JavaScript系列（49）--游戏引擎实现详解

JavaScript游戏引擎实现详解 🎮

今天，让我们深入探讨JavaScript的游戏引擎实现。游戏引擎是一个复杂的系统，它需要处理渲染、物理、音频、输入等多个方面，让我们一步步实现一个基础但功能完整的游戏引擎。

游戏引擎基础概念 🌟

💡 小知识：游戏引擎是一个为游戏开发提供核心功能的框架，它通常包括渲染系统、物理引擎、音频系统、输入处理、资源管理等模块。通过合理的架构设计，这些模块可以协同工作，为游戏开发提供强大的支持。

基本实现 📊

// 1. 游戏引擎核心
class GameEngine {
    constructor(canvas) {
        this.canvas = canvas;
        this.context = canvas.getContext('2d');
        
        // 核心系统
        this.renderer = new Renderer(this.context);
        this.physics = new PhysicsSystem();
        this.input = new InputManager();
        this.audio = new AudioSystem();
        
        // 游戏状态
        this.scenes = new Map();
        this.currentScene = null;
        this.isRunning = false;
        
        // 时间管理
        this.lastTime = 0;
        this.deltaTime = 0;
    }
    
    // 初始化引擎
    init() {
        this.input.init();
        this.audio.init();
        window.requestAnimationFrame(this.gameLoop.bind(this));
    }
    
    // 游戏主循环
    gameLoop(timestamp) {
        // 计算时间增量
        this.deltaTime = (timestamp - this.lastTime) / 1000;
        this.lastTime = timestamp;
        
        if (this.isRunning && this.currentScene) {
            this.update();
            this.render();
        }
        
        window.requestAnimationFrame(this.gameLoop.bind(this));
    }
    
    // 更新游戏状态
    update() {
        this.physics.update(this.deltaTime);
        this.currentScene.update(this.deltaTime);
        this.input.update();
    }
    
    // 渲染游戏画面
    render() {
        this.context.clearRect(
            0, 0,
            this.canvas.width,
            this.canvas.height
        );
        this.currentScene.render(this.renderer);
    }
    
    // 场景管理
    addScene(name, scene) {
        this.scenes.set(name, scene);
    }
    
    loadScene(name) {
        const scene = this.scenes.get(name);
        if (scene) {
            if (this.currentScene) {
                this.currentScene.onExit();
            }
            this.currentScene = scene;
            scene.onEnter();
        }
    }
}

// 2. 渲染系统
class Renderer {
    constructor(context) {
        this.context = context;
        this.camera = new Camera();
    }
    
    // 绘制精灵
    drawSprite(sprite) {
        const { position, scale, rotation } = sprite.transform;
        const { texture, width, height } = sprite;
        
        this.context.save();
        
        // 应用相机变换
        this.context.translate(
            -this.camera.position.x,
            -this.camera.position.y
        );
        
        // 应用精灵变换
        this.context.translate(position.x, position.y);
        this.context.rotate(rotation);
        this.context.scale(scale.x, scale.y);
        
        // 绘制精灵
        this.context.drawImage(
            texture,
            -width / 2,
            -height / 2,
            width,
            height
        );
        
        this.context.restore();
    }
    
    // 绘制图元
    drawPrimitive(primitive) {
        this.context.save();
        
        this.context.fillStyle = primitive.color;
        this.context.beginPath();
        
        switch (primitive.type) {
            case 'rectangle':
                this.context.fillRect(
                    primitive.x,
                    primitive.y,
                    primitive.width,
                    primitive.height
                );
                break;
            case 'circle':
                this.context.arc(
                    primitive.x,
                    primitive.y,
                    primitive.radius,
                    0,
                    Math.PI * 2
                );
                this.context.fill();
                break;
        }
        
        this.context.restore();
    }
}

// 3. 物理系统
class PhysicsSystem {
    constructor() {
        this.bodies = [];
        this.gravity = new Vector2(0, 9.81);
    }
    
    addBody(body) {
        this.bodies.push(body);
    }
    
    removeBody(body) {
        const index = this.bodies.indexOf(body);
        if (index !== -1) {
            this.bodies.splice(index, 1);
        }
    }
    
    update(deltaTime) {
        // 更新物理体
        for (const body of this.bodies) {
            if (!body.isStatic) {
                // 应用重力
                body.velocity.add(
                    Vector2.multiply(this.gravity, deltaTime)
                );
                
                // 更新位置
                body.position.add(
                    Vector2.multiply(body.velocity, deltaTime)
                );
            }
        }
        
        // 碰撞检测和处理
        this.detectCollisions();
    }
    
    detectCollisions() {
        for (let i = 0; i < this.bodies.length; i++) {
            for (let j = i + 1; j < this.bodies.length; j++) {
                const bodyA = this.bodies[i];
                const bodyB = this.bodies[j];
                
                if (this.checkCollision(bodyA, bodyB)) {
                    this.resolveCollision(bodyA, bodyB);
                }
            }
        }
    }
}

高级功能实现 🚀

// 1. 实体组件系统
class Entity {
    constructor() {
        this.components = new Map();
        this.id = Entity.nextId++;
    }
    
    addComponent(component) {
        component.entity = this;
        this.components.set(component.constructor, component);
    }
    
    getComponent(componentClass) {
        return this.components.get(componentClass);
    }
    
    removeComponent(componentClass) {
        const component = this.components.get(componentClass);
        if (component) {
            component.entity = null;
            this.components.delete(componentClass);
        }
    }
    
    update(deltaTime) {
        for (const component of this.components.values()) {
            if (component.update) {
                component.update(deltaTime);
            }
        }
    }
}

// 2. 组件系统
class Component {
    constructor() {
        this.entity = null;
    }
    
    // 生命周期方法
    onAdd() {}
    onRemove() {}
    update(deltaTime) {}
}

class TransformComponent extends Component {
    constructor() {
        super();
        this.position = new Vector2();
        this.rotation = 0;
        this.scale = new Vector2(1, 1);
    }
}

class SpriteComponent extends Component {
    constructor(texture) {
        super();
        this.texture = texture;
        this.width = texture.width;
        this.height = texture.height;
    }
    
    render(renderer) {
        const transform = this.entity.getComponent(TransformComponent);
        if (transform) {
            renderer.drawSprite({
                texture: this.texture,
                width: this.width,
                height: this.height,
                transform
            });
        }
    }
}

// 3. 场景管理
class Scene {
    constructor() {
        this.entities = new Set();
        this.systems = new Map();
    }
    
    addEntity(entity) {
        this.entities.add(entity);
    }
    
    removeEntity(entity) {
        this.entities.delete(entity);
    }
    
    addSystem(system) {
        system.scene = this;
        this.systems.set(system.constructor, system);
    }
    
    update(deltaTime) {
        // 更新所有系统
        for (const system of this.systems.values()) {
            system.update(deltaTime);
        }
        
        // 更新所有实体
        for (const entity of this.entities) {
            entity.update(deltaTime);
        }
    }
    
    render(renderer) {
        for (const entity of this.entities) {
            const sprite = entity.getComponent(SpriteComponent);
            if (sprite) {
                sprite.render(renderer);
            }
        }
    }
    
    // 场景生命周期
    onEnter() {}
    onExit() {}
}

实际应用场景 💼

// 1. 游戏对象实现
class GameObject extends Entity {
    constructor(x = 0, y = 0) {
        super();
        
        // 添加基本组件
        const transform = new TransformComponent();
        transform.position.set(x, y);
        this.addComponent(transform);
    }
    
    // 便捷方法
    setPosition(x, y) {
        const transform = this.getComponent(TransformComponent);
        transform.position.set(x, y);
    }
    
    setRotation(angle) {
        const transform = this.getComponent(TransformComponent);
        transform.rotation = angle;
    }
    
    setScale(x, y) {
        const transform = this.getComponent(TransformComponent);
        transform.scale.set(x, y);
    }
}

// 2. 游戏角色实现
class Player extends GameObject {
    constructor(x, y) {
        super(x, y);
        
        // 添加精灵组件
        const sprite = new SpriteComponent(
            ResourceManager.getTexture('player')
        );
        this.addComponent(sprite);
        
        // 添加物理组件
        const physics = new PhysicsComponent();
        physics.mass = 1;
        physics.friction = 0.1;
        this.addComponent(physics);
        
        // 添加输入组件
        const input = new InputComponent();
        input.bindKey('ArrowLeft', this.moveLeft.bind(this));
        input.bindKey('ArrowRight', this.moveRight.bind(this));
        input.bindKey('Space', this.jump.bind(this));
        this.addComponent(input);
    }
    
    moveLeft() {
        const physics = this.getComponent(PhysicsComponent);
        physics.applyForce(new Vector2(-100, 0));
    }
    
    moveRight() {
        const physics = this.getComponent(PhysicsComponent);
        physics.applyForce(new Vector2(100, 0));
    }
    
    jump() {
        const physics = this.getComponent(PhysicsComponent);
        if (physics.isGrounded) {
            physics.applyImpulse(new Vector2(0, -200));
        }
    }
}

// 3. 游戏关卡实现
class GameLevel extends Scene {
    constructor() {
        super();
        
        // 创建玩家
        const player = new Player(100, 100);
        this.addEntity(player);
        
        // 创建平台
        this.createPlatform(0, 500, 800, 20);
        this.createPlatform(300, 400, 200, 20);
        this.createPlatform(100, 300, 200, 20);
        
        // 添加系统
        this.addSystem(new PhysicsSystem());
        this.addSystem(new CollisionSystem());
        this.addSystem(new RenderSystem());
    }
    
    createPlatform(x, y, width, height) {
        const platform = new GameObject(x, y);
        
        const sprite = new SpriteComponent(
            ResourceManager.getTexture('platform')
        );
        sprite.width = width;
        sprite.height = height;
        platform.addComponent(sprite);
        
        const physics = new PhysicsComponent();
        physics.isStatic = true;
        physics.setBox(width, height);
        platform.addComponent(physics);
        
        this.addEntity(platform);
    }
}

性能优化技巧 ⚡

// 1. 对象池系统
class ObjectPool {
    constructor(factory, initialSize = 10) {
        this.factory = factory;
        this.activeObjects = new Set();
        this.inactiveObjects = [];
        
        // 预创建对象
        for (let i = 0; i < initialSize; i++) {
            this.inactiveObjects.push(this.factory());
        }
    }
    
    spawn(x, y) {
        let object;
        
        if (this.inactiveObjects.length > 0) {
            object = this.inactiveObjects.pop();
        } else {
            object = this.factory();
        }
        
        object.setPosition(x, y);
        this.activeObjects.add(object);
        return object;
    }
    
    despawn(object) {
        if (this.activeObjects.has(object)) {
            this.activeObjects.delete(object);
            this.inactiveObjects.push(object);
        }
    }
    
    update(deltaTime) {
        for (const object of this.activeObjects) {
            object.update(deltaTime);
        }
    }
}

// 2. 四叉树空间分区
class QuadTree {
    constructor(bounds, maxObjects = 10, maxLevels = 4, level = 0) {
        this.bounds = bounds;
        this.maxObjects = maxObjects;
        this.maxLevels = maxLevels;
        this.level = level;
        this.objects = [];
        this.nodes = [];
    }
    
    clear() {
        this.objects = [];
        
        for (let i = 0; i < this.nodes.length; i++) {
            if (this.nodes[i]) {
                this.nodes[i].clear();
                this.nodes[i] = null;
            }
        }
    }
    
    split() {
        const subWidth = this.bounds.width / 2;
        const subHeight = this.bounds.height / 2;
        const x = this.bounds.x;
        const y = this.bounds.y;
        
        this.nodes[0] = new QuadTree({
            x: x + subWidth,
            y: y,
            width: subWidth,
            height: subHeight
        }, this.maxObjects, this.maxLevels, this.level + 1);
        
        this.nodes[1] = new QuadTree({
            x: x,
            y: y,
            width: subWidth,
            height: subHeight
        }, this.maxObjects, this.maxLevels, this.level + 1);
        
        this.nodes[2] = new QuadTree({
            x: x,
            y: y + subHeight,
            width: subWidth,
            height: subHeight
        }, this.maxObjects, this.maxLevels, this.level + 1);
        
        this.nodes[3] = new QuadTree({
            x: x + subWidth,
            y: y + subHeight,
            width: subWidth,
            height: subHeight
        }, this.maxObjects, this.maxLevels, this.level + 1);
    }
    
    getIndex(rect) {
        const verticalMidpoint = this.bounds.x + (this.bounds.width / 2);
        const horizontalMidpoint = this.bounds.y + (this.bounds.height / 2);
        
        const topQuadrant = (rect.y < horizontalMidpoint && 
                            rect.y + rect.height < horizontalMidpoint);
        const bottomQuadrant = (rect.y > horizontalMidpoint);
        
        if (rect.x < verticalMidpoint && 
            rect.x + rect.width < verticalMidpoint) {
            if (topQuadrant) {
                return 1;
            } else if (bottomQuadrant) {
                return 2;
            }
        } else if (rect.x > verticalMidpoint) {
            if (topQuadrant) {
                return 0;
            } else if (bottomQuadrant) {
                return 3;
            }
        }
        
        return -1;
    }
}

// 3. 渲染优化
class RenderOptimizer {
    constructor(renderer) {
        this.renderer = renderer;
        this.visibleObjects = new Set();
        this.frustum = new Frustum();
    }
    
    updateVisibility(camera, objects) {
        this.visibleObjects.clear();
        this.frustum.updateFromCamera(camera);
        
        for (const object of objects) {
            if (this.frustum.intersectsBox(object.getBoundingBox())) {
                this.visibleObjects.add(object);
            }
        }
    }
    
    render() {
        // 按材质排序
        const sortedObjects = Array.from(this.visibleObjects)
            .sort((a, b) => a.material.id - b.material.id);
        
        // 批量渲染
        let currentMaterial = null;
        for (const object of sortedObjects) {
            if (object.material !== currentMaterial) {
                currentMaterial = object.material;
                this.renderer.setMaterial(currentMaterial);
            }
            this.renderer.renderObject(object);
        }
    }
}

最佳实践建议 💡

游戏引擎架构设计

// 1. 模块化设计
class GameModule {
    constructor(engine) {
        this.engine = engine;
    }
    
    init() {}
    update(deltaTime) {}
    destroy() {}
}

// 2. 事件系统
class EventSystem extends GameModule {
    constructor(engine) {
        super(engine);
        this.listeners = new Map();
    }
    
    on(event, callback) {
        if (!this.listeners.has(event)) {
            this.listeners.set(event, new Set());
        }
        this.listeners.get(event).add(callback);
    }
    
    off(event, callback) {
        const callbacks = this.listeners.get(event);
        if (callbacks) {
            callbacks.delete(callback);
        }
    }
    
    emit(event, data) {
        const callbacks = this.listeners.get(event);
        if (callbacks) {
            for (const callback of callbacks) {
                callback(data);
            }
        }
    }
}

// 3. 资源管理
class ResourceManager extends GameModule {
    constructor(engine) {
        super(engine);
        this.resources = new Map();
        this.loading = new Map();
    }
    
    async load(url, type) {
        if (this.resources.has(url)) {
            return this.resources.get(url);
        }
        
        if (this.loading.has(url)) {
            return this.loading.get(url);
        }
        
        const loadPromise = this.loadResource(url, type);
        this.loading.set(url, loadPromise);
        
        try {
            const resource = await loadPromise;
            this.resources.set(url, resource);
            this.loading.delete(url);
            return resource;
        } catch (error) {
            this.loading.delete(url);
            throw error;
        }
    }
    
    async loadResource(url, type) {
        switch (type) {
            case 'image':
                return this.loadImage(url);
            case 'audio':
                return this.loadAudio(url);
            case 'json':
                return this.loadJSON(url);
            default:
                throw new Error(`Unsupported resource type: ${type}`);
        }
    }
}