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- <title>背景与天空盒</title>
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- <h1>背景与天空盒</h1>
- </div>
- <div class="lesson">
- <div class="lesson-main">
- <p>这里大部分的文章都使用纯色作为背景。</p>
- <p>添加静态背景就像添加CSS一样简单,参考来自这篇<a href="responsive.html">THREE.js响应式编程</a>中的一个例子,我们只需要改变两个地方。
- </p>
- <p>我们需要在Canvas上添加一些CSS,以将其背景设置为图像。</p>
- <pre class="prettyprint showlinemods notranslate lang-html" translate="no"><style>
- body {
- margin: 0;
- }
- #c {
- width: 100%;
- height: 100%;
- display: block;
- + background: url(resources/images/daikanyama.jpg) no-repeat center center;
- + background-size: cover;
- }
- </style></pre>
- <p>然后我们需要告诉 <a href="/docs/#api/en/renderers/WebGLRenderer"><code class="notranslate"
- translate="no">WebGLRenderer</code></a> 去使用 <code class="notranslate"
- translate="no">alpha</code>,这样我们不绘制的地方都是透明的。
- </p>
- <pre class="prettyprint showlinemods notranslate lang-js" translate="no">function main() {
- const canvas = document.querySelector('#c');
- - const renderer = new THREE.WebGLRenderer({antialias: true, canvas});
- + const renderer = new THREE.WebGLRenderer({
- + antialias: true,
- + canvas,
- + alpha: true,
- + });</pre>
- <p>然后背景就有了。</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/background-css.html"></iframe></div>
- <a class="threejs_center" href="/manual/examples/background-css.html" target="_blank">点击在新窗口打开</a>
- </div>
- <p></p>
- <p>如果我们想让背景被 <a href="post-processing.html">后处理效果</a>影响,我们需要用THREE.js绘制背景。</p>
- <p>THREE.js 让这变得非常简单。我们可以将场景的背景设置为一种纹理。</p>
- <pre class="prettyprint showlinemods notranslate lang-js" translate="no">const loader = new THREE.TextureLoader();
- const bgTexture = loader.load('resources/images/daikanyama.jpg');
- bgTexture.colorSpace = THREE.SRGBColorSpace;
- scene.background = bgTexture;</pre>
- <p>效果如下</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/background-scene-background.html"></iframe>
- </div>
- <a class="threejs_center" href="/manual/examples/background-scene-background.html"
- target="_blank">点击在新窗口打开</a>
- </div>
- <p></p>
- <p>这产生了一个背景图,但它被拉伸以适应屏幕。</p>
- <p>我们可以解决这个问题,通过设置纹理属性 <code class="notranslate" translate="no">repeat</code> 和 <code class="notranslate"
- translate="no">offset</code> 来显示图像的一部分。</p>
- <pre class="prettyprint showlinemods notranslate lang-js" translate="no">function render(time) {
- ...
- + // 设置背景贴图的repeat和offset属性
- + // 来保证图片的比例是正确的
- + // 注意图片有可能还没加载完成
- + const canvasAspect = canvas.clientWidth / canvas.clientHeight;
- + const imageAspect = bgTexture.image ? bgTexture.image.width / bgTexture.image.height : 1;
- + const aspect = imageAspect / canvasAspect;
- +
- + bgTexture.offset.x = aspect > 1 ? (1 - 1 / aspect) / 2 : 0;
- + bgTexture.repeat.x = aspect > 1 ? 1 / aspect : 1;
- +
- + bgTexture.offset.y = aspect > 1 ? 0 : (1 - aspect) / 2;
- + bgTexture.repeat.y = aspect > 1 ? 1 : aspect;
- ...
- renderer.render(scene, camera);
- requestAnimationFrame(render);
- }</pre>
- <p>现在由 THREE.js 绘制背景。这个上面CSS的版本没有明显的区别,不过如果我们应用<a href="post-processing.html">后处理效果</a>,背景也会被影响。</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/background-scene-background-fixed-aspect.html"></iframe>
- </div>
- <a class="threejs_center" href="/manual/examples/background-scene-background-fixed-aspect.html"
- target="_blank">点击在新窗口打开</a>
- <p></p>
- <p>当然,静态背景通常不是我们在 3D 场景中想要的,相对的我们需要某种<em>天空盒</em>效果。就如字面意思,天空盒就是绘制了一片天空在盒子上。我们把相机放在盒子里,看起来里面有天空背景。</p>
- <p>
- 实现天空盒最常见的方法是制作一个立方体,应用纹理,绘制在它的内部。在立方体的每一面绘制一个纹理(使用纹理坐标),看起来像地平线的一些图像。通常使用带有纹理的天空球体或天空穹顶。你也许自己能想象得出来。只用一个立方体或球体,
- <a href="textures.html">应用纹理</a>, 标记它是 <code class="notranslate" translate="no">THREE.BackSide</code>
- ,这样我们渲染内部面而不是外部面,然后也把它直接放到场景里。或者使用两个场景,一个特殊的场景用于绘制天空盒/球体/圆顶,另一个画正常的一切。你可以用你正常的 <a
- href="/docs/#api/en/cameras/PerspectiveCamera"><code class="notranslate"
- translate="no">PerspectiveCamera</code></a> 去绘制,不需要<a
- href="/docs/#api/en/cameras/OrthographicCamera"><code class="notranslate"
- translate="no">OrthographicCamera</code></a>。
- </p>
- <p>另一个方法是使用<em>立方体贴图(Cubemap)</em>. 立方体贴图是一种特殊的纹理,它有6个立方体面,它不使用标准的纹理坐标,使用从中心指向外部的方向来决定绘制的颜色。</p>
- <p>这是来自加利福利亚,山景城的计算机历史博物馆的6张立方体图像。</p>
- <div class="threejs_center">
- <img src="../examples/resources/images/cubemaps/computer-history-museum/pos-x.jpg" style="width: 200px"
- class="border">
- <img src="../examples/resources/images/cubemaps/computer-history-museum/neg-x.jpg" style="width: 200px"
- class="border">
- <img src="../examples/resources/images/cubemaps/computer-history-museum/pos-y.jpg" style="width: 200px"
- class="border">
- </div>
- <div class="threejs_center">
- <img src="../examples/resources/images/cubemaps/computer-history-museum/neg-y.jpg" style="width: 200px"
- class="border">
- <img src="../examples/resources/images/cubemaps/computer-history-museum/pos-z.jpg" style="width: 200px"
- class="border">
- <img src="../examples/resources/images/cubemaps/computer-history-museum/neg-z.jpg" style="width: 200px"
- class="border">
- </div>
- <p>为了使用它们,我们使用<a href="/docs/#api/en/loaders/CubeTextureLoader"><code class="notranslate"
- translate="no">CubeTextureLoader</code></a> 加载它们,然后将其用作场景的背景。</p>
- <pre class="prettyprint showlinemods notranslate lang-js" translate="no">{
- const loader = new THREE.CubeTextureLoader();
- const texture = loader.load([
- 'resources/images/cubemaps/computer-history-museum/pos-x.jpg',
- 'resources/images/cubemaps/computer-history-museum/neg-x.jpg',
- 'resources/images/cubemaps/computer-history-museum/pos-y.jpg',
- 'resources/images/cubemaps/computer-history-museum/neg-y.jpg',
- 'resources/images/cubemaps/computer-history-museum/pos-z.jpg',
- 'resources/images/cubemaps/computer-history-museum/neg-z.jpg',
- ]);
- scene.background = texture;
- }</pre>
- <p>在渲染时,我们不需要像上面那样调整纹理:</p>
- <pre class="prettyprint showlinemods notranslate lang-js" translate="no">function render(time) {
- ...
- - // 设置背景贴图的repeat和offset属性
- - // 来保证图片的比例是正确的
- - // 注意图片有可能还没加载完成
- - const canvasAspect = canvas.clientWidth / canvas.clientHeight;
- - const imageAspect = bgTexture.image ? bgTexture.image.width / bgTexture.image.height : 1;
- - const aspect = imageAspect / canvasAspect;
- -
- - bgTexture.offset.x = aspect > 1 ? (1 - 1 / aspect) / 2 : 0;
- - bgTexture.repeat.x = aspect > 1 ? 1 / aspect : 1;
- -
- - bgTexture.offset.y = aspect > 1 ? 0 : (1 - aspect) / 2;
- - bgTexture.repeat.y = aspect > 1 ? 1 : aspect;
- ...
- renderer.render(scene, camera);
- requestAnimationFrame(render);
- }</pre>
- <p>让我们添加一些控件,以便我们可以旋转相机。</p>
- <pre class="prettyprint showlinemods notranslate lang-js"
- translate="no">import {OrbitControls} from 'three/addons/controls/OrbitControls.js';</pre>
- <pre class="prettyprint showlinemods notranslate lang-js" translate="no">const fov = 75;
- const aspect = 2; // Canvas默认值
- const near = 0.1;
- -const far = 5;
- +const far = 100;
- const camera = new THREE.PerspectiveCamera(fov, aspect, near, far);
- -camera.position.z = 2;
- +camera.position.z = 3;
- +const controls = new OrbitControls(camera, canvas);
- +controls.target.set(0, 0, 0);
- +controls.update();</pre>
- <p>来尝试下,拖动以旋转示例里的相机,观察围绕着我们的立方体贴图。</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/background-cubemap.html"></iframe>
- </div>
- <a class="threejs_center" href="/manual/examples/background-cubemap.html" target="_blank">点击在新窗口打开</a>
- </div>
- <p></p>
- <p>另一种选择是使用等距矩形贴图(Equirectangular map), 这是被
- <a href="https://google.com/search?q=360+camera">360 全景相机</a> 拍摄的一种特殊类型的图片。
- </p>
- <p><a href="https://hdrihaven.com/hdri/?h=tears_of_steel_bridge">这是一张图片</a>,我从
- <a href="https://hdrihaven.com">这个网站</a>找到的。
- </p>
- <div class="threejs_center"><img
- src="../examples/resources/images/equirectangularmaps/tears_of_steel_bridge_2k.jpg" style="width: 600px">
- </div>
- <p>这并不难,首先,我们将等距矩形图片加载为纹理, 我们可以调用 <a
- href="/docs/#api/en/renderers/WebGLCubeRenderTarget.fromEquirectangularTexture"><code class="notranslate"
- translate="no">WebGLCubeRenderTarget.fromEquirectangularTexture</code></a>
- 这将为我们从等距矩形纹理中生成一个立方体贴图,我们传入预期的立方体贴图的大小给 <a href="/docs/#api/en/renderers/WebGLCubeRenderTarget"><code
- class="notranslate" translate="no">WebGLCubeRenderTarget</code></a>,
- 使用等距矩形图片的高度似乎是一个不错的假设。</p>
- <pre class="prettyprint showlinemods notranslate lang-js" translate="no">{
- - const loader = new THREE.CubeTextureLoader();
- - const texture = loader.load([
- - 'resources/images/cubemaps/computer-history-museum/pos-x.jpg',
- - 'resources/images/cubemaps/computer-history-museum/neg-x.jpg',
- - 'resources/images/cubemaps/computer-history-museum/pos-y.jpg',
- - 'resources/images/cubemaps/computer-history-museum/neg-y.jpg',
- - 'resources/images/cubemaps/computer-history-museum/pos-z.jpg',
- - 'resources/images/cubemaps/computer-history-museum/neg-z.jpg',
- - ]);
- - scene.background = texture;
- + const loader = new THREE.TextureLoader();
- + const texture = loader.load(
- + 'resources/images/equirectangularmaps/tears_of_steel_bridge_2k.jpg',
- + () => {
- + texture.mapping = THREE.EquirectangularReflectionMapping;
- + texture.colorSpace = THREE.SRGBColorSpace;
- + scene.background = texture;
- + });
- }</pre>
- <p>这就是全部要做的事。</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/background-equirectangularmap.html"></iframe>
- </div>
- <a class="threejs_center" href="/manual/examples/background-equirectangularmap.html"
- target="_blank">点击在新窗口打开</a>
- </div>
- <p></p>
- <p>除了在加载时执行此操作,你还可以提前转换等距矩形到立方体贴图。<a href="https://matheowis.github.io/HDRI-to-CubeMap/">这是一个可以为你做这件事的网站</a>。
- </p>
- </div>
- </div>
- </div>
- </div>
- <script src="../resources/prettify.js"></script>
- <script src="../resources/lesson.js"></script>
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