用这种方法来实现动态地图的模拟。接下来建立一个Camera类如下

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using Microsoft.Xna.Framework;

using Microsoft.Xna.Framework.Graphics;

using Microsoft.Xna.Framework.Input;

namespace XRpgLibrary.TileEngine

{

public class Camera

 {

 #region Field Region

Vector2 position;//Camera位置

float speed;//Camera的移动速度

float zoom;//Camera的放大缩小倍数

Rectangle viewportRectangle;

 #endregion

 #region Property Region

public Vector2 Position

 {

get { return position; }

private set { position = value; }

 }

public float Speed

 {

get { return speed; }

set

 {

 speed = (float)MathHelper.Clamp(speed, 1f, 16f);//该函数的作用是将speed值限定在1和16之间，大于16，返回16，小于1，返回1，在两者之间返回true

 }

 }

public float Zoom

 {get { return zoom; }

 }

 #endregion

 #region Constructor Region

public Camera(Rectangle viewportRect)//用视野矩阵来初始化相机

 {

 speed = 4f;

 zoom = 1f;

 viewportRectangle = viewportRect;

 }

public Camera(Rectangle viewportRect, Vector2 position)

 {

 speed = 4f;

 zoom = 1f;

 viewportRectangle = viewportRect;

 Position = position;

 }

 #endregion

 #region Method Region//根据键盘控制移动，实际上将Camera与Player联系在一起

public void Update(GameTime gameTime)

 {

if (InputHandler.KeyDown(Keys.Left))

 position.X -= speed;

else if (InputHandler.KeyDown(Keys.Right))

 position.X += speed;

if (InputHandler.KeyDown(Keys.Up))

 position.Y -= speed;

else if (InputHandler.KeyDown(Keys.Down))

 position.Y += speed;

 }

 #endregion

 }

}

接下来就是为游戏中添加玩家player类

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using Microsoft.Xna.Framework;

using Microsoft.Xna.Framework.Graphics;

using Microsoft.Xna.Framework.Input;

using XRpgLibrary;

using XRpgLibrary.TileEngine;

namespace EyesOfTheDragon.Components

{

public class Player

 {

 #region Field Region

Camera camera;//Camera对象，将其与玩家联系起来

Game1 gameRef;//Game对象，将其与玩家联系起来

 #endregion

 #region Property Region

public Camera Camera

 {

get { return camera; }

set { camera = value; }

 }

 #endregion

 #region Constructor Region在构建玩家的同时构建Camera

public Player(Game game)

 { 
 gameRef = (Game1)game;

 camera = new Camera(gameRef.ScreenRectangle);

 }

 #endregion

 #region Method Region

public void Update(GameTime gameTime)

 {

 camera.Update(gameTime);

 }

public void Draw(GameTime gameTime, SpriteBatch spriteBatch)

 {

 }

 #endregion

 }

}

接着就是将Player对象添加到GamePlayScreen中去，这样就会为游戏页面实例化一个玩家对象，同时实例化一个Camera对象来实现地图的滚动

using EyesOfTheDragon.Components;//添加空间引用

#region Field Region

Engine engine = new Engine(32, 32);

Tileset tileset; 

TileMap map;

Player player;//定义对象

#endregion

#region Constructor Region

public GamePlayScreen(Game game, GameStateManager manager)

 : base(game, manager)

{

 player = new Player(game);//构造函数中实例化对象

}

#endregion

在游戏页面的更新中也要更新玩家

public override void Update(GameTime gameTime)

{

 player.Update(gameTime);

 base.Update(gameTime);

}

接下来要更改的就是TileMap类，上节说过，该类是地图绘制的核心类，地图的绘制在Draw方法中实现，上节中是通过不断更改矩形变量destination的X,Y坐标来绘制每个tile，现在要用Camera来更新地图，所以要将Camera作为参数传入Draw方法中，由其来决定绘制tile的X,Y坐标，更新如下

public void Draw(SpriteBatch spriteBatch, Camera camera)

{

Rectangle destination = new Rectangle(0, 0, Engine.TileWidth, Engine.TileHeight);

Tile tile;

foreach (MapLayer layer in mapLayers)

 {

for (int y = 0; y < layer.Height; y++)

 {

  destination.Y = y * Engine.TileHeight - (int)camera.Position.Y;//获得绘制tile的Y坐标

for (int x = 0; x < layer.Width; x++)

 {

 tile = layer.GetTile(x, y);

if (tile.TileIndex == -1 || tile.Tileset == -1)

continue;

 destination.X = x * Engine.TileWidth - (int)camera.Position.X;//获得绘制tile的X坐标

 spriteBatch.Draw(

 tilesets[tile.Tileset].Texture,

 destination,

 tilesets[tile.Tileset].SourceRectangles[tile.TileIndex],

Color.White);

 }

 }

 }

}

这里关于游戏中摄像机的原理，自己解释不太清楚，可以从http://blog.csdn.net/beyondma/article/details/6766914这里获得相关的理论知识

到这里我们运行程序，移动Camera绘制地图，会发现有绘出地图的现象，即Camera移出了窗体边界。这就需要根据地图的大小来控制Camera的移动区域，需要在TileMap类中添加地图宽度，高度的对外属性，在Camera类中根据这些属性来控制Camera的移动区域，地图的左边和上边最好控制，只要保证Camera的Position的X,Y坐标都是非负就能保证其没有越过左边界和上边界，至于下边界和右边界就用地图的宽度和高度来控制

TileMap类中的更新代码如下

#region Field Region

List<Tileset> tilesets;

List<MapLayer> mapLayers;

static int mapWidth;//地图的宽度(tile的个数)

static int mapHeight;//地图的高度

#endregion

#region Property Region

public static int WidthInPixels返回地图宽度方向的像素值

{

  get { return mapWidth * Engine.TileWidth; }

}

public static int HeightInPixels

{

  get { return mapHeight * Engine.TileHeight; }

}

#endregion

#region Constructor Region

public TileMap(List<Tileset> tilesets, List<MapLayer> layers)

{

 this.tilesets = tilesets;

 this.mapLayers = layers;

 mapWidth = mapLayers[0].Width;//以游戏最底层的MapLayer的高度，宽度来初始化

 mapHeight = mapLayers[0].Height;

for (int i = 1; i < layers.Count; i++)

 {
  //检测到各个层之间的宽度，高度不一致，抛出异常

  if (mapWidth != mapLayers[i].Width || mapHeight != mapLayers[i].Height)

     throw new Exception("Map layer size exception");

 }

}

public TileMap(Tileset tileset, MapLayer layer)

{

 tilesets = new List<Tileset>();

 tilesets.Add(tileset);

 mapLayers = new List<MapLayer>(); 
 mapLayers.Add(layer);

 mapWidth = mapLayers[0].Width;//初始化

 mapHeight = mapLayers[0].Height;

}

#endregion

Camera类中的更新如下

public void Update(GameTime gameTime)

{

Vector2 motion = Vector2.Zero;//定义一个向量对象，用来确定Camera的移动方向

if (InputHandler.KeyDown(Keys.Left))

 motion.X = -speed;

else if (InputHandler.KeyDown(Keys.Right))

 motion.X = speed;

if (InputHandler.KeyDown(Keys.Up))

 motion.Y = -speed;

else if (InputHandler.KeyDown(Keys.Down))

 motion.Y = speed;

if (motion != Vector2.Zero)

 motion.Normalize();//对向量进行标准化，然后再乘以Speed才能真的模拟玩家的移动

 position += motion * speed;

 LockCamera();//对Camera的位置进行设定

}

private void LockCamera()

{

 position.X = MathHelper.Clamp(position.X,

 0,

TileMap.WidthInPixels - viewportRectangle.Width);//将Camera的X坐标限定在0和（地图宽度-Camera视野宽度）之间，特别注意要减去Camera视野宽度，这样就不会出现移出游戏窗体的现象

 position.Y = MathHelper.Clamp(position.Y,

 0,

TileMap.HeightInPixels - viewportRectangle.Height);

}

#endregion

最后我们要实现多层地图的绘制，首先要在TileMap类中添加一个AddLayer方法来添加一层地图

public void AddLayer(MapLayer layer)

{
//首先判断每层的宽度，高度是否相同

if (layer.Width != mapWidth && layer.Height != mapHeight)

throw new Exception("Map layer size exception");

 mapLayers.Add(layer);

}

接着就是在GamePlayScreen类中添加这一层地图

protected override void LoadContent()

{ 

 Texture2D tilesetTexture = Game.Content.Load<Texture2D>(@"Tilesets\tileset1");

 tileset = new Tileset(tilesetTexture, 8, 8, 32, 32);

 MapLayer layer = new MapLayer(40, 40);

for (int y = 0; y < layer.Height; y++)

 {

for (int x = 0; x < layer.Width; x++)

 {

  Tile tile = new Tile(0, 0);

  layer.SetTile(x, y, tile);

 }
 }

 map = new TileMap(tileset, layer);

 MapLayer splatter = new MapLayer(40, 40);

 Random random = new Random();
//在40*40的图层上添加80个tile对象

for (int i = 0; i < 80; i++)

 {

  int x = random.Next(0, 40);

  int y = random.Next(0, 40);
  //在2到14这些图片中随机选择一个

  int index = random.Next(2, 14);

  Tile tile = new Tile(index, 0);//利用tile索引来初始化tile对象

  splatter.SetTile(x, y, tile);//往新的图层上添加tile对象

 }

 map.AddLayer(splatter);

base.LoadContent();

}

接着我们想在游戏中添加一些除了草地，植物以为的城市tile，这就需要在GameplayScreen类中新添加一个tileset对象，将从 http://xnagpa.net/xna4/downloads/tilesets2.zip获得的tilesets2.png添加到Content中，更新GamePlayScreen的LoadContent()方法如下

protected override void LoadContent()

{

base.LoadContent();

  Texture2D tilesetTexture = Game.Content.Load<Texture2D>(@"Tilesets\tileset1");

 Tileset tileset1 = new Tileset(tilesetTexture, 8, 8, 32, 32);

 tilesetTexture = Game.Content.Load<Texture2D>(@"Tilesets\tileset2");

 Tileset tileset2 = new Tileset(tilesetTexture, 8, 8, 32, 32);//新建立的tileset对象

 List<Tileset> tilesets = new List<Tileset>();

 tilesets.Add(tileset1);

 tilesets.Add(tileset2);

MapLayer layer = new MapLayer(40, 40);
for (int y = 0; y < layer.Height; y++)

 {

for (int x = 0; x < layer.Width; x++)

 {

 Tile tile = new Tile(0, 0);

 layer.SetTile(x, y, tile);

 }

 }

 MapLayer splatter = new MapLayer(40, 40);

 Random random = new Random();

for (int i = 0; i < 80; i++)

 {

 int x = random.Next(0, 40);

 int y = random.Next(0, 40);

 int index = random.Next(2, 14);

 Tile tile = new Tile(index, 0);//这里的0代表的是第一个tileset集合

 splatter.SetTile(x, y, tile);

 }
//在第二个tileset集合中选择对象设定固定位置的tile

 splatter.SetTile(1, 0, new Tile(0, 1));

 splatter.SetTile(2, 0, new Tile(2, 1));

 splatter.SetTile(3, 0, new Tile(0, 1));

 List<MapLayer> mapLayers = new List<MapLayer>();

 mapLayers.Add(layer);

 mapLayers.Add(splatter);

 map = new TileMap(tilesets, mapLayers);

}

public override void Draw(GameTime gameTime)

{

 GameRef.SpriteBatch.Begin(

 SpriteSortMode.Immediate,

 BlendState.AlphaBlend,

 SamplerState.PointClamp,

 null,

 null,

 null,

 Matrix.Identity);

 map.Draw(GameRef.SpriteBatch, player.Camera);//绘制地图
base.Draw(gameTime);

 GameRef.SpriteBatch.End();

}

OK,今天主要是实现了利用摄像机原理来更新地图，同时实现了多层地图。