faceTriangulation.H

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/*---------------------------------------------------------------------------*\
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    \\  /    A nd           | Copyright (C) 1991-2010 OpenCFD Ltd.
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License
    This file is part of OpenFOAM.

    OpenFOAM is free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

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Class
    Foam::faceTriangulation

Description
    Triangulation of faces. Handles concave polygons as well
    (inefficiently)

    Works by trying to subdivide the face at the vertex with 'flattest'
    internal angle (i.e. closest to 180 deg).

    Based on routine 'Diagonal' in
    @verbatim
        "Efficient Triangulation of Simple Polygons"
        Godfried Toussaint, McGill University.
    @endverbatim

    After construction is the list of triangles the face is decomposed into.
    (Or empty list if no valid triangulation could be found).


SourceFiles
    faceTriangulation.C

\*---------------------------------------------------------------------------*/

#ifndef faceTriangulation_H
#define faceTriangulation_H

#include <OpenFOAM/triFaceList.H>
#include <OpenFOAM/pointField.H>

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

namespace Foam
{

// Forward declaration of classes

/*---------------------------------------------------------------------------*\
                           Class faceTriangulation Declaration
\*---------------------------------------------------------------------------*/

class faceTriangulation
:
    public triFaceList
{
    // Static Data

        //- Relative tolerance on edge.
        static const scalar edgeRelTol;


    // Static Member Functions

        //- Edge to the right of face vertex i
        static label right(const label size, label i);

        //- Edge to the left of face vertex i
        static label left(const label size, label i);

        //- Calculate normalized edge vectors
        static tmp<vectorField> calcEdges(const face&, const pointField&);

        //- Calculates half angle components of angle from e0 to e1
        //  in plane given by normal.
        static void calcHalfAngle
        (
            const vector& normal,
            const vector& e0,
            const vector& e1,
            scalar& cosHalfAngle,
            scalar& sinHalfAngle
        );

        //- Calculate intersection point between edge p1-p2 and ray (in 2D).
        // Return true and intersection point if intersection between p1 and p2.
        static pointHit rayEdgeIntersect
        (
            const vector& normal,
            const point& rayOrigin,
            const vector& rayDir,
            const point& p1,
            const point& p2,
            scalar& posOnEdge
        );

        // Return true if triangle given its three points
        // (anticlockwise ordered) contains point
        static bool triangleContainsPoint
        (
            const vector& n,
            const point& p0,
            const point& p1,
            const point& p2,
            const point& pt
        );

        //- Starting from startIndex find diagonal. Return in index1, index2.
        //  Index1 always startIndex except when convex polygon
        static void findDiagonal
        (
            const pointField& points,
            const face& f,
            const vectorField& edges,
            const vector& normal,
            const label startIndex,
            label& index1,
            label& index2
        );

        //- Find label of vertex to start splitting from. This will be the
        //  vertex with edge angle:
        //     1] flattest concave angle
        //     2] flattest convex angle if no concave angles.
        static label findStart
        (
            const face& f,
            const vectorField& edges,
            const vector& normal
        );


    // Private Member Functions

        //- Split face f into triangles. Handles all simple (convex & concave)
        //  polygons. Returns false if could not produce valid split.
        bool split
        (
            const bool fallBack,
            const pointField& points,
            const face& f,
            const vector& normal,
            label& triI
        );

public:

    // Constructors

        //- Construct null
        faceTriangulation();

        //- Construct from face and points. Decomposition based on average
        //  normal. After construction *this is size 0 or holds the triangles.
        //  If fallBack and triangulation fails does naive triangulation
        //  and never returns 0 size.
        faceTriangulation
        (
            const pointField& points,
            const face& f,
            const bool fallBack = false
        );

        //- Construct from face and points and user supplied (unit) normal.
        //  After construction *this is size 0 or holds the triangles.
        //  If fallBack and triangulation fails does naive triangulation
        //  and never returns 0 size.
        faceTriangulation
        (
            const pointField& points,
            const face& f,
            const vector& n,
            const bool fallBack = false
        );

        //- Construct from Istream
        faceTriangulation(Istream&);
};


// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

} // End namespace Foam

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

#endif

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