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。