source: other-projects/playing-in-the-street/summer-2013/trunk/Playing-in-the-Street-WPF/Content/Web/mrdoob-three.js-4862f5f/src/extras/helpers/EdgesHelper.js@ 28897

/**
 * @author WestLangley / http://github.com/WestLangley
 */

THREE.EdgesHelper = function ( object, hex ) {

    var color = ( hex !== undefined ) ? hex : 0xffffff;

    var edge = [ 0, 0 ], hash = {};
    var sortFunction = function ( a, b ) { return a - b };

    var keys = [ 'a', 'b', 'c' ];
    var geometry = new THREE.BufferGeometry();

    var geometry2 = object.geometry.clone();

    geometry2.mergeVertices();
    geometry2.computeFaceNormals();

    var vertices = geometry2.vertices;
    var faces = geometry2.faces;
    var numEdges = 0;

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

        var face = faces[ i ];

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

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

            var key = edge.toString();

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

                hash[ key ] = { vert1: edge[ 0 ], vert2: edge[ 1 ], face1: i, face2: undefined };
                numEdges ++;

            } else {

                hash[ key ].face2 = i;

            }

        }

    }

    geometry.addAttribute( 'position', Float32Array, 2 * numEdges, 3 );

    var coords = geometry.attributes.position.array;

    var index = 0;

    for ( var key in hash ) {

        var h = hash[ key ];

        if ( h.face2 === undefined || faces[ h.face1 ].normal.dot( faces[ h.face2 ].normal ) < 0.9999 ) { // hardwired const OK

            var vertex = vertices[ h.vert1 ];
            coords[ index ++ ] = vertex.x;
            coords[ index ++ ] = vertex.y;
            coords[ index ++ ] = vertex.z;

            vertex = vertices[ h.vert2 ];
            coords[ index ++ ] = vertex.x;
            coords[ index ++ ] = vertex.y;
            coords[ index ++ ] = vertex.z;

        }

    }

    THREE.Line.call( this, geometry, new THREE.LineBasicMaterial( { color: color } ), THREE.LinePieces );

    this.matrixAutoUpdate = false;
    this.matrixWorld = object.matrixWorld;

};

THREE.EdgesHelper.prototype = Object.create( THREE.Line.prototype );