lighting.cpp Example File

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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 */)
  {
  }