three.js 06-05 之从 SVG 拉伸创建物体
方昊
本篇我们来探讨一下在 three.js 中如何从 SVG 拉伸一个图形来创建物体。首先，我们从 https://github.com/asutherland/d3-threeD 获取一个叫 d3-threeD 的小型库，它可以将 SVG 路径转换成 three.js 图形。
下面来看看利用 THREE.ExtrudeGeometry 如何将一个蝙蝠标识符的 SVG 图案转成三维图形，核心代码如下所示：
<!-- SVG 标签 -->
<svg version="1.0" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" width="1152px" height="1152px" xml:space="preserve">
<g>
<path id="batman-path" style="fill:rgb(0,0,0);" d="M 261.135 114.535 C 254.906 116.662 247.491 118.825 244.659 119.344 C 229.433 122.131 177.907 142.565 151.973 156.101 C 111.417 177.269 78.9808 203.399 49.2992 238.815 C 41.0479 248.66 26.5057 277.248 21.0148 294.418 C 14.873 313.624 15.3588 357.341 21.9304 376.806 C 29.244 398.469 39.6107 416.935 52.0865 430.524 C 58.2431 437.23 63.3085 443.321 63.3431 444.06 C 63.4748 446.883 102.278 479.707 120.51 492.418 C 131.003 499.734 148.168 509.93 158.654 515.075 C 169.139 520.22 179.431 525.34 181.524 526.454 C 187.725 529.754 187.304 527.547 179.472 515.713 C 164.806 493.553 158.448 464.659 164.322 446.861 C 169.457 431.303 192.013 421.501 214.324 425.132 C 234.042 428.341 252.142 439.186 270.958 459.064 C 286.677 475.67 292.133 482.967 295.31 491.634 C 297.466 497.514 298.948 495.91 304.862 481.293 C 313.673 459.519 329.808 445.735 346.35 445.851 C 367.654 446 399.679 478.239 412.801 512.745 C 414.093 516.144 416.593 522.632 418.355 527.163 C 420.118 531.695 423.604 542.319 426.103 550.773 C 430.848 566.832 432.355 566.851 434.872 550.88 C 436.395 541.215 451.403 502.522 455.655 497.298 C 457.038 495.599 460.63 489.896 463.636 484.625 C 471.696 470.498 492.318 452.688 505.387 448.568 C 514.602 445.663 517.533 445.549 525.51 447.782 C 539.676 451.749 553.43 467.773 560.706 488.788 L 563.242 496.114 L 567.096 490.012 C 577.709 473.208 593.665 453.899 602.47 447.206 C 607.884 443.09 613.378 438.825 614.679 437.729 C 615.98 436.632 622.927 433.259 630.118 430.233 C 655.159 419.693 681.195 423.407 693.273 439.241 C 697.957 445.382 698.932 448.971 699.538 462.294 C 700.174 476.284 699.51 479.864 693.686 493.854 C 690.073 502.533 684.912 512.883 682.217 516.854 C 679.523 520.825 678.172 524.074 679.215 524.074 C 681.932 524.074 718.787 504.481 732.525 495.734 C 760.018 478.228 788.909 452.599 803.9 432.418 C 807.266 427.886 810.569 423.715 811.239 423.149 C 814.498 420.395 828.253 393.099 833.17 379.627 C 838.223 365.782 838.713 361.822 838.741 334.582 C 838.776 300.425 836.431 291.124 820.154 260.873 C 810.649 243.207 807.498 239.005 788.417 218.543 C 751.511 178.968 688.147 142.549 621.582 122.654 C 581.7 110.734 580.388 110.465 580.388 114.195 C 580.388 115.328 581.302 116.255 582.418 116.255 C 584.279 116.255 587.705 122.106 603.399 152.085 C 613.977 172.29 618.077 189.427 618.264 214.21 C 618.42 234.928 617.88 238.368 612.285 252.269 C 604.327 272.04 590.066 286.889 572.829 293.352 C 558.526 298.714 549.193 297.86 535.704 289.955 C 526.777 284.723 512.304 267.644 509.816 259.404 C 509.132 257.138 507.129 251.358 505.366 246.558 C 503.602 241.759 501.646 231.564 501.018 223.902 C 500.39 216.24 498.491 198.402 496.797 184.261 C 495.104 170.121 493.307 152.047 492.803 144.097 C 492.299 136.147 491.292 125.625 490.565 120.715 L 489.242 111.787 L 483.323 118.267 C 480.067 121.832 477.404 125.618 477.404 126.681 C 477.404 127.744 476.603 128.613 475.624 128.613 C 474.645 128.613 471.275 132.321 468.135 136.852 L 462.426 145.091 L 431.038 145.091 L 399.65 145.091 L 386.811 128.494 C 379.749 119.365 373.509 112.36 372.943 112.926 C 372.377 113.491 371.57 118.875 371.15 124.888 C 370.73 130.902 368.94 147.744 367.172 162.315 C 365.405 176.887 363.523 195.424 362.99 203.509 C 360.283 244.622 352.784 266.044 335.323 282.544 C 326.456 290.923 312.488 297.497 303.508 297.518 C 294.864 297.539 278.732 290.063 269.473 281.748 C 246.952 261.521 238.846 229.614 245.481 187.314 C 247.894 171.928 266.562 131.612 275.927 121.56 C 277.987 119.348 279.673 116.786 279.673 115.867 C 279.673 114.947 279.905 113.593 280.188 112.856 C 281.28 110.017 271.977 110.837 261.136 114.536 L 261.135 114.535 "/>
</g>
</svg>幸运的是我们不必自己写代码来解析类似的指令，使用 d3-threeD 库，可以自动转换这些指令。该库原是跟优秀的 D3.js 库一同开发使用的，但是 d3-threeD 库在此基础上做了一些小调整，以便我们能够单独使用其中的部分功能。
下面的代码展示了如何加载前面看到的 SVG，并转换成 THREE.ExtrudeGeometry 并显示在 three.js 场景中：
// 获取 path 标签 d 属性中的数据
var svgString = $("#batman-path").attr("d");
// 定义 svg
var svgShape = transformSVGPathExposed(svgString);
var options = {
amount: 10,
bevelThinkness: 2,
bevelSize: 1,
bevelSegments: 3,
bevelEnabled: true,
curveSegments: 12,
steps: 1
};
var svgGeometry = new THREE.ExtrudeGeometry(svgShape, options);
var svgMaterial = new THREE.MeshPhongMaterial({color: 0x333333, shininess: 100});
var svg = new THREE.Mesh(svgGeometry, svgMaterial);
下面我们给出完整的示例代码：
<!DOCTYPE html>
<html>
<head>
<title>示例 06.05 - SvgGeometry</title>
<script src="../build/three.js"></script>
<script src="../build/js/controls/OrbitControls.js"></script>
<script src="../build/js/libs/stats.min.js"></script>
<script src="../build/js/libs/dat.gui.min.js"></script>
<script src="../jquery/jquery-3.2.1.min.js"></script>
<script src="../build/js/libs/d3-threeD.js"></script>
<style>
body {
/* 设置 margin 为 0，并且 overflow 为 hidden，来完成页面样式 */
margin: 0;
overflow: hidden;
}
/* 统计对象的样式 */
#Stats-output {
position: absolute;
left: 0px;
top: 0px;
}
</style>
</head>
<body>
<!-- 用于 WebGL 输出的 Div -->
<div id="webgl-output"></div>
<!-- 用于统计 FPS 输出的 Div -->
<div id="stats-output"></div>
<!-- SVG 标签 -->
<svg version="1.0" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" width="1152px" height="1152px" xml:space="preserve">
<g>
<path id="batman-path" style="fill:rgb(0,0,0);" d="M 261.135 114.535 C 254.906 116.662 247.491 118.825 244.659 119.344 C 229.433 122.131 177.907 142.565 151.973 156.101 C 111.417 177.269 78.9808 203.399 49.2992 238.815 C 41.0479 248.66 26.5057 277.248 21.0148 294.418 C 14.873 313.624 15.3588 357.341 21.9304 376.806 C 29.244 398.469 39.6107 416.935 52.0865 430.524 C 58.2431 437.23 63.3085 443.321 63.3431 444.06 C 63.4748 446.883 102.278 479.707 120.51 492.418 C 131.003 499.734 148.168 509.93 158.654 515.075 C 169.139 520.22 179.431 525.34 181.524 526.454 C 187.725 529.754 187.304 527.547 179.472 515.713 C 164.806 493.553 158.448 464.659 164.322 446.861 C 169.457 431.303 192.013 421.501 214.324 425.132 C 234.042 428.341 252.142 439.186 270.958 459.064 C 286.677 475.67 292.133 482.967 295.31 491.634 C 297.466 497.514 298.948 495.91 304.862 481.293 C 313.673 459.519 329.808 445.735 346.35 445.851 C 367.654 446 399.679 478.239 412.801 512.745 C 414.093 516.144 416.593 522.632 418.355 527.163 C 420.118 531.695 423.604 542.319 426.103 550.773 C 430.848 566.832 432.355 566.851 434.872 550.88 C 436.395 541.215 451.403 502.522 455.655 497.298 C 457.038 495.599 460.63 489.896 463.636 484.625 C 471.696 470.498 492.318 452.688 505.387 448.568 C 514.602 445.663 517.533 445.549 525.51 447.782 C 539.676 451.749 553.43 467.773 560.706 488.788 L 563.242 496.114 L 567.096 490.012 C 577.709 473.208 593.665 453.899 602.47 447.206 C 607.884 443.09 613.378 438.825 614.679 437.729 C 615.98 436.632 622.927 433.259 630.118 430.233 C 655.159 419.693 681.195 423.407 693.273 439.241 C 697.957 445.382 698.932 448.971 699.538 462.294 C 700.174 476.284 699.51 479.864 693.686 493.854 C 690.073 502.533 684.912 512.883 682.217 516.854 C 679.523 520.825 678.172 524.074 679.215 524.074 C 681.932 524.074 718.787 504.481 732.525 495.734 C 760.018 478.228 788.909 452.599 803.9 432.418 C 807.266 427.886 810.569 423.715 811.239 423.149 C 814.498 420.395 828.253 393.099 833.17 379.627 C 838.223 365.782 838.713 361.822 838.741 334.582 C 838.776 300.425 836.431 291.124 820.154 260.873 C 810.649 243.207 807.498 239.005 788.417 218.543 C 751.511 178.968 688.147 142.549 621.582 122.654 C 581.7 110.734 580.388 110.465 580.388 114.195 C 580.388 115.328 581.302 116.255 582.418 116.255 C 584.279 116.255 587.705 122.106 603.399 152.085 C 613.977 172.29 618.077 189.427 618.264 214.21 C 618.42 234.928 617.88 238.368 612.285 252.269 C 604.327 272.04 590.066 286.889 572.829 293.352 C 558.526 298.714 549.193 297.86 535.704 289.955 C 526.777 284.723 512.304 267.644 509.816 259.404 C 509.132 257.138 507.129 251.358 505.366 246.558 C 503.602 241.759 501.646 231.564 501.018 223.902 C 500.39 216.24 498.491 198.402 496.797 184.261 C 495.104 170.121 493.307 152.047 492.803 144.097 C 492.299 136.147 491.292 125.625 490.565 120.715 L 489.242 111.787 L 483.323 118.267 C 480.067 121.832 477.404 125.618 477.404 126.681 C 477.404 127.744 476.603 128.613 475.624 128.613 C 474.645 128.613 471.275 132.321 468.135 136.852 L 462.426 145.091 L 431.038 145.091 L 399.65 145.091 L 386.811 128.494 C 379.749 119.365 373.509 112.36 372.943 112.926 C 372.377 113.491 371.57 118.875 371.15 124.888 C 370.73 130.902 368.94 147.744 367.172 162.315 C 365.405 176.887 363.523 195.424 362.99 203.509 C 360.283 244.622 352.784 266.044 335.323 282.544 C 326.456 290.923 312.488 297.497 303.508 297.518 C 294.864 297.539 278.732 290.063 269.473 281.748 C 246.952 261.521 238.846 229.614 245.481 187.314 C 247.894 171.928 266.562 131.612 275.927 121.56 C 277.987 119.348 279.673 116.786 279.673 115.867 C 279.673 114.947 279.905 113.593 280.188 112.856 C 281.28 110.017 271.977 110.837 261.136 114.536 L 261.135 114.535 "/>
</g>
</svg>
<!-- 运行 Three.js 示例的 Javascript 代码 -->
<script type="text/javascript">
var scene;
var camera;
var render;
var webglRender;
//var canvasRender;
var controls;
var stats;
var guiParams;
var ground;
var svg;
var meshMaterial;
var ambientLight;
var spotLight;
var axesHelper;
//var cameraHelper;
$(function() {
stats = initStats();
scene = new THREE.Scene();
webglRender = new THREE.WebGLRenderer( {antialias: true, alpha: true} ); // antialias 抗锯齿
webglRender.setSize(window.innerWidth, window.innerHeight);
webglRender.setClearColor(0xeeeeee, 1.0);
webglRender.shadowMap.enabled = true; // 允许阴影投射
render = webglRender;
camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 0.01, 1000); // 2147483647
camera.position.set(-45.5, 68.2, 90.9);
var target = new THREE.Vector3(10, 0 , 0);
controls = new THREE.OrbitControls(camera, render.domElement);
controls.target = target;
camera.lookAt(target);
$('#webgl-output')[0].appendChild(render.domElement);
window.addEventListener('resize', onWindowResize, false);
// 加入一个坐标轴：X（橙色）、Y（绿色）、Z（蓝色）
axesHelper = new THREE.AxesHelper(60);
scene.add(axesHelper);
ambientLight = new THREE.AmbientLight(0x0c0c0c);
scene.add(ambientLight);
spotLight = new THREE.SpotLight(0xffffff);
spotLight.position.set(0, 60, 30);
spotLight.shadow.mapSize.width = 5120; // 必须是 2的幂，默认值为 512
spotLight.shadow.mapSize.height = 5120; // 必须是 2的幂，默认值为 512
spotLight.castShadow = true;
scene.add(spotLight);
//cameraHelper = new THREE.CameraHelper(spotLight.shadow.camera);
//scene.add(cameraHelper);
// 加入一个地面
var groundGeometry = new THREE.PlaneGeometry(100, 100, 4, 4);
var groundMaterial = new THREE.MeshLambertMaterial({color: 0x777777}); // MeshBasicMaterial 材质不能接收阴影
ground = new THREE.Mesh(groundGeometry, groundMaterial);
ground.rotation.set(-0.5 * Math.PI, 0, 0); // 沿着 X轴旋转-90°
ground.receiveShadow = true;
scene.add(ground);
// 材质
meshMaterial = [
new THREE.MeshNormalMaterial({side: THREE.DoubleSide}),
new THREE.MeshBasicMaterial({wireframe: true})
];
// 获取 path 标签 d 属性中的数据
var svgString = $("#batman-path").attr("d");
/** 用来保存那些需要修改的变量 */
guiParams = new function() {
this.rotationSpeed = 0.02;
this.options = {
amount: 10,
bevelThinkness: 2,
bevelSize: 1,
bevelSegments: 3,
bevelEnabled: true,
curveSegments: 12,
steps: 1
};
}
/** 定义 dat.GUI 对象，并绑定 guiParams 的几个属性 */
var gui = new dat.GUI();
gui.add(guiParams.options, "amount", 0, 20).onChange(function(e){updateMesh(svgString)});
gui.add(guiParams.options, "bevelThinkness", 0, 10).onChange(function(e){updateMesh(svgString)});
gui.add(guiParams.options, "bevelSize", 0, 10).onChange(function(e){updateMesh(svgString)});
gui.add(guiParams.options, "bevelSegments", 0, 30, 1).onChange(function(e){updateMesh(svgString)});
gui.add(guiParams.options, "bevelEnabled").onChange(function(e){updateMesh(svgString)});
gui.add(guiParams.options, "curveSegments", 1, 30, 1).onChange(function(e){updateMesh(svgString)});
gui.add(guiParams.options, "steps", 1, 5, 1).onChange(function(e){updateMesh(svgString)});
updateMesh(svgString);
renderScene();
});
/** 渲染场景 */
function renderScene() {
stats.update();
rotateMesh(); // 旋转物体
requestAnimationFrame(renderScene);
render.render(scene, camera);
}
/** 初始化 stats 统计对象 */
function initStats() {
stats = new Stats();
stats.setMode(0); // 0 为监测 FPS；1 为监测渲染时间
$('#stats-output').append(stats.domElement);
return stats;
}
/** 当浏览器窗口大小变化时触发 */
function onWindowResize() {
camera.aspect = window.innerWidth / window.innerHeight;
camera.updateProjectionMatrix();
render.setSize(window.innerWidth, window.innerHeight);
}
/** 旋转物体 */
var step = 0;
function rotateMesh() {
step += guiParams.rotationSpeed;
scene.traverse(function(mesh) {
if (mesh === svg) {
//mesh.rotation.x = step;
mesh.rotation.y = step;
//mesh.rotation.z = step;
}
});
}
function updateMesh(svgString) {
scene.remove(svg);
// 定义 svg
var svgShape = transformSVGPathExposed(svgString);
var svgGeometry = new THREE.ExtrudeGeometry(svgShape, guiParams.options);
var svgMaterial = new THREE.MeshPhongMaterial({color: 0x333333, shininess: 100});
svg = new THREE.Mesh(svgGeometry, svgMaterial);
svg.scale.x = 0.05;
svg.scale.y = 0.05;
svg.scale.z = 0.2;
scene.add(svg);
}
</script>
</body>
</html>未完待续···
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