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

/**
 * @author bhouston / http://exocortex.com
 * @author mrdoob / http://mrdoob.com/
 */

THREE.Triangle = function ( a, b, c ) {

    this.a = ( a !== undefined ) ? a : new THREE.Vector3();
    this.b = ( b !== undefined ) ? b : new THREE.Vector3();
    this.c = ( c !== undefined ) ? c : new THREE.Vector3();

};

THREE.Triangle.normal = function() {

    var v0 = new THREE.Vector3();

    return function ( a, b, c, optionalTarget ) {

        var result = optionalTarget || new THREE.Vector3();

        result.subVectors( c, b );
        v0.subVectors( a, b );
        result.cross( v0 );

        var resultLengthSq = result.lengthSq();
        if( resultLengthSq > 0 ) {

            return result.multiplyScalar( 1 / Math.sqrt( resultLengthSq ) );

        }

        return result.set( 0, 0, 0 );

    };

}();

// static/instance method to calculate barycoordinates
// based on: http://www.blackpawn.com/texts/pointinpoly/default.html
THREE.Triangle.barycoordFromPoint = function() {

    var v0 = new THREE.Vector3();
    var v1 = new THREE.Vector3();
    var v2 = new THREE.Vector3();

    return function ( point, a, b, c, optionalTarget ) {

        v0.subVectors( c, a );
        v1.subVectors( b, a );
        v2.subVectors( point, a );

        var dot00 = v0.dot( v0 );
        var dot01 = v0.dot( v1 );
        var dot02 = v0.dot( v2 );
        var dot11 = v1.dot( v1 );
        var dot12 = v1.dot( v2 );

        var denom = ( dot00 * dot11 - dot01 * dot01 );

        var result = optionalTarget || new THREE.Vector3();

        // colinear or singular triangle
        if( denom == 0 ) {
            // arbitrary location outside of triangle?
            // not sure if this is the best idea, maybe should be returning undefined
            return result.set( -2, -1, -1 );
        }

        var invDenom = 1 / denom;
        var u = ( dot11 * dot02 - dot01 * dot12 ) * invDenom;
        var v = ( dot00 * dot12 - dot01 * dot02 ) * invDenom;

        // barycoordinates must always sum to 1
        return result.set( 1 - u - v, v, u );

    };

}();

THREE.Triangle.containsPoint = function() {

    var v1 = new THREE.Vector3();

    return function ( point, a, b, c ) {

        var result = THREE.Triangle.barycoordFromPoint( point, a, b, c, v1 );

        return ( result.x >= 0 ) && ( result.y >= 0 ) && ( ( result.x + result.y ) <= 1 );

    };

}();

THREE.Triangle.prototype = {

    constructor: THREE.Triangle,

    set: function ( a, b, c ) {

        this.a.copy( a );
        this.b.copy( b );
        this.c.copy( c );

        return this;

    },

    setFromPointsAndIndices: function ( points, i0, i1, i2 ) {

        this.a.copy( points[i0] );
        this.b.copy( points[i1] );
        this.c.copy( points[i2] );

        return this;

    },

    copy: function ( triangle ) {

        this.a.copy( triangle.a );
        this.b.copy( triangle.b );
        this.c.copy( triangle.c );

        return this;

    },

    area: function() {

        var v0 = new THREE.Vector3();
        var v1 = new THREE.Vector3();

        return function () {

            v0.subVectors( this.c, this.b );
            v1.subVectors( this.a, this.b );

            return v0.cross( v1 ).length() * 0.5;

        };

    }(),

    midpoint: function ( optionalTarget ) {

        var result = optionalTarget || new THREE.Vector3();
        return result.addVectors( this.a, this.b ).add( this.c ).multiplyScalar( 1 / 3 );

    },

    normal: function ( optionalTarget ) {

        return THREE.Triangle.normal( this.a, this.b, this.c, optionalTarget );

    },

    plane: function ( optionalTarget ) {

        var result = optionalTarget || new THREE.Plane();

        return result.setFromCoplanarPoints( this.a, this.b, this.c );

    },

    barycoordFromPoint: function ( point, optionalTarget ) {

        return THREE.Triangle.barycoordFromPoint( point, this.a, this.b, this.c, optionalTarget );

    },

    containsPoint: function ( point ) {

        return THREE.Triangle.containsPoint( point, this.a, this.b, this.c );

    },

    equals: function ( triangle ) {

        return triangle.a.equals( this.a ) && triangle.b.equals( this.b ) && triangle.c.equals( this.c );

    },

    clone: function () {

        return new THREE.Triangle().copy( this );

    }

};