y the distance, the lower the detail on the mesh. * * @param {Object3D} object - The 3D object to display at this level. * @param {number} [distance=0] - The distance at which to display this level of detail. * @param {number} [hysteresis=0] - Threshold used to avoid flickering at LOD boundaries, as a fraction of distance. * @return {LOD} A reference to this instance. */ addLevel( object, distance = 0, hysteresis = 0 ) { distance = Math.abs( distance ); const levels = this.levels; let l; for ( l = 0; l < levels.length; l ++ ) { if ( distance < levels[ l ].distance ) { break; } } levels.splice( l, 0, { distance: distance, hysteresis: hysteresis, object: object } ); this.add( object ); return this; } /** * Removes an existing level, based on the distance from the camera. * Returns `true` when the level has been removed. Otherwise `false`. * * @param {number} distance - Distance of the level to remove. * @return {boolean} Whether the level has been removed or not. */ removeLevel( distance ) { const levels = this.levels; for ( let i = 0; i < levels.length; i ++ ) { if ( levels[ i ].distance === distance ) { const removedElements = levels.splice( i, 1 ); this.remove( removedElements[ 0 ].object ); return true; } } return false; } /** * Returns the currently active LOD level index. * * @return {number} The current active LOD level index. */ getCurrentLevel() { return this._currentLevel; } /** * Returns a reference to the first 3D object that is greater than * the given distance. * * @param {number} distance - The LOD distance. * @return {?Object3D} The found 3D object. `null` if no 3D object has been found. */ getObjectForDistance( distance ) { const levels = this.levels; if ( levels.length > 0 ) { let i, l; for ( i = 1, l = levels.length; i < l; i ++ ) { let levelDistance = levels[ i ].distance; if ( levels[ i ].object.visible ) { levelDistance -= levelDistance * levels[ i ].hysteresis; } if ( distance < levelDistance ) { break; } } return levels[ i - 1 ].object; } return null; } /** * Computes intersection points between a casted ray and this LOD. * * @param {Raycaster} raycaster - The raycaster. * @param {Array