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127 lines
4.0 KiB
127 lines
4.0 KiB
<!DOCTYPE html>
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<html lang="zh">
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<head>
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<meta charset="utf-8" />
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<base href="../../../" />
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<script src="page.js"></script>
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<link type="text/css" rel="stylesheet" href="page.css" />
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</head>
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<body>
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[page:Object3D] →
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<h1>多细节层次（[name]，Levels of Detail）</h1>
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<p class="desc">
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多细节层次 —— 在显示网格时，根据摄像机距离物体的距离，来使用更多或者更少的几何体来对其进行显示。<br /><br />
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每一个级别都和一个几何体相关联，且在渲染时，可以根据给定的距离，来在这些级别对应的几何体之间进行切换。
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通常情况下，你会创建多个几何体，比如说三个，一个距离很远（低细节），一个距离适中（中等细节），还有一个距离非常近（高质量）。
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</p>
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<h2>代码示例</h2>
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<code>
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const lod = new THREE.LOD();
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//Create spheres with 3 levels of detail and create new LOD levels for them
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for( let i = 0; i < 3; i++ ) {
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const geometry = new THREE.IcosahedronGeometry( 10, 3 - i )
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const mesh = new THREE.Mesh( geometry, material );
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lod.addLevel( mesh, i * 75 );
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}
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scene.add( lod );
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</code>
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<h2>例子</h2>
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<p>
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[example:webgl_lod webgl / lod ]
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</p>
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<h2>Constructor</h2>
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<h3>[name]( )</h3>
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<p>
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创建一个新的 [name].
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</p>
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<h2>属性</h2>
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<p>共有属性请参见其基类[page:Object3D]。</p>
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<h3>[property:Boolean autoUpdate]</h3>
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<p>
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Whether the LOD object is updated automatically by the renderer per frame or not.
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If set to false, you have to call [page:LOD.update]() in the render loop by yourself.
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Default is true.
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</p>
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<h3>[property:Boolean isLOD]</h3>
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<p>
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Read-only flag to check if a given object is of type [name].
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</p>
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<h3>[property:Array levels]</h3>
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<p>
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一个包含有[page:Object level] objects（各层次物体）的数组。<br /><br />
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每一个层级都是一个对象，具有以下两个属性：
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[page:Object3D object] —— 在这个层次中将要显示的[page:Object3D]。<br />
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[page:Float distance] —— 将显示这一细节层次的距离。<br />
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[page:Float hysteresis] —— Threshold used to avoid flickering at LOD boundaries, as a fraction of distance.
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</p>
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<h2>方法</h2>
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<p>共有方法请参见其基类[page:Object3D]。</p>
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<h3>[method:this addLevel]( [param:Object3D object], [param:Float distance], [param:Float hysteresis] )</h3>
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<p>
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[page:Object3D object] —— 在这个层次中将要显示的[page:Object3D]。<br />
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[page:Float distance] —— 将显示这一细节层次的距离。<br />
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[page:Float hysteresis] —— Threshold used to avoid flickering at LOD boundaries, as a fraction of distance. Default 0.0.<br /><br />
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添加在一定距离和更大范围内显示的网格。通常来说，距离越远，网格中的细节就越少。
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</p>
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<h3>[method:LOD clone]()</h3>
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<p>
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返回一个LOD对象及其所关联的在特定距离中的物体。
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</p>
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<h3>[method:Integer getCurrentLevel]()</h3>
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<p>
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Get the currently active LOD level. As index of the levels array.
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</p>
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<h3>[method:Object3D getObjectForDistance]( [param:Float distance] )</h3>
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<p>
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获得第一个比[page:Float distance]大的[page:Object3D]（网格）的引用。
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</p>
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<h3>[method:undefined raycast]( [param:Raycaster raycaster], [param:Array intersects] )</h3>
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<p>
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在一条投射出去的[page:Ray]（射线）和这个LOD之间获得交互。
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[page:Raycaster.intersectObject]将会调用这个方法。
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</p>
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<h3>[method:Object toJSON]( meta )</h3>
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<p>
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使用这个方法，为LOD对象中的每个细节层次创建一个JSON结构。
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</p>
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<h3>[method:undefined update]( [param:Camera camera] )</h3>
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<p>
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基于每个[page:levels level]中的[page:Object3D object]和[page:Camera camera]（摄像机）之间的距离，来设置其可见性。
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</p>
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<h2>源代码</h2>
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<p>
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[link:https://github.com/mrdoob/three.js/blob/master/src/[path].js src/[path].js]
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</p>
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</body>
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</html>
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