three.js(20)-uv映射

作者: 姜治宇 | 来源:发表于2021-12-16 10:00 被阅读0次

three.js(20)-uv映射
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我们前面学习了三角面，知道一个立方体是由顶点（vectors）和索引（faces）坐标才可以画出来的。
uv是用来描述纹理位置的，也就是需要标注图片四个顶点的位置。不过这个位置坐标比较特殊，值必须是在0~1之间的。请看下图：

bear.png

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <script src="http://www.yanhuangxueyuan.com/versions/threejsR92/build/three.js"></script>
    <script src="http://www.yanhuangxueyuan.com/threejs/examples/js/controls/OrbitControls.js"></script>
    <title>Document</title>
</head>

<body>
    <div id="webgl"></div>
</body>

</html>
<script>
    var scene = new THREE.Scene();
    //添加坐标轴
    var axes = new THREE.AxesHelper(300);//50表示xyz轴的长度，红:x,绿:y,蓝:z
    scene.add(axes);
  
    var geometry = new THREE.BufferGeometry();
    console.log(geometry);
    var points = new Float32Array([
        -5, 5, 5,
        5, 5, 5,
        5, 5, -5,
        -5, 5, -5
    ]);
    var index = [
        0,1,2,
        2,3,0
    ];
    var uv =new Float32Array([
      0,0,
      1,0,
      1,1,
      0,1  
    ]);
    geometry.addAttribute('position', new THREE.BufferAttribute(points, 3));
    geometry.setIndex(index); 
    geometry.addAttribute('uv',new THREE.BufferAttribute(uv,2));
    const textureLoader = new THREE.TextureLoader();
    const textureUrl = 'https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fpic.jj20.com%2Fup%2Fallimg%2F512%2F040912153611%2F120409153611-11.jpg&refer=http%3A%2F%2Fpic.jj20.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=jpeg?sec=1642141424&t=949616f6854cb89898a29553af2e53ff';
    var material = new THREE.MeshBasicMaterial({
        map: textureLoader.load(textureUrl)
    }); //材质对象Material
    
    var mesh = new THREE.Mesh(geometry, material); //网格模型对象Mesh
    scene.add(mesh);

    //创建相机对象
    var camera = new THREE.PerspectiveCamera(45, 2, 0.1, 2000);
    camera.position.set(20, 20, 20); //设置相机位置
    camera.lookAt(new THREE.Vector3(0, 0, 0)); //设置相机方向(指向的场景对象)


    /**
     * 创建渲染器对象
     */
    var renderer = new THREE.WebGLRenderer({
        antialias: true //消除锯齿
    });
    renderer.setSize(1000, 500);//设置渲染区域尺寸
    renderer.setClearColor(0xb9d3ff, 1); //设置背景颜色
    renderer.render(scene, camera);//渲染必须有场景和相机两个对象

    var cont = document.getElementById('webgl');
    cont.appendChild(renderer.domElement);

    //增加鼠标拾取效果
    var controls = new THREE.OrbitControls(camera, renderer.domElement);
    controls.addEventListener('change', () => {
        renderer.render(scene, camera);
    });
</script>

img.gif