- Qt 5.5
- Qt Widgets
- Lighting Effect Example
- lighting.cpp Example File
- Qt 5.5.1 Reference Documentation

# lighting.cpp Example File

effects/lighting/lighting.cpp

    /****************************************************************************
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    ** Copyright (C) 2015 The Qt Company Ltd.
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    ** This file is part of the examples of the Qt Toolkit.
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    ** $QT_BEGIN_LICENSE:BSD$
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    #include "lighting.h"

    #include <QtWidgets>
    #include <QtCore/qmath.h>

    #ifndef M_PI
    #define M_PI 3.14159265358979323846
    #endif

    Lighting::Lighting(QWidget *parent): QGraphicsView(parent), angle(0.0)
    {
        setScene(&m_scene);

        setupScene();

        QTimer *timer = new QTimer(this);
        connect(timer, SIGNAL(timeout()), SLOT(animate()));
        timer->setInterval(30);
        timer->start();

        setRenderHint(QPainter::Antialiasing, true);
        setFrameStyle(QFrame::NoFrame);
    }

    void Lighting::setupScene()
    {
        m_scene.setSceneRect(-300, -200, 600, 460);

        QLinearGradient linearGrad(QPointF(-100, -100), QPointF(100, 100));
        linearGrad.setColorAt(0, QColor(255, 255, 255));
        linearGrad.setColorAt(1, QColor(192, 192, 255));
        setBackgroundBrush(linearGrad);

        QRadialGradient radialGrad(30, 30, 30);
        radialGrad.setColorAt(0, Qt::yellow);
        radialGrad.setColorAt(0.2, Qt::yellow);
        radialGrad.setColorAt(1, Qt::transparent);
        QPixmap pixmap(60, 60);
        pixmap.fill(Qt::transparent);
        QPainter painter(&pixmap);
        painter.setPen(Qt::NoPen);
        painter.setBrush(radialGrad);
        painter.drawEllipse(0, 0, 60, 60);
        painter.end();

        m_lightSource = m_scene.addPixmap(pixmap);
        m_lightSource->setZValue(2);

        for (int i = -2; i < 3; ++i)
            for (int j = -2; j < 3; ++j) {
                QAbstractGraphicsShapeItem *item;
                if ((i + j) & 1)
                    item = new QGraphicsEllipseItem(0, 0, 50, 50);
                else
                    item = new QGraphicsRectItem(0, 0, 50, 50);

                item->setPen(QPen(Qt::black, 1));
                item->setBrush(QBrush(Qt::white));
                QGraphicsDropShadowEffect *effect = new QGraphicsDropShadowEffect;
                effect->setBlurRadius(8);
                item->setGraphicsEffect(effect);
                item->setZValue(1);
                item->setPos(i * 80, j * 80);
                m_scene.addItem(item);
                m_items << item;
            }

    }

    void Lighting::animate()
    {
        angle += (M_PI / 30);
        qreal xs = 200 * qSin(angle) - 40 + 25;
        qreal ys = 200 * qCos(angle) - 40 + 25;
        m_lightSource->setPos(xs, ys);

        for (int i = 0; i < m_items.size(); ++i) {
            QGraphicsItem *item = m_items.at(i);
            Q_ASSERT(item);
            QGraphicsDropShadowEffect *effect = static_cast<QGraphicsDropShadowEffect *>(item->graphicsEffect());
            Q_ASSERT(effect);

            QPointF delta(item->x() - xs, item->y() - ys);
            effect->setOffset(delta.toPoint() / 30);

            qreal dx = delta.x();
            qreal dy = delta.y();
            qreal dd = qSqrt(dx * dx + dy * dy);
            QColor color = effect->color();
            color.setAlphaF(qBound(0.4, 1 - dd / 200.0, 0.7));
            effect->setColor(color);
        }

        m_scene.update();
    }

    void Lighting::resizeEvent(QResizeEvent * /* event */)
    {
    }