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@@ -1,47 +1,607 @@
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-<!DOCTYPE html><html lang="zh"><head>
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- <meta charset="utf-8">
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- <title>Indexed Textures for Picking and Color</title>
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- <meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
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- <meta name="twitter:card" content="summary_large_image">
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- <meta name="twitter:site" content="@threejs">
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- <meta name="twitter:title" content="Three.js – Indexed Textures for Picking and Color">
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- <meta property="og:image" content="https://threejs.org/files/share.png">
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- <link rel="shortcut icon" href="/files/favicon_white.ico" media="(prefers-color-scheme: dark)">
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- <link rel="shortcut icon" href="/files/favicon.ico" media="(prefers-color-scheme: light)">
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-
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- <link rel="stylesheet" href="/manual/resources/lesson.css">
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- <link rel="stylesheet" href="/manual/resources/lang.css">
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-<!-- Import maps polyfill -->
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-<!-- Remove this when import maps will be widely supported -->
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-<script async src="https://unpkg.com/[email protected]/dist/es-module-shims.js"></script>
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-
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-<script type="importmap">
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+<!DOCTYPE html>
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+<html lang="zh">
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+
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+<head>
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+ <meta charset="utf-8">
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+ <title>使用纹理索引来拾取和着色</title>
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+ <meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
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+ <meta name="twitter:card" content="summary_large_image">
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+ <meta name="twitter:site" content="@threejs">
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+ <meta name="twitter:title" content="Three.js – Indexed Textures for Picking and Color">
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+ <meta property="og:image" content="https://threejs.org/files/share.png">
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+ <link rel="shortcut icon" href="/files/favicon_white.ico" media="(prefers-color-scheme: dark)">
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+ <link rel="shortcut icon" href="/files/favicon.ico" media="(prefers-color-scheme: light)">
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+
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+ <link rel="stylesheet" href="/manual/resources/lesson.css">
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+ <link rel="stylesheet" href="/manual/resources/lang.css">
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+ <!-- Import maps polyfill -->
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+ <!-- Remove this when import maps will be widely supported -->
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+ <script async src="https://unpkg.com/[email protected]/dist/es-module-shims.js"></script>
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+
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+ <script type="importmap">
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{
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"imports": {
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"three": "../../build/three.module.js"
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}
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}
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</script>
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- <link rel="stylesheet" href="/manual/zh/lang.css">
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- </head>
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- <body>
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- <div class="container">
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- <div class="lesson-title">
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- <h1>Indexed Textures for Picking and Color</h1>
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- </div>
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- <div class="lesson">
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- <div class="lesson-main">
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- <p>抱歉，还没有中文翻译哦。 <a href="https://github.com/mrdoob/three.js">欢迎加入翻译</a>! 😄</p>
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-<p><a href="/manual/en/indexed-textures.html">英文原文链接</a>.</p>
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+ <link rel="stylesheet" href="/manual/zh/lang.css">
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+</head>
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+
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+<body>
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+ <div class="container">
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+ <div class="lesson-title">
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+ <h1>使用纹理索引来拾取和着色</h1>
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+ </div>
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+ <div class="lesson">
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+ <div class="lesson-main">
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+ <p>这篇文章是 <a href="align-html-elements-to-3d.html">对齐HTML元素到3D对象</a> 的延续。
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+ 如果你还没有读过上篇文章，你应该先从那里开始，然后再回来继续阅读。</p>
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+ <p>有时候使用Three.js需要提出一些创造性的解决思路。我不确定这是一个很好的解决方案，但我想我会分享它，你可以看看是否可以为你的需求提供了一些解决思路或方案。</p>
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+ <p>在 <a href="align-html-elements-to-3d.html">上一篇文章中</a>，我们在3D地球周围显示了国家名称，那么我们如何做到，让用户选中一个国家并高亮他的选择？</p>
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+ <p>第一个想法是为每个国家生成几何图形，我们可以 <a href="picking.html">使用射线拾取</a> ，就像之前介绍的那样。
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+ 我们将为每个国家构建3D几何对象。如果用户点击代表那个国家的网格对象，我们就会知道对应的国家被点击了。</p>
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+ <p>所以，为了验证这个解决方案，我尝试生成所有国家的3D网格对象，使用了<a href="align-html-elements-to-3d.html">在上一篇文章中</a>和我生成轮廓一样的数据。
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+ 结果生成了15.5m的二进制GLTF(.glb)文件，让用户下载15.5m的数据对于我来说实在太多了。
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+ </p>
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+ <p>有很多方法可以压缩数据。第一种可能是应用一些算法来降低轮廓的分辨率，但是我没有花时间来研究它。可能出现美国边界变大而加拿大边界变小的情况。</p>
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+ <p>另一种解决方案是仅使用数据压缩，比如gzip将其降至11m，这减少了30%，但是还不够。</p>
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+ <p>我们可以将所有数据存储为16位而不是32位浮点值。或者我们也可以使用像<a href="https://google.github.io/draco/">draco 压缩</a>
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+ 这种东西也许就够了。不过我没有去试，我推荐你去试下回来告诉我是怎么回事，因为我很想知道😅</p>
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+ <p>就我而言，我考虑使用 <a href="picking.html">GPU拾取方案</a>，
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+ 这在上一篇 <a href="picking.html">关于拾取的文章</a> 的最后有提到。这种方案中，我们使用一种独特的颜色代表不同网格对象的ID，然后我们绘制了所有网格，看看哪个颜色被点击了。</p>
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+ <p>基于这种灵感，我们可以预先生成一张国家的地图，每个国家的颜色是它在国家数组中的索引号。我们可以使用类似GPU拾取技术，我们使用索引纹理绘制一个离屏全局画布，查看颜色会告诉我们用户点击了那个国家ID。</p>
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+ <p>因此，我 <a href="https://github.com/mrdoob/three.js/blob/master/manual/resources/tools/geo-picking/">写了一些代码</a>
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+ 生成这样的一个纹理，在这里： </p>
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+ <div class="threejs_center"><img src="../examples/resources/data/world/country-index-texture.png"
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+ style="width: 700px;"></div>
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+
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+ <p>注意：生成这份纹理的数据来源于 <a href="http://thematicmapping.org/downloads/world_borders.php">这个网站</a>
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+ ，使用的协议是 <a href="http://creativecommons.org/licenses/by-sa/3.0/">CC-BY-SA</a>。</p>
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+ <p>它只有217k，比国家网格对象的15m要好得多，事实上我们可以使用更低的分辨率，但现在217k似乎已经足够了。</p>
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+ <p>所以让我们试着用它来选择国家。</p>
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+ <p>从 <a href="picking.html">GPU拾取案例中</a> 获取代码，我们需要一个场景来做拾取。</p>
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+ <pre class="prettyprint showlinemods notranslate lang-js" translate="no">const pickingScene = new THREE.Scene();
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+pickingScene.background = new THREE.Color(0);
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+</pre>
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+ <p>我们需要将带有索引纹理的地球添加到拾取场景中。</p>
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+ <pre class="prettyprint showlinemods notranslate lang-js" translate="no">{
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+ const loader = new THREE.TextureLoader();
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+ const geometry = new THREE.SphereGeometry(1, 64, 32);
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+
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++ const indexTexture = loader.load('resources/data/world/country-index-texture.png', render);
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++ indexTexture.minFilter = THREE.NearestFilter;
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++ indexTexture.magFilter = THREE.NearestFilter;
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++
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++ const pickingMaterial = new THREE.MeshBasicMaterial({map: indexTexture});
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++ pickingScene.add(new THREE.Mesh(geometry, pickingMaterial));
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+
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+ const texture = loader.load('resources/data/world/country-outlines-4k.png', render);
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+ const material = new THREE.MeshBasicMaterial({map: texture});
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+ scene.add(new THREE.Mesh(geometry, material));
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+}
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+</pre>
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+ <p>然后我们把 <code class="notranslate" translate="no">GPUPickingHelper</code>这个类拷贝下，在使用前我们需要做一些小改动</p>
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+ <pre class="prettyprint showlinemods notranslate lang-js" translate="no">class GPUPickHelper {
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+ constructor() {
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+ // 创造一个 1x1 的渲染对象
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+ this.pickingTexture = new THREE.WebGLRenderTarget(1, 1);
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+ this.pixelBuffer = new Uint8Array(4);
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+- this.pickedObject = null;
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+- this.pickedObjectSavedColor = 0;
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+ }
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+ pick(cssPosition, scene, camera) {
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+ const {pickingTexture, pixelBuffer} = this;
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+
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+ // 将视图偏移设置为仅表示鼠标下单个元素
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+ const pixelRatio = renderer.getPixelRatio();
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+ camera.setViewOffset(
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+ renderer.getContext().drawingBufferWidth, // full width
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+ renderer.getContext().drawingBufferHeight, // full top
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+ cssPosition.x * pixelRatio | 0, // rect x
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+ cssPosition.y * pixelRatio | 0, // rect y
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+ 1, // rect width
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+ 1, // rect height
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+ );
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+ // 渲染场景
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+ renderer.setRenderTarget(pickingTexture);
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+ renderer.render(scene, camera);
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+ renderer.setRenderTarget(null);
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+ // 清除视图偏移，使渲染恢复正常
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+ camera.clearViewOffset();
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+ // 读取像素
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+ renderer.readRenderTargetPixels(
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+ pickingTexture,
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+ 0, // x
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+ 0, // y
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+ 1, // width
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+ 1, // height
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+ pixelBuffer);
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+
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++ const id =
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++ (pixelBuffer[0] << 16) |
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++ (pixelBuffer[1] << 8) |
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++ (pixelBuffer[2] << 0);
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++
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++ return id;
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+- const id =
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+- (pixelBuffer[0] << 16) |
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+- (pixelBuffer[1] << 8) |
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+- (pixelBuffer[2] );
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+- const intersectedObject = idToObject[id];
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+- if (intersectedObject) {
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+- // 获取第一个对象，它是离我们最近的
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+- this.pickedObject = intersectedObject;
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+- // 保存它的颜色
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+- this.pickedObjectSavedColor = this.pickedObject.material.emissive.getHex();
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+- // 将其自发光颜色设置为闪烁的红色/黄色
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+- this.pickedObject.material.emissive.setHex((time * 8) % 2 > 1 ? 0xFFFF00 : 0xFF0000);
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+- }
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+ }
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+}
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+</pre>
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+ <p>现在我们可以用它来选择国家了。</p>
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+ <pre class="prettyprint showlinemods notranslate lang-js" translate="no">const pickHelper = new GPUPickHelper();
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+
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+function getCanvasRelativePosition(event) {
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+ const rect = canvas.getBoundingClientRect();
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+ return {
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+ x: (event.clientX - rect.left) * canvas.width / rect.width,
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+ y: (event.clientY - rect.top ) * canvas.height / rect.height,
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+ };
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+}
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+
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+function pickCountry(event) {
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+ // 如果我们还没有加载好数据，退出
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+ if (!countryInfos) {
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+ return;
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+ }
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+
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+ const position = getCanvasRelativePosition(event);
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+ const id = pickHelper.pick(position, pickingScene, camera);
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+ if (id > 0) {
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+ // 我们点击了一个国家，修改它的selected属性
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+ const countryInfo = countryInfos[id - 1];
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+ const selected = !countryInfo.selected;
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+ // 如果我们选中这个国家，并且没有按住控制键，取消所有选中的国家
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+ if (selected && !event.shiftKey && !event.ctrlKey && !event.metaKey) {
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+ unselectAllCountries();
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+ }
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+ numCountriesSelected += selected ? 1 : -1;
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+ countryInfo.selected = selected;
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+ } else if (numCountriesSelected) {
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+ // 海洋或者天空被选中了
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+ unselectAllCountries();
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+ }
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+ requestRenderIfNotRequested();
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+}
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+
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+function unselectAllCountries() {
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+ numCountriesSelected = 0;
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+ countryInfos.forEach((countryInfo) => {
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+ countryInfo.selected = false;
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+ });
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+}
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+
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+canvas.addEventListener('pointerup', pickCountry);
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+</pre>
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+ <p>上面的代码，设置/重置了国家数组元素的 <code class="notranslate" translate="no">selected</code> 属性。如果 <code class="notranslate"
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+ translate="no">shift</code> 或 <code class="notranslate" translate="no">ctrl</code> 或 <code
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+ class="notranslate" translate="no">cmd</code>
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+ 被按下了，你就可以选择多个国家。</p>
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+ <p>剩下的就是显示选择的国家，现在让我们更新标签</p>
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+ <pre class="prettyprint showlinemods notranslate lang-js" translate="no">function updateLabels() {
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+ // 如果我们还没有加载好数据，退出
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+ if (!countryInfos) {
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+ return;
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+ }
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+
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+ const large = settings.minArea * settings.minArea;
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+ // 获取表示相机正对方向的矩阵
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+ normalMatrix.getNormalMatrix(camera.matrixWorldInverse);
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+ // 获取相机位置
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+ camera.getWorldPosition(cameraPosition);
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+ for (const countryInfo of countryInfos) {
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+- const {position, elem, area} = countryInfo;
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+- // 足够大了？
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+- if (area < large) {
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++ const {position, elem, area, selected} = countryInfo;
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++ const largeEnough = area >= large;
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++ const show = selected || (numCountriesSelected === 0 && largeEnough);
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++ if (!show) {
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+ elem.style.display = 'none';
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+ continue;
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+ }
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+
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+ ...
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+</pre>
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+ <p>通过上面的代码，我们就有能力拾取对应的国家了。</p>
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+ <p></p>
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+ <div translate="no" class="threejs_example_container notranslate">
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+ <div><iframe class="threejs_example notranslate" translate="no" style=" "
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+ src="/manual/examples/resources/editor.html?url=/manual/examples/indexed-textures-picking.html"></iframe>
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+ </div>
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+ <a class="threejs_center" href="/manual/examples/indexed-textures-picking.html" target="_blank">点击在新窗口打开</a>
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+ </div>
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+
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+ <p></p>
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+ <p>代码仍然会根据地区显示对应的国家。不过如果你点击一个，只会显示对应的标签。</p>
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+ <p>所以这似乎是选择国家的有效解决方案，但是如何突出显示选定的国家？</p>
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+ <p>我们可以从 <em>调色板图形算法</em> 中获取灵感。</p>
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+ <p><a href="https://en.wikipedia.org/wiki/Palette_%28computing%29">调色板算法</a>
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+ 或者 <a href="https://en.wikipedia.org/wiki/Indexed_color">索引颜色</a>
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+ 是被旧的系统，比如Atari 800、Amiga、NES、Super Nintendolder及IBM
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+ PCs所使用的。并非以RGBA的形式给每个颜色存储8位、每个像素至少32字节的位图，他们存储位图是8位或者更少。每个像素都是一个调色板的索引值，
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+ 所以举例一个像素值为3，表示“显示3号颜色值”，而定义3号颜色值的地方就叫“调色板”。</p>
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+ <p>在JavaScript中就像这样：</p>
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+ <pre class="prettyprint showlinemods notranslate lang-js" translate="no">const face7x7PixelImageData = [
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+ 0, 1, 1, 1, 1, 1, 0,
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+ 1, 0, 0, 0, 0, 0, 1,
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+ 1, 0, 2, 0, 2, 0, 1,
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+ 1, 0, 0, 0, 0, 0, 1,
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+ 1, 0, 3, 3, 3, 0, 1,
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+ 1, 0, 0, 0, 0, 0, 1,
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+ 0, 1, 1, 1, 1, 1, 1,
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+];
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+
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+const palette = [
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+ [255, 255, 255], // 白
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+ [ 0, 0, 0], // 黑
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+ [ 0, 255, 255], // 青
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+ [255, 0, 0], // 红
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+];
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+</pre>
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+ <p>图像数据中每个像素都是调色板的索引，如果你分析上面调色板的数据你会得到这个图像：</p>
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+ <div class="threejs_center"><img src="../resources/images/7x7-indexed-face.png"></div>
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+
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+ <p>
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+ 在我们的例子中，上面已经有一个用不同id代表不同国家的纹理了，所以我们可以通过调色板使用相同的纹理赋予每个国家各自的颜色。通过更改调色板颜色我们可以为单独的国家着色。比如通过设置整个调色板纹理为黑色，给某个国家使用不同的颜色，就可以凸显那个国家了。
|
|
|
+ </p>
|
|
|
+ <p>要做调色板索引的话，需要一些自定义着色器代码，让我们修改Three.js中默认的着色器，这样我们也可以根据需要使用照明或其他特性。</p>
|
|
|
+ <p>就像我们在 <a href="optimize-lots-of-objects-animated.html">大量移动物体的优化</a> 这篇文章中提到的，通过
|
|
|
+ <code class="notranslate" translate="no">onBeforeCompile</code> 属性，我们可以通过向材质添加函数来修改默认的着色器。
|
|
|
+ </p>
|
|
|
+ <p>默认的片元着色器在编译之前看起来就像这样：</p>
|
|
|
+ <pre class="prettyprint showlinemods notranslate lang-glsl" translate="no">#include <common>
|
|
|
+#include <color_pars_fragment>
|
|
|
+#include <uv_pars_fragment>
|
|
|
+#include <uv2_pars_fragment>
|
|
|
+#include <map_pars_fragment>
|
|
|
+#include <alphamap_pars_fragment>
|
|
|
+#include <aomap_pars_fragment>
|
|
|
+#include <lightmap_pars_fragment>
|
|
|
+#include <envmap_pars_fragment>
|
|
|
+#include <fog_pars_fragment>
|
|
|
+#include <specularmap_pars_fragment>
|
|
|
+#include <logdepthbuf_pars_fragment>
|
|
|
+#include <clipping_planes_pars_fragment>
|
|
|
+void main() {
|
|
|
+ #include <clipping_planes_fragment>
|
|
|
+ vec4 diffuseColor = vec4( diffuse, opacity );
|
|
|
+ #include <logdepthbuf_fragment>
|
|
|
+ #include <map_fragment>
|
|
|
+ #include <color_fragment>
|
|
|
+ #include <alphamap_fragment>
|
|
|
+ #include <alphatest_fragment>
|
|
|
+ #include <specularmap_fragment>
|
|
|
+ ReflectedLight reflectedLight = ReflectedLight( vec3( 0.0 ), vec3( 0.0 ), vec3( 0.0 ), vec3( 0.0 ) );
|
|
|
+ #ifdef USE_LIGHTMAP
|
|
|
+ reflectedLight.indirectDiffuse += texture2D( lightMap, vUv2 ).xyz * lightMapIntensity;
|
|
|
+ #else
|
|
|
+ reflectedLight.indirectDiffuse += vec3( 1.0 );
|
|
|
+ #endif
|
|
|
+ #include <aomap_fragment>
|
|
|
+ reflectedLight.indirectDiffuse *= diffuseColor.rgb;
|
|
|
+ vec3 outgoingLight = reflectedLight.indirectDiffuse;
|
|
|
+ #include <envmap_fragment>
|
|
|
+ gl_FragColor = vec4( outgoingLight, diffuseColor.a );
|
|
|
+ #include <premultiplied_alpha_fragment>
|
|
|
+ #include <tonemapping_fragment>
|
|
|
+ #include <encodings_fragment>
|
|
|
+ #include <fog_fragment>
|
|
|
+}
|
|
|
+</pre>
|
|
|
+ <p><a href="https://github.com/mrdoob/three.js/tree/dev/src/renderers/shaders/ShaderChunk">查看所有的片段</a>
|
|
|
+ 我们发现THREE.js使用了一个名为 <code class="notranslate" translate="no">diffuseColor</code> 的变量去管理基本材质颜色。它在这里设置： <code
|
|
|
+ class="notranslate" translate="no"><color_fragment></code> <a
|
|
|
+ href="https://github.com/mrdoob/three.js/blob/dev/src/renderers/shaders/ShaderChunk/color_fragment.glsl.js">片段</a>
|
|
|
+ 所以我们应该能够在这部分之后进行修改。</p>
|
|
|
+ <p><code class="notranslate" translate="no">diffuseColor</code>
|
|
|
+ 在这个时刻应该已经是从我们轮廓纹理中获取的颜色了，所以我们应该可以从调色盘中获取颜色，然后把他们和最终颜色混合。</p>
|
|
|
+ <p>就像我们 <a href="optimize-lots-of-objects-animated.html">之前做的那样</a> ，
|
|
|
+ 在<a href="/docs/#api/en/materials/Material.onBeforeCompile"><code class="notranslate"
|
|
|
+ translate="no">Material.onBeforeCompile</code></a>我们使用一个用来搜索和替换着色器代码的数组。
|
|
|
+ </p>
|
|
|
+ <pre class="prettyprint showlinemods notranslate lang-js" translate="no">{
|
|
|
+ const loader = new THREE.TextureLoader();
|
|
|
+ const geometry = new THREE.SphereGeometry(1, 64, 32);
|
|
|
+
|
|
|
+ const indexTexture = loader.load('resources/data/world/country-index-texture.png', render);
|
|
|
+ indexTexture.minFilter = THREE.NearestFilter;
|
|
|
+ indexTexture.magFilter = THREE.NearestFilter;
|
|
|
+
|
|
|
+ const pickingMaterial = new THREE.MeshBasicMaterial({map: indexTexture});
|
|
|
+ pickingScene.add(new THREE.Mesh(geometry, pickingMaterial));
|
|
|
+
|
|
|
++ const fragmentShaderReplacements = [
|
|
|
++ {
|
|
|
++ from: '#include <common>',
|
|
|
++ to: `
|
|
|
++ #include <common>
|
|
|
++ uniform sampler2D indexTexture;
|
|
|
++ uniform sampler2D paletteTexture;
|
|
|
++ uniform float paletteTextureWidth;
|
|
|
++ `,
|
|
|
++ },
|
|
|
++ {
|
|
|
++ from: '#include <color_fragment>',
|
|
|
++ to: `
|
|
|
++ #include <color_fragment>
|
|
|
++ {
|
|
|
++ vec4 indexColor = texture2D(indexTexture, vUv);
|
|
|
++ float index = indexColor.r * 255.0 + indexColor.g * 255.0 * 256.0;
|
|
|
++ vec2 paletteUV = vec2((index + 0.5) / paletteTextureWidth, 0.5);
|
|
|
++ vec4 paletteColor = texture2D(paletteTexture, paletteUV);
|
|
|
++ // diffuseColor.rgb += paletteColor.rgb; // 白轮廓
|
|
|
++ diffuseColor.rgb = paletteColor.rgb - diffuseColor.rgb; // 黑轮廓
|
|
|
++ }
|
|
|
++ `,
|
|
|
++ },
|
|
|
++ ];
|
|
|
|
|
|
+ const texture = loader.load('resources/data/world/country-outlines-4k.png', render);
|
|
|
+ const material = new THREE.MeshBasicMaterial({map: texture});
|
|
|
++ material.onBeforeCompile = function(shader) {
|
|
|
++ fragmentShaderReplacements.forEach((rep) => {
|
|
|
++ shader.fragmentShader = shader.fragmentShader.replace(rep.from, rep.to);
|
|
|
++ });
|
|
|
++ };
|
|
|
+ scene.add(new THREE.Mesh(geometry, material));
|
|
|
+}
|
|
|
+</pre>
|
|
|
+ <p>在上面可以看到我们添加了3个uniforms变量，<code class="notranslate" translate="no">indexTexture</code>, <code
|
|
|
+ class="notranslate" translate="no">paletteTexture</code>,
|
|
|
+ and <code class="notranslate" translate="no">paletteTextureWidth</code>。我们从 <code class="notranslate"
|
|
|
+ translate="no">indexTexture</code>
|
|
|
+ 获取颜色，并且把它转化成索引下标。 <code class="notranslate" translate="no">vUv</code>
|
|
|
+ 是由Three.js提供的纹理坐标。然后我们使用索引下标从调色板中获取颜色。然后我们使用当前的 <code class="notranslate"
|
|
|
+ translate="no">diffuseColor</code>和最终的结果作混合。
|
|
|
+ <code class="notranslate"
|
|
|
+ translate="no">diffuseColor</code>在此时是我们黑色纹理，而调色盘是白色纹理。所以如果我们相加两个颜色，得出的是白色轮廓。如果我们二者相减，得出的是黑色轮廓。
|
|
|
+ </p>
|
|
|
+ <p>在我们渲染前，我们还需要设置调色板纹理，以及这3个uniforms变量。</p>
|
|
|
+ <p>对于调色板纹理，它只需要足够宽即可。每个国家保留一种颜色 + 一种海洋颜色。这里有240个国家或地区，我们可以等到国家列表加载完成后以获取确切的数字来查找。不过选择一些更大的数字没有危害，所以让我们选择512。</p>
|
|
|
+ <p>这里是创建调色板的代码</p>
|
|
|
+ <pre class="prettyprint showlinemods notranslate lang-js" translate="no">const maxNumCountries = 512;
|
|
|
+const paletteTextureWidth = maxNumCountries;
|
|
|
+const paletteTextureHeight = 1;
|
|
|
+const palette = new Uint8Array(paletteTextureWidth * 4);
|
|
|
+const paletteTexture = new THREE.DataTexture(
|
|
|
+ palette, paletteTextureWidth, paletteTextureHeight);
|
|
|
+paletteTexture.minFilter = THREE.NearestFilter;
|
|
|
+paletteTexture.magFilter = THREE.NearestFilter;
|
|
|
+</pre>
|
|
|
+ <p>一个<a href="/docs/#api/en/textures/DataTexture"><code class="notranslate"
|
|
|
+ translate="no">DataTexture</code></a> 提供原始的纹理数据。在这种情况下，我们给他512个RGBA颜色，每个颜色4字节，每个包含0-255的红、绿、蓝分量。</p>
|
|
|
+ <p>让我们用随机颜色填充它，只是为了看看它是否有效</p>
|
|
|
+ <pre class="prettyprint showlinemods notranslate lang-js" translate="no">for (let i = 1; i < palette.length; ++i) {
|
|
|
+ palette[i] = Math.random() * 256;
|
|
|
+}
|
|
|
+// 设置海洋颜色 (索引 #0)
|
|
|
+palette.set([100, 200, 255, 255], 0);
|
|
|
+paletteTexture.needsUpdate = true;
|
|
|
+</pre>
|
|
|
+ <p>任何时候我们想要Three.js通过 <code class="notranslate" translate="no">palette</code> 数组的内容来更新调色板上的纹理，我们需要去设置<code
|
|
|
+ class="notranslate" translate="no">paletteTexture.needsUpdate</code>
|
|
|
+ 为 <code class="notranslate" translate="no">true</code>。</p>
|
|
|
+ <p>然后我们还需要设置材质上的uniforms变量</p>
|
|
|
+ <pre class="prettyprint showlinemods notranslate lang-js" translate="no">const geometry = new THREE.SphereGeometry(1, 64, 32);
|
|
|
+const material = new THREE.MeshBasicMaterial({map: texture});
|
|
|
+material.onBeforeCompile = function(shader) {
|
|
|
+ fragmentShaderReplacements.forEach((rep) => {
|
|
|
+ shader.fragmentShader = shader.fragmentShader.replace(rep.from, rep.to);
|
|
|
+ });
|
|
|
++ shader.uniforms.paletteTexture = {value: paletteTexture};
|
|
|
++ shader.uniforms.indexTexture = {value: indexTexture};
|
|
|
++ shader.uniforms.paletteTextureWidth = {value: paletteTextureWidth};
|
|
|
+};
|
|
|
+scene.add(new THREE.Mesh(geometry, material));
|
|
|
+</pre>
|
|
|
+ <p>这样我们就得到了随机着色的国家</p>
|
|
|
+ <p></p>
|
|
|
+ <div translate="no" class="threejs_example_container notranslate">
|
|
|
+ <div><iframe class="threejs_example notranslate" translate="no" style=" "
|
|
|
+ src="/manual/examples/resources/editor.html?url=/manual/examples/indexed-textures-random-colors.html"></iframe>
|
|
|
+ </div>
|
|
|
+ <a class="threejs_center" href="/manual/examples/indexed-textures-random-colors.html" target="_blank">click
|
|
|
+ here to open in a separate window</a>
|
|
|
+ </div>
|
|
|
+
|
|
|
+ <p></p>
|
|
|
+ <p>现在我们可以看到索引和调色板纹理生效了，让我们控制调色板进行高亮显示</p>
|
|
|
+ <p>首先让我们创建一个函数，我们传入一个THREE.js颜色，并格式化为可以放入调色板纹理的值。</p>
|
|
|
+ <pre class="prettyprint showlinemods notranslate lang-js" translate="no">const tempColor = new THREE.Color();
|
|
|
+function get255BasedColor(color) {
|
|
|
+ tempColor.set(color);
|
|
|
+ const base = tempColor.toArray().map(v => v * 255);
|
|
|
+ base.push(255); // alpha
|
|
|
+ return base;
|
|
|
+}
|
|
|
+</pre>
|
|
|
+ <p>像这样来调用 <code class="notranslate" translate="no">color = get255BasedColor('red')</code> 会返回一个像 <code
|
|
|
+ class="notranslate" translate="no">[255, 0, 0, 255]</code>这样的数组。</p>
|
|
|
+ <p>接下来让我们用它来生成一些颜色并填充调色板。</p>
|
|
|
+ <pre class="prettyprint showlinemods notranslate lang-js" translate="no">const selectedColor = get255BasedColor('red');
|
|
|
+const unselectedColor = get255BasedColor('#444');
|
|
|
+const oceanColor = get255BasedColor('rgb(100,200,255)');
|
|
|
+resetPalette();
|
|
|
+
|
|
|
+function setPaletteColor(index, color) {
|
|
|
+ palette.set(color, index * 4);
|
|
|
+}
|
|
|
+
|
|
|
+function resetPalette() {
|
|
|
+ // 让所有的颜色都是未选择状态的颜色
|
|
|
+ for (let i = 1; i < maxNumCountries; ++i) {
|
|
|
+ setPaletteColor(i, unselectedColor);
|
|
|
+ }
|
|
|
+
|
|
|
+ // 设置海洋颜色 (索引 #0)
|
|
|
+ setPaletteColor(0, oceanColor);
|
|
|
+ paletteTexture.needsUpdate = true;
|
|
|
+}
|
|
|
+</pre>
|
|
|
+ <p>现在让我们使用这些函数来更新调色板，当一个国家被选中时：</p>
|
|
|
+ <pre class="prettyprint showlinemods notranslate lang-js" translate="no">function getCanvasRelativePosition(event) {
|
|
|
+ const rect = canvas.getBoundingClientRect();
|
|
|
+ return {
|
|
|
+ x: (event.clientX - rect.left) * canvas.width / rect.width,
|
|
|
+ y: (event.clientY - rect.top ) * canvas.height / rect.height,
|
|
|
+ };
|
|
|
+}
|
|
|
+
|
|
|
+function pickCountry(event) {
|
|
|
+ // 如果我们还没有加载好数据，退出
|
|
|
+ if (!countryInfos) {
|
|
|
+ return;
|
|
|
+ }
|
|
|
+
|
|
|
+ const position = getCanvasRelativePosition(event);
|
|
|
+ const id = pickHelper.pick(position, pickingScene, camera);
|
|
|
+ if (id > 0) {
|
|
|
+ const countryInfo = countryInfos[id - 1];
|
|
|
+ const selected = !countryInfo.selected;
|
|
|
+ if (selected && !event.shiftKey && !event.ctrlKey && !event.metaKey) {
|
|
|
+ unselectAllCountries();
|
|
|
+ }
|
|
|
+ numCountriesSelected += selected ? 1 : -1;
|
|
|
+ countryInfo.selected = selected;
|
|
|
++ setPaletteColor(id, selected ? selectedColor : unselectedColor);
|
|
|
++ paletteTexture.needsUpdate = true;
|
|
|
+ } else if (numCountriesSelected) {
|
|
|
+ unselectAllCountries();
|
|
|
+ }
|
|
|
+ requestRenderIfNotRequested();
|
|
|
+}
|
|
|
+
|
|
|
+function unselectAllCountries() {
|
|
|
+ numCountriesSelected = 0;
|
|
|
+ countryInfos.forEach((countryInfo) => {
|
|
|
+ countryInfo.selected = false;
|
|
|
+ });
|
|
|
++ resetPalette();
|
|
|
+}
|
|
|
+</pre>
|
|
|
+ <p>我们应该能够突出显示1个或多个国家。</p>
|
|
|
+ <p></p>
|
|
|
+ <div translate="no" class="threejs_example_container notranslate">
|
|
|
+ <div><iframe class="threejs_example notranslate" translate="no" style=" "
|
|
|
+ src="/manual/examples/resources/editor.html?url=/manual/examples/indexed-textures-picking-and-highlighting.html"></iframe>
|
|
|
+ </div>
|
|
|
+ <a class="threejs_center" href="/manual/examples/indexed-textures-picking-and-highlighting.html"
|
|
|
+ target="_blank">点击在新窗口打开</a>
|
|
|
+ </div>
|
|
|
+
|
|
|
+ <p></p>
|
|
|
+ <p>这看起来有效！</p>
|
|
|
+ <p>一件小事是我们不能不改变选中状态就渲染地球。如果我们选择一个国家然后想要旋转地球，选中状态将改变。</p>
|
|
|
+ <p>让我们尝试解决这个问题。我认为，我们可以检查两件事情。点击和松开经过了多少时间；用户是否移动了鼠标。如果时间很短，或者他们没有移动鼠标，那么这个行为可能是点击。否则他们可能正在尝试拖动地球。</p>
|
|
|
+ <pre class="prettyprint showlinemods notranslate lang-js" translate="no">+const maxClickTimeMs = 200;
|
|
|
++const maxMoveDeltaSq = 5 * 5;
|
|
|
++const startPosition = {};
|
|
|
++let startTimeMs;
|
|
|
++
|
|
|
++function recordStartTimeAndPosition(event) {
|
|
|
++ startTimeMs = performance.now();
|
|
|
++ const pos = getCanvasRelativePosition(event);
|
|
|
++ startPosition.x = pos.x;
|
|
|
++ startPosition.y = pos.y;
|
|
|
++}
|
|
|
+
|
|
|
+function getCanvasRelativePosition(event) {
|
|
|
+ const rect = canvas.getBoundingClientRect();
|
|
|
+ return {
|
|
|
+ x: (event.clientX - rect.left) * canvas.width / rect.width,
|
|
|
+ y: (event.clientY - rect.top ) * canvas.height / rect.height,
|
|
|
+ };
|
|
|
+}
|
|
|
+
|
|
|
+function pickCountry(event) {
|
|
|
+ // exit if we have not loaded the data yet
|
|
|
+ if (!countryInfos) {
|
|
|
+ return;
|
|
|
+ }
|
|
|
+
|
|
|
++ // 如果用户触发后已经过了一段时间了
|
|
|
++ // 就认为这是一个拖动行为
|
|
|
++ const clickTimeMs = performance.now() - startTimeMs;
|
|
|
++ if (clickTimeMs > maxClickTimeMs) {
|
|
|
++ return;
|
|
|
++ }
|
|
|
++
|
|
|
++ // 如果鼠标移动了，就认为这是一个拖动行为
|
|
|
++ const position = getCanvasRelativePosition(event);
|
|
|
++ const moveDeltaSq = (startPosition.x - position.x) ** 2 +
|
|
|
++ (startPosition.y - position.y) ** 2;
|
|
|
++ if (moveDeltaSq > maxMoveDeltaSq) {
|
|
|
++ return;
|
|
|
++ }
|
|
|
+
|
|
|
+- const position = {x: event.clientX, y: event.clientY};
|
|
|
+ const id = pickHelper.pick(position, pickingScene, camera);
|
|
|
+ if (id > 0) {
|
|
|
+ const countryInfo = countryInfos[id - 1];
|
|
|
+ const selected = !countryInfo.selected;
|
|
|
+ if (selected && !event.shiftKey && !event.ctrlKey && !event.metaKey) {
|
|
|
+ unselectAllCountries();
|
|
|
+ }
|
|
|
+ numCountriesSelected += selected ? 1 : -1;
|
|
|
+ countryInfo.selected = selected;
|
|
|
+ setPaletteColor(id, selected ? selectedColor : unselectedColor);
|
|
|
+ paletteTexture.needsUpdate = true;
|
|
|
+ } else if (numCountriesSelected) {
|
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+ unselectAllCountries();
|
|
|
+ }
|
|
|
+ requestRenderIfNotRequested();
|
|
|
+}
|
|
|
+
|
|
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+function unselectAllCountries() {
|
|
|
+ numCountriesSelected = 0;
|
|
|
+ countryInfos.forEach((countryInfo) => {
|
|
|
+ countryInfo.selected = false;
|
|
|
+ });
|
|
|
+ resetPalette();
|
|
|
+}
|
|
|
+
|
|
|
++canvas.addEventListener('pointerdown', recordStartTimeAndPosition);
|
|
|
+canvas.addEventListener('pointerup', pickCountry);
|
|
|
+</pre>
|
|
|
+ <p>添加了这些操作，这<em>看起来</em> 对我有效。</p>
|
|
|
+ <p></p>
|
|
|
+ <div translate="no" class="threejs_example_container notranslate">
|
|
|
+ <div><iframe class="threejs_example notranslate" translate="no" style=" "
|
|
|
+ src="/manual/examples/resources/editor.html?url=/manual/examples/indexed-textures-picking-debounced.html"></iframe>
|
|
|
+ </div>
|
|
|
+ <a class="threejs_center" href="/manual/examples/indexed-textures-picking-debounced.html"
|
|
|
+ target="_blank">点击在新窗口打开</a>
|
|
|
</div>
|
|
|
+
|
|
|
+ <p></p>
|
|
|
+ <p>我不是用户交互的专家，所以我很想知道是否有更好的解决方案。</p>
|
|
|
+ <p>我希望这能让你了解图形索引的用处，以及如何修改Three.js的着色器以添加简单的功能。对于如何使用GLSL，编写着色器语言对于本文来说太多了，这个链接有一些少量的信息，参考
|
|
|
+ <a href="post-processing.html">关于后处理的这篇文章</a>。
|
|
|
+ </p>
|
|
|
+
|
|
|
</div>
|
|
|
</div>
|
|
|
-
|
|
|
+ </div>
|
|
|
+
|
|
|
<script src="/manual/resources/prettify.js"></script>
|
|
|
<script src="/manual/resources/lesson.js"></script>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
-</body></html>
|
|
|
+</body>
|
|
|
+
|
|
|
+</html>
|
MongooseSong