Sphere.js

/**
 * @author bhouston / http://clara.io
 * @author mrdoob / http://mrdoob.com/
 */

THREE.Sphere = function ( center, radius ) {

	this.center = ( center !== undefined ) ? center : new THREE.Vector3();
	this.radius = ( radius !== undefined ) ? radius : 0;

};

THREE.Sphere.prototype = {

	constructor: THREE.Sphere,

	set: function ( center, radius ) {

		this.center.copy( center );
		this.radius = radius;

		return this;

	},

	setFromPoints: function () {

		var box = new THREE.Box3();

		return function ( points, optionalCenter ) {

			var center = this.center;

			if ( optionalCenter !== undefined ) {

				center.copy( optionalCenter );

			} else {

				box.setFromPoints( points ).center( center );

			}

			var maxRadiusSq = 0;

			for ( var i = 0, il = points.length; i < il; i ++ ) {

				maxRadiusSq = Math.max( maxRadiusSq, center.distanceToSquared( points[ i ] ) );

			}

			this.radius = Math.sqrt( maxRadiusSq );

			return this;

		};

	}(),

	clone: function () {

		return new this.constructor().copy( this );

	},

	copy: function ( sphere ) {

		this.center.copy( sphere.center );
		this.radius = sphere.radius;

		return this;

	},

	empty: function () {

		return ( this.radius <= 0 );

	},

	containsPoint: function ( point ) {

		return ( point.distanceToSquared( this.center ) <= ( this.radius * this.radius ) );

	},

	distanceToPoint: function ( point ) {

		return ( point.distanceTo( this.center ) - this.radius );

	},

	intersectsSphere: function ( sphere ) {

		var radiusSum = this.radius + sphere.radius;

		return sphere.center.distanceToSquared( this.center ) <= ( radiusSum * radiusSum );

	},

	intersectsBox: function ( box ) {

		return box.intersectsSphere( this );

	},

	intersectsPlane: function ( plane ) {

		// We use the following equation to compute the signed distance from
		// the center of the sphere to the plane.
		//
		// distance = q * n - d
		//
		// If this distance is greater than the radius of the sphere,
		// then there is no intersection.

		return Math.abs( this.center.dot( plane.normal ) - plane.constant ) <= this.radius;

	},

	clampPoint: function ( point, optionalTarget ) {

		var deltaLengthSq = this.center.distanceToSquared( point );

		var result = optionalTarget || new THREE.Vector3();

		result.copy( point );

		if ( deltaLengthSq > ( this.radius * this.radius ) ) {

			result.sub( this.center ).normalize();
			result.multiplyScalar( this.radius ).add( this.center );

		}

		return result;

	},

	getBoundingBox: function ( optionalTarget ) {

		var box = optionalTarget || new THREE.Box3();

		box.set( this.center, this.center );
		box.expandByScalar( this.radius );

		return box;

	},

	applyMatrix4: function ( matrix ) {

		this.center.applyMatrix4( matrix );
		this.radius = this.radius * matrix.getMaxScaleOnAxis();

		return this;

	},

	translate: function ( offset ) {

		this.center.add( offset );

		return this;

	},

	equals: function ( sphere ) {

		return sphere.center.equals( this.center ) && ( sphere.radius === this.radius );

	}

};