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

/**
 * @author zz85 / http://www.lab4games.net/zz85/blog
 *
 **/

/**************************************************************
 *  Curved Path - a curve path is simply a array of connected
 *  curves, but retains the api of a curve
 **************************************************************/

THREE.CurvePath = function () {

    this.curves = [];
    this.bends = [];
    
    this.autoClose = false; // Automatically closes the path
};

THREE.CurvePath.prototype = Object.create( THREE.Curve.prototype );

THREE.CurvePath.prototype.add = function ( curve ) {

    this.curves.push( curve );

};

THREE.CurvePath.prototype.checkConnection = function() {
    // TODO
    // If the ending of curve is not connected to the starting
    // or the next curve, then, this is not a real path
};

THREE.CurvePath.prototype.closePath = function() {
    // TODO Test
    // and verify for vector3 (needs to implement equals)
    // Add a line curve if start and end of lines are not connected
    var startPoint = this.curves[0].getPoint(0);
    var endPoint = this.curves[this.curves.length-1].getPoint(1);
    
    if (!startPoint.equals(endPoint)) {
        this.curves.push( new THREE.LineCurve(endPoint, startPoint) );
    }
    
};

// To get accurate point with reference to
// entire path distance at time t,
// following has to be done:

// 1. Length of each sub path have to be known
// 2. Locate and identify type of curve
// 3. Get t for the curve
// 4. Return curve.getPointAt(t')

THREE.CurvePath.prototype.getPoint = function( t ) {

    var d = t * this.getLength();
    var curveLengths = this.getCurveLengths();
    var i = 0, diff, curve;

    // To think about boundaries points.

    while ( i < curveLengths.length ) {

        if ( curveLengths[ i ] >= d ) {

            diff = curveLengths[ i ] - d;
            curve = this.curves[ i ];

            var u = 1 - diff / curve.getLength();

            return curve.getPointAt( u );

            break;
        }

        i ++;

    }

    return null;

    // loop where sum != 0, sum > d , sum+1 <d

};

/*
THREE.CurvePath.prototype.getTangent = function( t ) {
};*/


// We cannot use the default THREE.Curve getPoint() with getLength() because in
// THREE.Curve, getLength() depends on getPoint() but in THREE.CurvePath
// getPoint() depends on getLength

THREE.CurvePath.prototype.getLength = function() {

    var lens = this.getCurveLengths();
    return lens[ lens.length - 1 ];

};

// Compute lengths and cache them
// We cannot overwrite getLengths() because UtoT mapping uses it.

THREE.CurvePath.prototype.getCurveLengths = function() {

    // We use cache values if curves and cache array are same length

    if ( this.cacheLengths && this.cacheLengths.length == this.curves.length ) {

        return this.cacheLengths;

    };

    // Get length of subsurve
    // Push sums into cached array

    var lengths = [], sums = 0;
    var i, il = this.curves.length;

    for ( i = 0; i < il; i ++ ) {

        sums += this.curves[ i ].getLength();
        lengths.push( sums );

    }

    this.cacheLengths = lengths;

    return lengths;

};



// Returns min and max coordinates, as well as centroid

THREE.CurvePath.prototype.getBoundingBox = function () {

    var points = this.getPoints();

    var maxX, maxY, maxZ;
    var minX, minY, minZ;

    maxX = maxY = Number.NEGATIVE_INFINITY;
    minX = minY = Number.POSITIVE_INFINITY;

    var p, i, il, sum;

    var v3 = points[0] instanceof THREE.Vector3;

    sum = v3 ? new THREE.Vector3() : new THREE.Vector2();

    for ( i = 0, il = points.length; i < il; i ++ ) {

        p = points[ i ];

        if ( p.x > maxX ) maxX = p.x;
        else if ( p.x < minX ) minX = p.x;

        if ( p.y > maxY ) maxY = p.y;
        else if ( p.y < minY ) minY = p.y;

        if ( v3 ) {

            if ( p.z > maxZ ) maxZ = p.z;
            else if ( p.z < minZ ) minZ = p.z;

        }

        sum.add( p );

    }

    var ret = {

        minX: minX,
        minY: minY,
        maxX: maxX,
        maxY: maxY,
        centroid: sum.divideScalar( il )

    };

    if ( v3 ) {

        ret.maxZ = maxZ;
        ret.minZ = minZ;

    }

    return ret;

};

/**************************************************************
 *  Create Geometries Helpers
 **************************************************************/

/// Generate geometry from path points (for Line or ParticleSystem objects)

THREE.CurvePath.prototype.createPointsGeometry = function( divisions ) {

    var pts = this.getPoints( divisions, true );
    return this.createGeometry( pts );

};

// Generate geometry from equidistance sampling along the path

THREE.CurvePath.prototype.createSpacedPointsGeometry = function( divisions ) {

    var pts = this.getSpacedPoints( divisions, true );
    return this.createGeometry( pts );

};

THREE.CurvePath.prototype.createGeometry = function( points ) {

    var geometry = new THREE.Geometry();

    for ( var i = 0; i < points.length; i ++ ) {

        geometry.vertices.push( new THREE.Vector3( points[ i ].x, points[ i ].y, points[ i ].z || 0) );

    }

    return geometry;

};


/**************************************************************
 *  Bend / Wrap Helper Methods
 **************************************************************/

// Wrap path / Bend modifiers?

THREE.CurvePath.prototype.addWrapPath = function ( bendpath ) {

    this.bends.push( bendpath );

};

THREE.CurvePath.prototype.getTransformedPoints = function( segments, bends ) {

    var oldPts = this.getPoints( segments ); // getPoints getSpacedPoints
    var i, il;

    if ( !bends ) {

        bends = this.bends;

    }

    for ( i = 0, il = bends.length; i < il; i ++ ) {

        oldPts = this.getWrapPoints( oldPts, bends[ i ] );

    }

    return oldPts;

};

THREE.CurvePath.prototype.getTransformedSpacedPoints = function( segments, bends ) {

    var oldPts = this.getSpacedPoints( segments );

    var i, il;

    if ( !bends ) {

        bends = this.bends;

    }

    for ( i = 0, il = bends.length; i < il; i ++ ) {

        oldPts = this.getWrapPoints( oldPts, bends[ i ] );

    }

    return oldPts;

};

// This returns getPoints() bend/wrapped around the contour of a path.
// Read http://www.planetclegg.com/projects/WarpingTextToSplines.html

THREE.CurvePath.prototype.getWrapPoints = function ( oldPts, path ) {

    var bounds = this.getBoundingBox();

    var i, il, p, oldX, oldY, xNorm;

    for ( i = 0, il = oldPts.length; i < il; i ++ ) {

        p = oldPts[ i ];

        oldX = p.x;
        oldY = p.y;

        xNorm = oldX / bounds.maxX;

        // If using actual distance, for length > path, requires line extrusions
        //xNorm = path.getUtoTmapping(xNorm, oldX); // 3 styles. 1) wrap stretched. 2) wrap stretch by arc length 3) warp by actual distance

        xNorm = path.getUtoTmapping( xNorm, oldX );

        // check for out of bounds?

        var pathPt = path.getPoint( xNorm );
        var normal = path.getTangent( xNorm );
        normal.set( -normal.y, normal.x ).multiplyScalar( oldY );

        p.x = pathPt.x + normal.x;
        p.y = pathPt.y + normal.y;

    }

    return oldPts;

};