( function () {

	class LineGeometry extends THREE.LineSegmentsGeometry {

		constructor() {

			super();
			this.isLineGeometry = true;
			this.type = 'LineGeometry';

		}

		setPositions( array ) {

			// converts [ x1, y1, z1,  x2, y2, z2, ... ] to pairs format
			const length = array.length - 3;
			const points = new Float32Array( 2 * length );

			for ( let i = 0; i < length; i += 3 ) {

				points[ 2 * i ] = array[ i ];
				points[ 2 * i + 1 ] = array[ i + 1 ];
				points[ 2 * i + 2 ] = array[ i + 2 ];
				points[ 2 * i + 3 ] = array[ i + 3 ];
				points[ 2 * i + 4 ] = array[ i + 4 ];
				points[ 2 * i + 5 ] = array[ i + 5 ];

			}

			super.setPositions( points );
			return this;

		}

		setColors( array ) {

			// converts [ r1, g1, b1,  r2, g2, b2, ... ] to pairs format
			const length = array.length - 3;
			const colors = new Float32Array( 2 * length );

			for ( let i = 0; i < length; i += 3 ) {

				colors[ 2 * i ] = array[ i ];
				colors[ 2 * i + 1 ] = array[ i + 1 ];
				colors[ 2 * i + 2 ] = array[ i + 2 ];
				colors[ 2 * i + 3 ] = array[ i + 3 ];
				colors[ 2 * i + 4 ] = array[ i + 4 ];
				colors[ 2 * i + 5 ] = array[ i + 5 ];

			}

			super.setColors( colors );
			return this;

		}

		fromLine( line ) {

			const geometry = line.geometry;
			this.setPositions( geometry.attributes.position.array ); // assumes non-indexed
			// set colors, maybe

			return this;

		}

	}

	THREE.LineGeometry = LineGeometry;

} )();