Merge pull request #16214 from takahirox/ChainableAddLevel

Method chainable LOD.addLevel

docs/api/en/objects/LOD.html

@@ -72,7 +72,7 @@ scene.add( lod );
 		<h2>Methods</h2>
 		<p>See the base [page:Object3D] class for common methods.</p>
 
-		<h3>[method:null addLevel]( [param:Object3D object], [param:Float distance] )</h3>
+		<h3>[method:this addLevel]( [param:Object3D object], [param:Float distance] )</h3>
 		<p>
 		[page:Object3D object] - The [page:Object3D] to display at this level.<br />
 		[page:Float distance] - The distance at which to display this level of detail.<br /><br />

docs/api/zh/objects/LOD.html

@@ -69,7 +69,7 @@ scene.add( lod );
 		<h2>方法</h2>
 		<p>请参阅其基类[page:Object3D]来查看共有方法。</p>
 
-		<h3>[method:null addLevel]( [param:Object3D object], [param:Float distance] )</h3>
+		<h3>[method:this addLevel]( [param:Object3D object], [param:Float distance] )</h3>
 		<p>
 		[page:Object3D object] —— 在这个层次中将要显示的[page:Object3D]。<br />
 		[page:Float distance] —— 将显示这一细节层次的距离。<br /><br />

src/objects/LOD.d.ts

@@ -10,7 +10,7 @@ export class LOD extends Object3D {
 
   levels: { distance: number; object: Object3D }[];
 
-  addLevel(object: Object3D, distance?: number): void;
+  addLevel(object: Object3D, distance?: number): this;
   getObjectForDistance(distance: number): Object3D;
   raycast(raycaster: Raycaster, intersects: Intersection[]): void;
   update(camera: Camera): void;

src/objects/LOD.js

@@ -68,6 +68,8 @@ LOD.prototype = Object.assign( Object.create( Object3D.prototype ), {
 
 		this.add( object );
 
+		return this;
+
 	},
 
 	getObjectForDistance: function ( distance ) {