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213 lines
7.9 KiB
213 lines
7.9 KiB
2 years ago
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<!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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<h1>光线投射[name]</h1>
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<p class="desc">
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这个类用于进行[link:https://en.wikipedia.org/wiki/Ray_casting raycasting]（光线投射）。
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光线投射用于进行鼠标拾取（在三维空间中计算出鼠标移过了什么物体）。
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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 raycaster = new THREE.Raycaster();
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const pointer = new THREE.Vector2();
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function onPointerMove( event ) {
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// 将鼠标位置归一化为设备坐标。x 和 y 方向的取值范围是 (-1 to +1)
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pointer.x = ( event.clientX / window.innerWidth ) * 2 - 1;
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pointer.y = - ( event.clientY / window.innerHeight ) * 2 + 1;
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}
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function render() {
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// 通过摄像机和鼠标位置更新射线
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raycaster.setFromCamera( pointer, camera );
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// 计算物体和射线的焦点
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const intersects = raycaster.intersectObjects( scene.children );
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for ( let i = 0; i < intersects.length; i ++ ) {
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intersects[ i ].object.material.color.set( 0xff0000 );
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}
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renderer.render( scene, camera );
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}
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window.addEventListener( 'pointermove', onPointerMove );
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window.requestAnimationFrame(render);
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</code>
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<h2>例子</h2>
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<p>
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[example:webgl_interactive_cubes Raycasting to a Mesh]<br />
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[example:webgl_interactive_cubes_ortho Raycasting to a Mesh in using an OrthographicCamera]<br />
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[example:webgl_interactive_buffergeometry Raycasting to a Mesh with BufferGeometry]<br />
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[example:webgl_instancing_raycast Raycasting to a InstancedMesh]<br />
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[example:webgl_interactive_lines Raycasting to a Line]<br />
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[example:webgl_interactive_raycasting_points Raycasting to Points]<br />
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[example:webgl_geometry_terrain_raycast Terrain raycasting]<br />
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[example:webgl_interactive_voxelpainter Raycasting to paint voxels]<br />
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[example:webgl_raycaster_texture Raycast to a Texture]
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</p>
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<p>
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</p>
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<h2>构造器</h2>
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<h3>[name]( [param:Vector3 origin], [param:Vector3 direction], [param:Float near], [param:Float far] )</h3>
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<p>
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[page:Vector3 origin] —— 光线投射的原点向量。<br />
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[page:Vector3 direction] —— 向射线提供方向的方向向量，应当被标准化。<br />
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[page:Float near] —— 返回的所有结果比near远。near不能为负值，其默认值为0。<br />
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[page:Float far] —— 返回的所有结果都比far近。far不能小于near，其默认值为Infinity（正无穷。）</p>
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<p>
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这将创建一个新的raycaster对象。<br />
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</p>
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<h2>属性</h2>
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<h3>[property:Float far]</h3>
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<p>
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raycaster的远距离因数（投射远点）。这个值表明哪些对象可以基于该距离而被raycaster所丢弃。
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这个值不应当为负，并且应当比near属性大。
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</p>
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<h3>[property:Float near]</h3>
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<p>
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raycaster的近距离因数（投射近点）。这个值表明哪些对象可以基于该距离而被raycaster所丢弃。
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这个值不应当为负，并且应当比far属性小。
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</p>
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<h3>[property:Camera camera]</h3>
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<p>
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The camera to use when raycasting against view-dependent objects such as billboarded objects like [page:Sprites]. This field
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can be set manually or is set when calling "setFromCamera".
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Defaults to null.
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</p>
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<h3>[property:Layers layers]</h3>
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<p>
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Used by [name] to selectively ignore 3D objects when performing intersection tests. The following code example ensures that
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only 3D objects on layer *1* will be honored by the instance of [name].
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<code>
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raycaster.layers.set( 1 );
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object.layers.enable( 1 );
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</code>
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</p>
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<h3>[property:Object params]</h3>
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<p>
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具有以下属性的对象：
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<code>
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{
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Mesh: {},
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Line: { threshold: 1 },
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LOD: {},
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Points: { threshold: 1 },
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Sprite: {}
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}
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</code>
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Where threshold is the precision of the raycaster when intersecting objects, in world units.
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</p>
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<h3>[property:Ray ray]</h3>
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<p>用于进行光线投射的[Page:Ray]（射线）。</p>
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<h2>方法</h2>
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<h3>[method:undefined set]( [param:Vector3 origin], [param:Vector3 direction] )</h3>
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<p>
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[page:Vector3 origin] —— 光线投射的原点向量。<br />
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[page:Vector3 direction] —— 为光线提供方向的标准化方向向量。
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</p>
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<p>
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使用一个新的原点和方向来更新射线。
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</p>
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<h3>[method:undefined setFromCamera]( [param:Vector2 coords], [param:Camera camera] )</h3>
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<p>
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[page:Vector2 coords] —— 在标准化设备坐标中鼠标的二维坐标 —— X分量与Y分量应当在-1到1之间。<br />
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[page:Camera camera] —— 射线所来源的摄像机。
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</p>
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<p>
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使用一个新的原点和方向来更新射线。
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</p>
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<h3>[method:Array intersectObject]( [param:Object3D object], [param:Boolean recursive], [param:Array optionalTarget] )</h3>
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<p>
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[page:Object3D object] —— 检查与射线相交的物体。<br />
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[page:Boolean recursive] —— 若为true，则同时也会检查所有的后代。否则将只会检查对象本身。默认值为true。<br />
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[page:Array optionalTarget] — （可选）设置结果的目标数组。如果不设置这个值，则一个新的[page:Array]会被实例化；如果设置了这个值，则在每次调用之前必须清空这个数组（例如：array.length = 0;）。
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</p>
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<p>
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检测所有在射线与物体之间，包括或不包括后代的相交部分。返回结果时，相交部分将按距离进行排序，最近的位于第一个。<br>
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该方法返回一个包含有交叉部分的数组:
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</p>
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<code>
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[ { distance, point, face, faceIndex, object }, ... ]
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</code>
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<p>
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[page:Float distance] —— 射线投射原点和相交部分之间的距离。<br />
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[page:Vector3 point] —— 相交部分的点（世界坐标）<br />
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[page:Object face] —— 相交的面<br />
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[page:Integer faceIndex] —— 相交的面的索引<br />
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[page:Object3D object] —— 相交的物体<br />
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[page:Vector2 uv] —— 相交部分的点的UV坐标。<br />
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[page:Vector2 uv2] —— Second set of U,V coordinates at point of intersection<br />
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[page:Integer instanceId] – The index number of the instance where the ray intersects the InstancedMesh
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</p>
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<p>
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当计算这条射线是否和物体相交的时候，*Raycaster*将传入的对象委托给[page:Object3D.raycast raycast]方法。
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这将可以让[page:Mesh mesh]对于光线投射的响应不同于[page:Line lines]和[page:Points pointclouds]。
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</p>
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<p>
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<strong>请注意</strong>：对于网格来说，面必须朝向射线的原点，以便其能够被检测到。
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用于交互的射线穿过面的背侧时，将不会被检测到。如果需要对物体中面的两侧进行光线投射，
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你需要将[page:Mesh.material material]中的[page:Material.side side]属性设置为*THREE.DoubleSide*。
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</p>
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<h3>[method:Array intersectObjects]( [param:Array objects], [param:Boolean recursive], [param:Array optionalTarget] )</h3>
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<p>
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[page:Array objects] —— 检测和射线相交的一组物体。<br />
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[page:Boolean recursive] —— 若为true，则同时也会检测所有物体的后代。否则将只会检测对象本身的相交部分。默认值为true。<br />
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[page:Array optionalTarget] —— （可选）设置结果的目标数组。如果不设置这个值，则一个新的[page:Array]会被实例化；如果设置了这个值，则在每次调用之前必须清空这个数组（例如：array.length = 0;）。
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</p>
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<p>
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检测所有在射线与这些物体之间，包括或不包括后代的相交部分。返回结果时，相交部分将按距离进行排序，最近的位于第一个），相交部分和[page:.intersectObject]所返回的格式是相同的。
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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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