function WireframeGeometry( geometry ) {

		BufferGeometry.call( this );

		this.type = 'WireframeGeometry';

		// buffer

		var vertices = [];

		// helper variables

		var i, j, l, o, ol;
		var edge = [ 0, 0 ], edges = {}, e;
		var key, keys = [ 'a', 'b', 'c' ];
		var vertex;

		// different logic for Geometry and BufferGeometry

		if ( geometry && geometry.isGeometry ) {

			// create a data structure that contains all edges without duplicates

			var faces = geometry.faces;

			for ( i = 0, l = faces.length; i < l; i ++ ) {

				var face = faces[ i ];

				for ( j = 0; j < 3; j ++ ) {

					edge[ 0 ] = face[ keys[ j ] ];
					edge[ 1 ] = face[ keys[ ( j + 1 ) % 3 ] ];
					edge.sort( sortFunction ); // sorting prevents duplicates

					key = edge.toString();

					if ( edges[ key ] === undefined ) {

						edges[ key ] = { index1: edge[ 0 ], index2: edge[ 1 ] };

					}

				}

			}

			// generate vertices

			for ( key in edges ) {

				e = edges[ key ];

				vertex = geometry.vertices[ e.index1 ];
				vertices.push( vertex.x, vertex.y, vertex.z );

				vertex = geometry.vertices[ e.index2 ];
				vertices.push( vertex.x, vertex.y, vertex.z );

			}

		} else if ( geometry && geometry.isBufferGeometry ) {

			var position, indices, groups;
			var group, start, count;
			var index1, index2;

			vertex = new Vector3();

			if ( geometry.index !== null ) {

				// indexed BufferGeometry

				position = geometry.attributes.position;
				indices = geometry.index;
				groups = geometry.groups;

				if ( groups.length === 0 ) {

					geometry.addGroup( 0, indices.count );

				}

				// create a data structure that contains all eges without duplicates

				for ( o = 0, ol = groups.length; o < ol; ++ o ) {

					group = groups[ o ];

					start = group.start;
					count = group.count;

					for ( i = start, l = ( start + count ); i < l; i += 3 ) {

						for ( j = 0; j < 3; j ++ ) {

							edge[ 0 ] = indices.getX( i + j );
							edge[ 1 ] = indices.getX( i + ( j + 1 ) % 3 );
							edge.sort( sortFunction ); // sorting prevents duplicates

							key = edge.toString();

							if ( edges[ key ] === undefined ) {

								edges[ key ] = { index1: edge[ 0 ], index2: edge[ 1 ] };

							}

						}

					}

				}

				// generate vertices

				for ( key in edges ) {

					e = edges[ key ];

					vertex.fromBufferAttribute( position, e.index1 );
					vertices.push( vertex.x, vertex.y, vertex.z );

					vertex.fromBufferAttribute( position, e.index2 );
					vertices.push( vertex.x, vertex.y, vertex.z );

				}

			} else {

				// non-indexed BufferGeometry

				position = geometry.attributes.position;

				for ( i = 0, l = ( position.count / 3 ); i < l; i ++ ) {

					for ( j = 0; j < 3; j ++ ) {

						// three edges per triangle, an edge is represented as (index1, index2)
						// e.g. the first triangle has the following edges: (0,1),(1,2),(2,0)

						index1 = 3 * i + j;
						vertex.fromBufferAttribute( position, index1 );
						vertices.push( vertex.x, vertex.y, vertex.z );

						index2 = 3 * i + ( ( j + 1 ) % 3 );
						vertex.fromBufferAttribute( position, index2 );
						vertices.push( vertex.x, vertex.y, vertex.z );

					}

				}

			}

		}

		// build geometry

		this.addAttribute( 'position', new Float32BufferAttribute( vertices, 3 ) );

		// custom array sort function

		function sortFunction( a, b ) {

			return a - b;

		}

	}
@author mrdoob / http://mrdoob.com/
@author Mugen87 / https://github.com/Mugen87