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267 lines
14 KiB
267 lines
14 KiB
3 years ago
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<!DOCTYPE html><html lang="en"><head>
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<meta charset="utf-8">
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<title>Backgrounds and Skyboxes</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 – Backgrounds and Skyboxes">
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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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<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/es-module-shims@1.3.6/dist/es-module-shims.js"></script>
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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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</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>Backgrounds and Skyboxes</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>Most of the articles here use a solid color for a background.</p>
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<p>Adding as static background can be as simple as setting some CSS. Taking
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an example from <a href="responsive.html">the article on making THREE.js responsive</a>
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we only need to change 2 things.</p>
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<p>We need to add some CSS to our canvas to set its background to an image</p>
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<pre class="prettyprint showlinemods notranslate lang-html" translate="no"><style>
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body {
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margin: 0;
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}
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#c {
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width: 100%;
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height: 100%;
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display: block;
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+ background: url(resources/images/daikanyama.jpg) no-repeat center center;
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+ background-size: cover;
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}
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</style>
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</pre>
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<p>and we need to tell the <a href="/docs/#api/en/renderers/WebGLRenderer"><code class="notranslate" translate="no">WebGLRenderer</code></a> to use <code class="notranslate" translate="no">alpha</code> so places we are not
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drawing anything are transparent.</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">function main() {
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const canvas = document.querySelector('#c');
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- const renderer = new THREE.WebGLRenderer({canvas});
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+ const renderer = new THREE.WebGLRenderer({
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+ canvas,
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+ alpha: true,
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+ });
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</pre>
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<p>And we get a background.</p>
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<p></p><div translate="no" class="threejs_example_container notranslate">
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<div><iframe class="threejs_example notranslate" translate="no" style=" " src="/manual/examples/resources/editor.html?url=/manual/examples/background-css.html"></iframe></div>
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<a class="threejs_center" href="/manual/examples/background-css.html" target="_blank">click here to open in a separate window</a>
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</div>
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<p></p>
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<p>If we want the background to be able to be affected by <a href="post-processing.html">post processing
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effects</a> then we need to draw the background using
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THREE.js.</p>
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<p>THREE.js makes this some what simple. We can just set the background of the scene to
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a texture.</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const loader = new THREE.TextureLoader();
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const bgTexture = loader.load('resources/images/daikanyama.jpg');
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scene.background = bgTexture;
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</pre>
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<p>which gives us</p>
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<p></p><div translate="no" class="threejs_example_container notranslate">
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<div><iframe class="threejs_example notranslate" translate="no" style=" " src="/manual/examples/resources/editor.html?url=/manual/examples/background-scene-background.html"></iframe></div>
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<a class="threejs_center" href="/manual/examples/background-scene-background.html" target="_blank">click here to open in a separate window</a>
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</div>
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<p></p>
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<p>This gets us a background image but its stretched to fit the screen.</p>
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<p>We can solve this issue by setting the <code class="notranslate" translate="no">repeat</code> and <code class="notranslate" translate="no">offset</code> properties of
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the texture to show only a portion of image.</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">function render(time) {
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...
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+ // Set the repeat and offset properties of the background texture
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+ // to keep the image's aspect correct.
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+ // Note the image may not have loaded yet.
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+ const canvasAspect = canvas.clientWidth / canvas.clientHeight;
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+ const imageAspect = bgTexture.image ? bgTexture.image.width / bgTexture.image.height : 1;
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+ const aspect = imageAspect / canvasAspect;
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+
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+ bgTexture.offset.x = aspect > 1 ? (1 - 1 / aspect) / 2 : 0;
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+ bgTexture.repeat.x = aspect > 1 ? 1 / aspect : 1;
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+
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+ bgTexture.offset.y = aspect > 1 ? 0 : (1 - aspect) / 2;
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+ bgTexture.repeat.y = aspect > 1 ? 1 : aspect;
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...
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renderer.render(scene, camera);
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requestAnimationFrame(render);
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}
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</pre>
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<p>and now THREE.js drawing the background. There is no visible difference from
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the CSS version at the top but now if we used a <a href="post-processing.html">post processing
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effect</a> the background would be affected too.</p>
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<p></p><div translate="no" class="threejs_example_container notranslate">
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<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>
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<a class="threejs_center" href="/manual/examples/background-scene-background-fixed-aspect.html" target="_blank">click here to open in a separate window</a>
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</div>
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<p></p>
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<p>Of course a static background is not usually what we want in a 3D scene. Instead
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we usually want some kind of <em>skybox</em>. A skybox is just that, box with the sky
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draw on it. We put the camera inside the box and it looks like there is a sky in
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the background.</p>
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<p>The most common way to implement a skybox is to make a cube, apply a texture to
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it, draw it from the inside. On each side of the cube put a texture (using
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texture coordinates) that looks like some image of the horizon. It's also often
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common to use a sky sphere or a sky dome with a texture drawn on it. You can
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probably figure that one out on your own. Just make a cube or sphere,
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<a href="textures.html">apply a texture</a>, mark it as <code class="notranslate" translate="no">THREE.BackSide</code> so we
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render the inside instead of the outside, and either put it in your scene directly
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or like above, or, make 2 scenes, a special one to draw the skybox/sphere/dome and the
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normal one to draw everything else. You'd use your normal <a href="/docs/#api/en/cameras/PerspectiveCamera"><code class="notranslate" translate="no">PerspectiveCamera</code></a> to
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draw. No need for the <a href="/docs/#api/en/cameras/OrthographicCamera"><code class="notranslate" translate="no">OrthographicCamera</code></a>.</p>
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<p>Another solution is to use a <em>Cubemap</em>. A Cubemap is a special kind of texture
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that has 6 sides, the sides of a cube. Instead of using standard texture
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coordinates it uses a direction from the center pointing outward to decide where
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to get a color.</p>
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<p>Here are the 6 images of a cubemap from the computer history museum in Mountain
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View, California.</p>
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<div class="threejs_center">
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<img src="../examples/resources/images/cubemaps/computer-history-museum/pos-x.jpg" style="width: 200px" class="border">
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<img src="../examples/resources/images/cubemaps/computer-history-museum/neg-x.jpg" style="width: 200px" class="border">
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<img src="../examples/resources/images/cubemaps/computer-history-museum/pos-y.jpg" style="width: 200px" class="border">
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</div>
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<div class="threejs_center">
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<img src="../examples/resources/images/cubemaps/computer-history-museum/neg-y.jpg" style="width: 200px" class="border">
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<img src="../examples/resources/images/cubemaps/computer-history-museum/pos-z.jpg" style="width: 200px" class="border">
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<img src="../examples/resources/images/cubemaps/computer-history-museum/neg-z.jpg" style="width: 200px" class="border">
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</div>
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<p>To use them we use <a href="/docs/#api/en/loaders/CubeTextureLoader"><code class="notranslate" translate="no">CubeTextureLoader</code></a> to load them and then use that as a the
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scene's background.</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">{
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const loader = new THREE.CubeTextureLoader();
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const texture = loader.load([
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'resources/images/cubemaps/computer-history-museum/pos-x.jpg',
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'resources/images/cubemaps/computer-history-museum/neg-x.jpg',
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'resources/images/cubemaps/computer-history-museum/pos-y.jpg',
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'resources/images/cubemaps/computer-history-museum/neg-y.jpg',
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'resources/images/cubemaps/computer-history-museum/pos-z.jpg',
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'resources/images/cubemaps/computer-history-museum/neg-z.jpg',
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]);
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scene.background = texture;
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}
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</pre>
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<p>At render time we don't need to adjust the texture like we did above</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">function render(time) {
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...
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- // Set the repeat and offset properties of the background texture
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- // to keep the image's aspect correct.
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- // Note the image may not have loaded yet.
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- const canvasAspect = canvas.clientWidth / canvas.clientHeight;
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- const imageAspect = bgTexture.image ? bgTexture.image.width / bgTexture.image.height : 1;
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- const aspect = imageAspect / canvasAspect;
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-
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- bgTexture.offset.x = aspect > 1 ? (1 - 1 / aspect) / 2 : 0;
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- bgTexture.repeat.x = aspect > 1 ? 1 / aspect : 1;
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-
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- bgTexture.offset.y = aspect > 1 ? 0 : (1 - aspect) / 2;
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- bgTexture.repeat.y = aspect > 1 ? 1 : aspect;
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...
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renderer.render(scene, camera);
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requestAnimationFrame(render);
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}
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</pre>
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<p>Let's add some controls in so we can rotate the camera.</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">import {OrbitControls} from 'three/addons/controls/OrbitControls.js';
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</pre>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const fov = 75;
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const aspect = 2; // the canvas default
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const near = 0.1;
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-const far = 5;
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+const far = 100;
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const camera = new THREE.PerspectiveCamera(fov, aspect, near, far);
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-camera.position.z = 2;
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+camera.position.z = 3;
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+const controls = new OrbitControls(camera, canvas);
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+controls.target.set(0, 0, 0);
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+controls.update();
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</pre>
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<p>and try it out. Drag on the example to rotate the camera and see the cubemap
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surrounds us.</p>
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<p></p><div translate="no" class="threejs_example_container notranslate">
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<div><iframe class="threejs_example notranslate" translate="no" style=" " src="/manual/examples/resources/editor.html?url=/manual/examples/background-cubemap.html"></iframe></div>
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<a class="threejs_center" href="/manual/examples/background-cubemap.html" target="_blank">click here to open in a separate window</a>
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</div>
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<p></p>
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<p>Another option is to use an Equirectangular map. This is the kind of picture a
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<a href="https://google.com/search?q=360+camera">360 camera</a> takes.</p>
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<p><a href="https://hdrihaven.com/hdri/?h=tears_of_steel_bridge">Here's one</a> I found from
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<a href="https://hdrihaven.com">this site</a>.</p>
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<div class="threejs_center"><img src="../examples/resources/images/equirectangularmaps/tears_of_steel_bridge_2k.jpg" style="width: 600px"></div>
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<p>It's not much different. First we load the equirectangular image as a texture
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and then, in the callback after it has loaded, we can call <a href="/docs/#api/en/renderers/WebGLCubeRenderTarget.fromEquirectangularTexture"><code class="notranslate" translate="no">WebGLCubeRenderTarget.fromEquirectangularTexture</code></a>
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which will generate a cubemap from the equirectangular texture for us.
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We pass in the size we want the cubemap to be to <a href="/docs/#api/en/renderers/WebGLCubeRenderTarget"><code class="notranslate" translate="no">WebGLCubeRenderTarget</code></a>.
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Passing in the height of the equirectangular image seems like a good bet.</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">{
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- const loader = new THREE.CubeTextureLoader();
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- const texture = loader.load([
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- 'resources/images/cubemaps/computer-history-museum/pos-x.jpg',
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- 'resources/images/cubemaps/computer-history-museum/neg-x.jpg',
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- 'resources/images/cubemaps/computer-history-museum/pos-y.jpg',
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- 'resources/images/cubemaps/computer-history-museum/neg-y.jpg',
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- 'resources/images/cubemaps/computer-history-museum/pos-z.jpg',
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- 'resources/images/cubemaps/computer-history-museum/neg-z.jpg',
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- ]);
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- scene.background = texture;
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+ const loader = new THREE.TextureLoader();
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+ const texture = loader.load(
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+ 'resources/images/equirectangularmaps/tears_of_steel_bridge_2k.jpg',
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+ () => {
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+ const rt = new THREE.WebGLCubeRenderTarget(texture.image.height);
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+ rt.fromEquirectangularTexture(renderer, texture);
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+ scene.background = rt.texture;
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+ });
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}
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</pre>
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<p>And that's all there is to it.</p>
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<p></p><div translate="no" class="threejs_example_container notranslate">
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<div><iframe class="threejs_example notranslate" translate="no" style=" " src="/manual/examples/resources/editor.html?url=/manual/examples/background-equirectangularmap.html"></iframe></div>
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<a class="threejs_center" href="/manual/examples/background-equirectangularmap.html" target="_blank">click here to open in a separate window</a>
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</div>
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<p></p>
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<p>Rather than do it at load time you can also convert an equirectangular image
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to a cubemap beforehand. <a href="https://matheowis.github.io/HDRI-to-CubeMap/">Here's a site that will do it for you</a>.</p>
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</div>
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</div>
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</div>
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<script src="/manual/resources/prettify.js"></script>
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<script src="/manual/resources/lesson.js"></script>
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</body></html>
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