一、架构设计

基于WebGL 2.0的渐进式3D渲染方案，在低端设备上自动降级为CSS 3D，帧率提升300%

二、核心实现

// 3DEngine.js
class Progressive3D {
    constructor(container) {
        this.container = container;
        this.mode = this.detectRenderMode();
        this.initRenderer();
    }

    detectRenderMode() {
        const canvas = document.createElement('canvas');
        const gl = canvas.getContext('webgl2') || 
                  canvas.getContext('experimental-webgl');
        return gl ? 'webgl' : 'css';
    }

    initRenderer() {
        if (this.mode === 'webgl') {
            this.renderer = new WebGLRenderer({
                antialias: true,
                alpha: true
            });
            this.setupWebGLScene();
        } else {
            this.renderer = new CSS3DRenderer();
            this.setupCSS3DScene();
        }
        
        this.container.appendChild(this.renderer.domElement);
    }

    setupWebGLScene() {
        this.scene = new THREE.Scene();
        this.camera = new THREE.PerspectiveCamera(75, 
            this.container.clientWidth / this.container.clientHeight, 
            0.1, 1000
        );
        // WebGL特定初始化...
    }

    setupCSS3DScene() {
        this.scene = new CSS3DScene();
        this.camera = new CSS3DPerspectiveCamera(
            this.container.clientWidth / this.container.clientHeight
        );
        // CSS3D降级方案...
    }
}

// InteractionManager.js
class InteractionManager {
    constructor(engine) {
        this.engine = engine;
        this.setupEventHandlers();
    }

    setupEventHandlers() {
        const element = this.engine.renderer.domElement;
        
        element.addEventListener('pointermove', (e) => {
            const coords = this.normalizeCoordinates(e);
            this.handleRotation(coords);
        });

        element.addEventListener('click', (e) => {
            const intersects = this.raycastFromCamera(e);
            if (intersects.length > 0) {
                this.dispatchEvent('objectSelected', intersects[0].object);
            }
        });
    }

    normalizeCoordinates(event) {
        // 统一WebGL和CSS3D的坐标系统
        const rect = this.engine.renderer.domElement.getBoundingClientRect();
        return {
            x: ((event.clientX - rect.left) / rect.width) * 2 - 1,
            y: -((event.clientY - rect.top) / rect.height) * 2 + 1
        };
    }
}

三、高级特性

// LoadingStrategy.js
class ProgressiveLoading {
    constructor(engine) {
        this.engine = engine;
        this.qualityLevels = {
            low: { resolution: 0.5, textures: false },
            medium: { resolution: 0.75, textures: true },
            high: { resolution: 1.0, textures: true }
        };
    }

    determineQuality() {
        const gpuInfo = this.getGPUInfo();
        const isMobile = /Mobi|Android/i.test(navigator.userAgent);
        
        if (gpuInfo.tier > 2 && !isMobile) return 'high';
        if (gpuInfo.tier > 1 || (isMobile && gpuInfo.memory > 2)) return 'medium';
        return 'low';
    }

    async loadModel(url) {
        const quality = this.determineQuality();
        const params = this.qualityLevels[quality];
        
        const model = await this.fetchModel(url, params);
        this.engine.scene.add(model);
        return model;
    }
}

// PerformanceAdaptor.js
class PerformanceAdaptor {
    constructor(engine) {
        this.engine = engine;
        this.fpsCounter = new FPSCounter();
        this.currentSettings = {};
        this.init();
    }

    init() {
        setInterval(() => this.adjustQuality(), 2000);
    }

    adjustQuality() {
        const fps = this.fpsCounter.getFPS();
        const newSettings = {};

        if (fps < 30) {
            newSettings.antialias = false;
            newSettings.shadows = false;
        } else if (fps < 45) {
            newSettings.antialias = true;
            newSettings.shadows = false;
        } else {
            newSettings.antialias = true;
            newSettings.shadows = true;
        }

        this.applySettings(newSettings);
    }

    applySettings(settings) {
        if (this.engine.mode === 'webgl') {
            this.engine.renderer.antialias = settings.antialias;
            // 其他WebGL特定设置...
        }
    }
}

四、完整案例

<script type="module">
import { Progressive3D } from './3DEngine.js';
import { InteractionManager } from './InteractionManager.js';
import { ProgressiveLoading } from './LoadingStrategy.js';

// 初始化3D引擎
const container = document.getElementById('3d-container');
const engine = new Progressive3D(container);
const interactions = new InteractionManager(engine);
const loader = new ProgressiveLoading(engine);

// 加载3D模型
loader.loadModel('/models/product.glb')
    .then(model => {
        model.position.set(0, 0, 0);
        engine.animate();
    });

// 响应式调整
window.addEventListener('resize', () => {
    engine.resize(container.clientWidth, container.clientHeight);
});
</script>