梦想成真 XNA (7) - 碰撞检测

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梦想成真 XNA (7) - 碰撞检测



作者:webabcd


介绍
XNA: 碰撞检测

  • 通过 AABB(Axis Aligned Bounding Box)实现碰撞检测算法
  • 通过 Rectangle 类实现碰撞检测算法



示例
1、AABB 算法的 Demo(按键盘 N 键加载此 Demo)
Component/Collision/AABB.cs

/*
 * AABB - Axis Aligned Bounding Box
 * 所谓的坐标轴对齐(Axis Aligned),指的是盒体与世界坐标轴平行,同时盒体的每个边(2D)或面(3D)都和一条坐标轴平行(垂直)
 * 
 * 本 Demo 用于演示通过 AABB 算法检测两个精灵是否发生了碰撞
 */

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;

namespace XNA.Component.Collision
{
    public class AABB : Microsoft.Xna.Framework.DrawableGameComponent
    {
        // 精灵绘制器
        SpriteBatch _spriteBatch;

        // 精灵对象
        Texture2D _sprite;

        // 精灵的位置(系统控制的)
        Vector2 _systemSpritePosition = new Vector2(600, 300);

        // 精灵的速度(系统控制的),单位:像素数/每帧
        int _systemSpriteSpeed = 6;

        // 精灵的位置(用户控制的)
        Vector2 _userSpritePosition = Vector2.Zero;

        // 精灵的速度(用户控制的),单位:像素数/每帧
        int _userSpriteSpeed = 6;

        // 是否发生了碰撞
        bool _collided = false;

        public AABB(Game game)
            : base(game)
        {

        }

        public override void Initialize()
        {
            base.Initialize();
        }

        protected override void LoadContent()
        {
            _spriteBatch = new SpriteBatch(Game.GraphicsDevice);
            _sprite = Game.Content.Load<Texture2D>("Image/Son");
        }

        public override void Update(GameTime gameTime)
        {
            // 如果系统控制的精灵和用户控制的精灵发生了碰撞,则停止动画
            if (!CheckCollision())
            {
                calcSystemSpritePosition();
                calcUserSpritePosition();
            }
            else
            {
                _collided = true;
            }

            base.Update(gameTime);
        }

        /// <summary>
        /// 检查系统控制的精灵和用户控制的精灵是否发生了碰撞(通过 AABB 算法)
        /// </summary>
        /// <returns>两个精灵是否发生了碰撞</returns>
        private bool CheckCollision()
        {
            /*
             * 盒体与世界坐标轴平行,同时盒体的每个边(2D)或面(3D)都和一条坐标轴平行
             * AABB 包围盒是由一个 Max 坐标和一个 Min 坐标组成的,算法如下
             */

            Vector2 systemSpriteMin = new Vector2(_systemSpritePosition.X, _systemSpritePosition.Y);
            Vector2 systemSpriteMax = new Vector2(_systemSpritePosition.X + _sprite.Width, _systemSpritePosition.Y + _sprite.Height);
            Vector2 userSpriteMin = new Vector2(_userSpritePosition.X, _userSpritePosition.Y);
            Vector2 userSpriteMax = new Vector2(_userSpritePosition.X + _sprite.Width, _userSpritePosition.Y + _sprite.Height);

            if (systemSpriteMin.X <= userSpriteMax.X && systemSpriteMin.Y <= userSpriteMax.Y && systemSpriteMax.X >= userSpriteMin.X && systemSpriteMax.Y >= userSpriteMin.Y)
                return true;

            return false;
        }

        // 计算用户控制的精灵的位置
        private void calcUserSpritePosition()
        {
            KeyboardState keyboardState = Keyboard.GetState();

            if (keyboardState.IsKeyDown(Keys.Left) && _userSpritePosition.X >= 0)
                _userSpritePosition.X -= _userSpriteSpeed;
            if (keyboardState.IsKeyDown(Keys.Right) && _userSpritePosition.X <= Game.Window.ClientBounds.Width - _sprite.Width)
                _userSpritePosition.X += _userSpriteSpeed;
            if (keyboardState.IsKeyDown(Keys.Up) && _userSpritePosition.Y >= 0)
                _userSpritePosition.Y -= _userSpriteSpeed;
            if (keyboardState.IsKeyDown(Keys.Down) && _userSpritePosition.Y <= Game.Window.ClientBounds.Height - _sprite.Height)
                _userSpritePosition.Y += _userSpriteSpeed;

        }

        // 计算系统控制的精灵的位置
        private void calcSystemSpritePosition()
        {
            // 系统控制的精灵在 Y 轴方向上做往复运动
            _systemSpritePosition.Y += _systemSpriteSpeed;

            if (_systemSpritePosition.Y > Game.Window.ClientBounds.Height - _sprite.Height || _systemSpritePosition.Y < 0)
                _systemSpriteSpeed *= -1;
        }

        public override void Draw(GameTime gameTime)
        {
            if (_collided)
                Game.GraphicsDevice.Clear(Color.IndianRed);
            else
                Game.GraphicsDevice.Clear(Color.CornflowerBlue);

            // 在指定的位置上绘制精灵
            _spriteBatch.Begin();
            _spriteBatch.Draw(_sprite, _systemSpritePosition, Color.Red); // 绘制系统控制的精灵
            _spriteBatch.Draw(_sprite, _userSpritePosition, Color.White); // 绘制用户控制的精灵
            _spriteBatch.End();

            base.Update(gameTime);
        }
    }
}



2、通过 Rectangle 检测碰撞的 Demo(按键盘 O 键加载此 Demo)
Component/Collision/RectangleCollision.cs 

/*
 * 本 Demo 用于演示通过 Rectangle 类实现碰撞检测算法
 */

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;

namespace XNA.Component.Collision
{
    public class RectangleCollision : Microsoft.Xna.Framework.DrawableGameComponent
    {
        // 精灵绘制器
        SpriteBatch _spriteBatch;

        // 精灵对象
        Texture2D _sprite;

        // 精灵的位置(系统控制的)
        Vector2 _systemSpritePosition = new Vector2(600, 300);

        // 精灵的速度(系统控制的),单位:像素数/每帧
        int _systemSpriteSpeed = 6;

        // 精灵的位置(用户控制的)
        Vector2 _userSpritePosition = Vector2.Zero;

        // 精灵的速度(用户控制的),单位:像素数/每帧
        int _userSpriteSpeed = 6;

        // 是否发生了碰撞
        bool _collided = false;

        public RectangleCollision(Game game)
            : base(game)
        {

        }

        public override void Initialize()
        {
            base.Initialize();
        }

        protected override void LoadContent()
        {
            _spriteBatch = new SpriteBatch(Game.GraphicsDevice);
            _sprite = Game.Content.Load<Texture2D>("Image/Son");
        }

        public override void Update(GameTime gameTime)
        {
            // 如果系统控制的精灵和用户控制的精灵发生了碰撞,则停止动画
            if (!CheckCollision())
            {
                calcSystemSpritePosition();
                calcUserSpritePosition();
            }
            else
            {
                _collided = true;
            }

            base.Update(gameTime);
        }

        /// <summary>
        /// 检查系统控制的精灵和用户控制的精灵是否发生了碰撞(通过 Rectangle 类的帮助)
        /// </summary>
        /// <returns>两个精灵是否发生了碰撞</returns>
        private bool CheckCollision()
        {
            Rectangle systemSpriteRect = new Rectangle((int)_systemSpritePosition.X, (int)_systemSpritePosition.Y, _sprite.Width, _sprite.Height);
            Rectangle userSpriteRect = new Rectangle((int)_userSpritePosition.X, (int)_userSpritePosition.Y, _sprite.Width, _sprite.Height);

            if (systemSpriteRect.Intersects(userSpriteRect))
                return true;

            return false;
        }

        // 计算用户控制的精灵的位置
        private void calcUserSpritePosition()
        {
            KeyboardState keyboardState = Keyboard.GetState();

            if (keyboardState.IsKeyDown(Keys.Left) && _userSpritePosition.X >= 0)
                _userSpritePosition.X -= _userSpriteSpeed;
            if (keyboardState.IsKeyDown(Keys.Right) && _userSpritePosition.X <= Game.Window.ClientBounds.Width - _sprite.Width)
                _userSpritePosition.X += _userSpriteSpeed;
            if (keyboardState.IsKeyDown(Keys.Up) && _userSpritePosition.Y >= 0)
                _userSpritePosition.Y -= _userSpriteSpeed;
            if (keyboardState.IsKeyDown(Keys.Down) && _userSpritePosition.Y <= Game.Window.ClientBounds.Height - _sprite.Height)
                _userSpritePosition.Y += _userSpriteSpeed;

        }

        // 计算系统控制的精灵的位置
        private void calcSystemSpritePosition()
        {
            // 系统控制的精灵在 Y 轴方向上做往复运动
            _systemSpritePosition.Y += _systemSpriteSpeed;

            if (_systemSpritePosition.Y > Game.Window.ClientBounds.Height - _sprite.Height || _systemSpritePosition.Y < 0)
                _systemSpriteSpeed *= -1;
        }

        public override void Draw(GameTime gameTime)
        {
            if (_collided)
                Game.GraphicsDevice.Clear(Color.IndianRed);
            else
                Game.GraphicsDevice.Clear(Color.CornflowerBlue);

            // 在指定的位置上绘制精灵
            _spriteBatch.Begin();
            _spriteBatch.Draw(_sprite, _systemSpritePosition, Color.Red); // 绘制系统控制的精灵
            _spriteBatch.Draw(_sprite, _userSpritePosition, Color.White); // 绘制用户控制的精灵
            _spriteBatch.End();

            base.Update(gameTime);
        }
    }
}



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posted @ 2011-08-15 10:07  webabcd  阅读(4495)  评论(8编辑  收藏  举报