qwt_raster_data.cpp

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/* -*- mode: C++ ; c-file-style: "stroustrup" -*- *****************************
 * Qwt Widget Library
 * Copyright (C) 1997   Josef Wilgen
 * Copyright (C) 2002   Uwe Rathmann
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the Qwt License, Version 1.0
 *****************************************************************************/

#include "qwt_raster_data.h"
#include "qwt_point_3d.h"
#include <qnumeric.h>

class QwtRasterData::ContourPlane
{
public:
    explicit inline ContourPlane( double z ):
        d_z( z )
    {
    }

    inline bool intersect( const QwtPoint3D vertex[3],
        QPointF line[2], bool ignoreOnPlane ) const;

    inline double z() const { return d_z; }

private:
    inline int compare( double z ) const;
    inline QPointF intersection(
        const QwtPoint3D& p1, const QwtPoint3D &p2 ) const;

    double d_z;
};

inline bool QwtRasterData::ContourPlane::intersect(
    const QwtPoint3D vertex[3], QPointF line[2],
    bool ignoreOnPlane ) const
{
    bool found = true;

    // Are the vertices below (-1), on (0) or above (1) the plan ?
    const int eq1 = compare( vertex[0].z() );
    const int eq2 = compare( vertex[1].z() );
    const int eq3 = compare( vertex[2].z() );

    /*
        (a) All the vertices lie below the contour level.
        (b) Two vertices lie below and one on the contour level.
        (c) Two vertices lie below and one above the contour level.
        (d) One vertex lies below and two on the contour level.
        (e) One vertex lies below, one on and one above the contour level.
        (f) One vertex lies below and two above the contour level.
        (g) Three vertices lie on the contour level.
        (h) Two vertices lie on and one above the contour level.
        (i) One vertex lies on and two above the contour level.
        (j) All the vertices lie above the contour level.
     */

    static const int tab[3][3][3] =
    {
        // jump table to avoid nested case statements
        { { 0, 0, 8 }, { 0, 2, 5 }, { 7, 6, 9 } },
        { { 0, 3, 4 }, { 1, 10, 1 }, { 4, 3, 0 } },
        { { 9, 6, 7 }, { 5, 2, 0 }, { 8, 0, 0 } }
    };

    const int edgeType = tab[eq1+1][eq2+1][eq3+1];
    switch ( edgeType )
    {
        case 1:
            // d(0,0,-1), h(0,0,1)
            line[0] = vertex[0].toPoint();
            line[1] = vertex[1].toPoint();
            break;
        case 2:
            // d(-1,0,0), h(1,0,0)
            line[0] = vertex[1].toPoint();
            line[1] = vertex[2].toPoint();
            break;
        case 3:
            // d(0,-1,0), h(0,1,0)
            line[0] = vertex[2].toPoint();
            line[1] = vertex[0].toPoint();
            break;
        case 4:
            // e(0,-1,1), e(0,1,-1)
            line[0] = vertex[0].toPoint();
            line[1] = intersection( vertex[1], vertex[2] );
            break;
        case 5:
            // e(-1,0,1), e(1,0,-1)
            line[0] = vertex[1].toPoint();
            line[1] = intersection( vertex[2], vertex[0] );
            break;
        case 6:
            // e(-1,1,0), e(1,0,-1)
            line[0] = vertex[2].toPoint();
            line[1] = intersection( vertex[0], vertex[1] );
            break;
        case 7:
            // c(-1,1,-1), f(1,1,-1)
            line[0] = intersection( vertex[0], vertex[1] );
            line[1] = intersection( vertex[1], vertex[2] );
            break;
        case 8:
            // c(-1,-1,1), f(1,1,-1)
            line[0] = intersection( vertex[1], vertex[2] );
            line[1] = intersection( vertex[2], vertex[0] );
            break;
        case 9:
            // f(-1,1,1), c(1,-1,-1)
            line[0] = intersection( vertex[2], vertex[0] );
            line[1] = intersection( vertex[0], vertex[1] );
            break;
        case 10:
            // g(0,0,0)
            // The CONREC algorithm has no satisfying solution for
            // what to do, when all vertices are on the plane.

            if ( ignoreOnPlane )
                found = false;
            else
            {
                line[0] = vertex[2].toPoint();
                line[1] = vertex[0].toPoint();
            }
            break;
        default:
            found = false;
    }

    return found;
}

inline int QwtRasterData::ContourPlane::compare( double z ) const
{
    if ( z > d_z )
        return 1;

    if ( z < d_z )
        return -1;

    return 0;
}

inline QPointF QwtRasterData::ContourPlane::intersection(
    const QwtPoint3D& p1, const QwtPoint3D &p2 ) const
{
    const double h1 = p1.z() - d_z;
    const double h2 = p2.z() - d_z;

    const double x = ( h2 * p1.x() - h1 * p2.x() ) / ( h2 - h1 );
    const double y = ( h2 * p1.y() - h1 * p2.y() ) / ( h2 - h1 );

    return QPointF( x, y );
}

class QwtRasterData::PrivateData
{
public:
    QwtRasterData::Attributes attributes;
};  

QwtRasterData::QwtRasterData()
{
    d_data = new PrivateData();
}

QwtRasterData::~QwtRasterData()
{
    delete d_data;
}

void QwtRasterData::setAttribute( Attribute attribute, bool on )
{
    if ( on )
        d_data->attributes |= attribute;
    else
        d_data->attributes &= ~attribute;
}

bool QwtRasterData::testAttribute( Attribute attribute ) const
{
    return d_data->attributes & attribute;
}

void QwtRasterData::initRaster( const QRectF &area, const QSize &raster )
{
    Q_UNUSED( area );
    Q_UNUSED( raster );
}

void QwtRasterData::discardRaster()
{
}

QRectF QwtRasterData::pixelHint( const QRectF &area ) const
{
    Q_UNUSED( area );
    return QRectF(); 
}

QwtRasterData::ContourLines QwtRasterData::contourLines(
    const QRectF &rect, const QSize &raster,
    const QList<double> &levels, ConrecFlags flags ) const
{
    ContourLines contourLines;

    if ( levels.size() == 0 || !rect.isValid() || !raster.isValid() )
        return contourLines;

    const double dx = rect.width() / raster.width();
    const double dy = rect.height() / raster.height();

    const bool ignoreOnPlane =
        flags & QwtRasterData::IgnoreAllVerticesOnLevel;

    const QwtInterval range = interval( Qt::ZAxis );
    bool ignoreOutOfRange = false;
    if ( range.isValid() )
        ignoreOutOfRange = flags & IgnoreOutOfRange;

    QwtRasterData *that = const_cast<QwtRasterData *>( this );
    that->initRaster( rect, raster );

    for ( int y = 0; y < raster.height() - 1; y++ )
    {
        enum Position
        {
            Center,

            TopLeft,
            TopRight,
            BottomRight,
            BottomLeft,

            NumPositions
        };

        QwtPoint3D xy[NumPositions];

        for ( int x = 0; x < raster.width() - 1; x++ )
        {
            const QPointF pos( rect.x() + x * dx, rect.y() + y * dy );

            if ( x == 0 )
            {
                xy[TopRight].setX( pos.x() );
                xy[TopRight].setY( pos.y() );
                xy[TopRight].setZ(
                    value( xy[TopRight].x(), xy[TopRight].y() )
                );

                xy[BottomRight].setX( pos.x() );
                xy[BottomRight].setY( pos.y() + dy );
                xy[BottomRight].setZ(
                    value( xy[BottomRight].x(), xy[BottomRight].y() )
                );
            }

            xy[TopLeft] = xy[TopRight];
            xy[BottomLeft] = xy[BottomRight];

            xy[TopRight].setX( pos.x() + dx );
            xy[TopRight].setY( pos.y() );
            xy[BottomRight].setX( pos.x() + dx );
            xy[BottomRight].setY( pos.y() + dy );

            xy[TopRight].setZ(
                value( xy[TopRight].x(), xy[TopRight].y() )
            );
            xy[BottomRight].setZ(
                value( xy[BottomRight].x(), xy[BottomRight].y() )
            );

            double zMin = xy[TopLeft].z();
            double zMax = zMin;
            double zSum = zMin;

            for ( int i = TopRight; i <= BottomLeft; i++ )
            {
                const double z = xy[i].z();

                zSum += z;
                if ( z < zMin )
                    zMin = z;
                if ( z > zMax )
                    zMax = z;
            }

            if ( qIsNaN( zSum ) )
            {
                // one of the points is NaN
                continue;
            }

            if ( ignoreOutOfRange )
            {
                if ( !range.contains( zMin ) || !range.contains( zMax ) )
                    continue;
            }

            if ( zMax < levels[0] ||
                zMin > levels[levels.size() - 1] )
            {
                continue;
            }

            xy[Center].setX( pos.x() + 0.5 * dx );
            xy[Center].setY( pos.y() + 0.5 * dy );
            xy[Center].setZ( 0.25 * zSum );

            const int numLevels = levels.size();
            for ( int l = 0; l < numLevels; l++ )
            {
                const double level = levels[l];
                if ( level < zMin || level > zMax )
                    continue;
                QPolygonF &lines = contourLines[level];
                const ContourPlane plane( level );

                QPointF line[2];
                QwtPoint3D vertex[3];

                for ( int m = TopLeft; m < NumPositions; m++ )
                {
                    vertex[0] = xy[m];
                    vertex[1] = xy[0];
                    vertex[2] = xy[m != BottomLeft ? m + 1 : TopLeft];

                    const bool intersects =
                        plane.intersect( vertex, line, ignoreOnPlane );
                    if ( intersects )
                    {
                        lines += line[0];
                        lines += line[1];
                    }
                }
            }
        }
    }

    that->discardRaster();

    return contourLines;
}