computeFrenetFrames( segments, closed = false ) {

		// see http://www.cs.indiana.edu/pub/techreports/TR425.pdf

		const normal = new Vector3();

		const tangents = [];
		const normals = [];
		const binormals = [];

		const vec = new Vector3();
		const mat = new Matrix4();

		// compute the tangent vectors for each segment on the curve

		for ( let i = 0; i <= segments; i ++ ) {

			const u = i / segments;

			tangents[ i ] = this.getTangentAt( u, new Vector3() );

		}

		// select an initial normal vector perpendicular to the first tangent vector,
		// and in the direction of the minimum tangent xyz component

		normals[ 0 ] = new Vector3();
		binormals[ 0 ] = new Vector3();
		let min = Number.MAX_VALUE;
		const tx = Math.abs( tangents[ 0 ].x );
		const ty = Math.abs( tangents[ 0 ].y );
		const tz = Math.abs( tangents[ 0 ].z );

		if ( tx <= min ) {

			min = tx;
			normal.set( 1, 0, 0 );

		}

		if ( ty <= min ) {

			min = ty;
			normal.set( 0, 1, 0 );

		}

		if ( tz <= min ) {

			normal.set( 0, 0, 1 );

		}

		vec.crossVectors( tangents[ 0 ], normal ).normalize();

		normals[ 0 ].crossVectors( tangents[ 0 ], vec );
		binormals[ 0 ].crossVectors( tangents[ 0 ], normals[ 0 ] );


		// compute the slowly-varying normal and binormal vectors for each segment on the curve

		for ( let i = 1; i <= segments; i ++ ) {

			normals[ i ] = normals[ i - 1 ].clone();

			binormals[ i ] = binormals[ i - 1 ].clone();

			vec.crossVectors( tangents[ i - 1 ], tangents[ i ] );

			if ( vec.length() > Number.EPSILON ) {

				vec.normalize();

				const theta = Math.acos( clamp( tangents[ i - 1 ].dot( tangents[ i ] ), -1, 1 ) ); // clamp for floating pt errors

				normals[ i ].applyMatrix4( mat.makeRotationAxis( vec, theta ) );

			}

			binormals[ i ].crossVectors( tangents[ i ], normals[ i ] );

		}

		// if the curve is closed, postprocess the vectors so the first and last normal vectors are the same

		if ( closed === true ) {

			let theta = Math.acos( clamp( normals[ 0 ].dot( normals[ segments ] ), -1, 1 ) );
			theta /= segments;

			if ( tangents[ 0 ].dot( vec.crossVectors( normals[ 0 ], normals[ segments ] ) ) > 0 ) {

				theta = - theta;

			}

			for ( let i = 1; i <= segments; i ++ ) {

				// twist a little...
				normals[ i ].applyMatrix4( mat.makeRotationAxis( tangents[ i ], theta * i ) );
				binormals[ i ].crossVectors( tangents[ i ], normals[ i ] );

			}

		}

		return {
			tangents: tangents,
			normals: normals,
			binormals: binormals
		};

	}
Generates the Frenet Frames. Requires a curve definition in 3D space. Used
in geometries like {@link TubeGeometry} or {@link ExtrudeGeometry}.

@param {number} segments - The number of segments.
@param {boolean} [closed=false] - Whether the curve is closed or not.
@return {{tangents: Array<Vector3>, normals: Array<Vector3>, binormals: Array<Vector3>}} The Frenet Frames.