_addNewFaces( eyeVertex, horizon ) {

		this.newFaces = [];

		let firstSideEdge = null;
		let previousSideEdge = null;

		for ( let i = 0; i < horizon.length; i ++ ) {

			const horizonEdge = horizon[ i ];

			// returns the right side edge

			const sideEdge = this._addAdjoiningFace( eyeVertex, horizonEdge );

			if ( firstSideEdge === null ) {

				firstSideEdge = sideEdge;

			} else {

				// joins face.getEdge( 1 ) with previousFace.getEdge( 0 )

				sideEdge.next.setTwin( previousSideEdge );

			}

			this.newFaces.push( sideEdge.face );
			previousSideEdge = sideEdge;

		}

		// perform final join of new faces

		firstSideEdge.next.setTwin( previousSideEdge );

		return this;

	}
Adds 'horizon.length' faces to the hull, each face will be linked with the horizon
opposite face and the face on the left/right.

@private
@param {VertexNode} eyeVertex - The vertex that is added to the hull.
@param {Array<HalfEdge>} horizon - The horizon.
@return {ConvexHull} A reference to this convex hull.