raycasting.cpp Example File

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 #include <QtCore>
 #include <QtWidgets>

 #include <math.h>

 #ifndef M_PI
 #define M_PI 3.14159265358979323846
 #endif

 #define WORLD_SIZE 8
 int world_map[WORLD_SIZE][WORLD_SIZE] = {
     { 1, 1, 1, 1, 6, 1, 1, 1 },
     { 1, 0, 0, 1, 0, 0, 0, 7 },
     { 1, 1, 0, 1, 0, 1, 1, 1 },
     { 6, 0, 0, 0, 0, 0, 0, 3 },
     { 1, 8, 8, 0, 8, 0, 8, 1 },
     { 2, 2, 0, 0, 8, 8, 7, 1 },
     { 3, 0, 0, 0, 0, 0, 0, 5 },
     { 2, 2, 2, 2, 7, 4, 4, 4 },
 };

 #define TEXTURE_SIZE 64
 #define TEXTURE_BLOCK (TEXTURE_SIZE * TEXTURE_SIZE)

 class Raycasting: public QWidget
 {
 public:
     Raycasting(QWidget *parent = 0)
             : QWidget(parent)
             , angle(0.5)
             , playerPos(1.5, 1.5)
             , angleDelta(0)
             , moveDelta(0)
             , touchDevice(false) {

         // http://www.areyep.com/RIPandMCS-TextureLibrary.html
         textureImg.load(":/textures.png");
         textureImg = textureImg.convertToFormat(QImage::Format_ARGB32);
         Q_ASSERT(textureImg.width() == TEXTURE_SIZE * 2);
         Q_ASSERT(textureImg.bytesPerLine() == 4 * TEXTURE_SIZE * 2);
         textureCount = textureImg.height() / TEXTURE_SIZE;

         watch.start();
         ticker.start(25, this);
         setAttribute(Qt::WA_OpaquePaintEvent, true);
         setMouseTracking(false);
     }

     void updatePlayer() {
         int interval = qBound(20, watch.elapsed(), 250);
         watch.start();
         angle += angleDelta * interval / 1000;
         qreal step = moveDelta * interval / 1000;
         qreal dx = cos(angle) * step;
         qreal dy = sin(angle) * step;
         QPointF pos = playerPos + 3 * QPointF(dx, dy);
         int xi = static_cast<int>(pos.x());
         int yi = static_cast<int>(pos.y());
         if (world_map[yi][xi] == 0)
             playerPos = playerPos + QPointF(dx, dy);
     }

     void showFps() {
         static QTime frameTick;
         static int totalFrame = 0;
         if (!(totalFrame & 31)) {
             int elapsed = frameTick.elapsed();
             frameTick.start();
             int fps = 32 * 1000 / (1 + elapsed);
             setWindowTitle(QString("Raycasting (%1 FPS)").arg(fps));
         }
         totalFrame++;
     }

     void render() {

         // setup the screen surface
         if (buffer.size() != bufferSize)
             buffer = QImage(bufferSize, QImage::Format_ARGB32);
         int bufw = buffer.width();
         int bufh = buffer.height();
         if (bufw <= 0 || bufh <= 0)
             return;

         // we intentionally cheat here, to avoid detach
         const uchar *ptr = buffer.bits();
         QRgb *start = (QRgb*)(ptr);
         QRgb stride = buffer.bytesPerLine() / 4;
         QRgb *finish = start + stride * bufh;

         // prepare the texture pointer
         const uchar *src = textureImg.bits();
         const QRgb *texsrc = reinterpret_cast<const QRgb*>(src);

         // cast all rays here
         qreal sina = sin(angle);
         qreal cosa = cos(angle);
         qreal u = cosa - sina;
         qreal v = sina + cosa;
         qreal du = 2 * sina / bufw;
         qreal dv = -2 * cosa / bufw;

         for (int ray = 0; ray < bufw; ++ray, u += du, v += dv) {
             // every time this ray advances 'u' units in x direction,
             // it also advanced 'v' units in y direction
             qreal uu = (u < 0) ? -u : u;
             qreal vv = (v < 0) ? -v : v;
             qreal duu = 1 / uu;
             qreal dvv = 1 / vv;
             int stepx = (u < 0) ? -1 : 1;
             int stepy = (v < 0) ? -1 : 1;

             // the cell in the map that we need to check
             qreal px = playerPos.x();
             qreal py = playerPos.y();
             int mapx = static_cast<int>(px);
             int mapy = static_cast<int>(py);

             // the position and texture for the hit
             int texture = 0;
             qreal hitdist = 0.1;
             qreal texofs = 0;
             bool dark = false;

             // first hit at constant x and constant y lines
             qreal distx = (u > 0) ? (mapx + 1 - px) * duu : (px - mapx) * duu;
             qreal disty = (v > 0) ? (mapy + 1 - py) * dvv : (py - mapy) * dvv;

             // loop until we hit something
             while (texture <= 0) {
                 if (distx > disty) {
                     // shorter distance to a hit in constant y line
                     hitdist = disty;
                     disty += dvv;
                     mapy += stepy;
                     texture = world_map[mapy][mapx];
                     if (texture > 0) {
                         dark = true;
                         if (stepy > 0) {
                             qreal ofs = px + u * (mapy - py) / v;
                             texofs = ofs - floor(ofs);
                         } else {
                             qreal ofs = px + u * (mapy + 1 - py) / v;
                             texofs = ofs - floor(ofs);
                         }
                     }
                 } else {
                     // shorter distance to a hit in constant x line
                     hitdist = distx;
                     distx += duu;
                     mapx += stepx;
                     texture = world_map[mapy][mapx];
                     if (texture > 0) {
                         if (stepx > 0) {
                             qreal ofs = py + v * (mapx - px) / u;
                             texofs = ofs - floor(ofs);
                         } else {
                             qreal ofs = py + v * (mapx + 1 - px) / u;
                             texofs = ceil(ofs) - ofs;
                         }
                     }
                 }
             }

             // get the texture, note that the texture image
             // has two textures horizontally, "normal" vs "dark"
             int col = static_cast<int>(texofs * TEXTURE_SIZE);
             col = qBound(0, col, TEXTURE_SIZE - 1);
             texture = (texture - 1) % textureCount;
             const QRgb *tex = texsrc + TEXTURE_BLOCK * texture * 2 +
                               (TEXTURE_SIZE * 2 * col);
             if (dark)
                 tex += TEXTURE_SIZE;

             // start from the texture center (horizontally)
             int h = static_cast<int>(bufw / hitdist / 2);
             int dy = (TEXTURE_SIZE << 12) / h;
             int p1 = ((TEXTURE_SIZE / 2) << 12) - dy;
             int p2 = p1 + dy;

             // start from the screen center (vertically)
             // y1 will go up (decrease), y2 will go down (increase)
             int y1 = bufh / 2;
             int y2 = y1 + 1;
             QRgb *pixel1 = start + y1 * stride + ray;
             QRgb *pixel2 = pixel1 + stride;

             // map the texture to the sliver
             while (y1 >= 0 && y2 < bufh && p1 >= 0) {
                 *pixel1 = tex[p1 >> 12];
                 *pixel2 = tex[p2 >> 12];
                 p1 -= dy;
                 p2 += dy;
                 --y1;
                 ++y2;
                 pixel1 -= stride;
                 pixel2 += stride;
             }

             // ceiling and floor
             for (; pixel1 > start; pixel1 -= stride)
                 *pixel1 = qRgb(0, 0, 0);
             for (; pixel2 < finish; pixel2 += stride)
                 *pixel2 = qRgb(96, 96, 96);
         }

         update(QRect(QPoint(0, 0), bufferSize));
     }

 protected:

     void resizeEvent(QResizeEvent*) {
 #if defined(Q_OS_WINCE_WM)
         touchDevice = true;
 #else
         touchDevice = false;
 #endif
         if (touchDevice) {
             if (width() < height()) {
                 trackPad = QRect(0, height() / 2, width(), height() / 2);
                 centerPad = QPoint(width() / 2, height() * 3 / 4);
                 bufferSize = QSize(width(), height() / 2);
             } else {
                 trackPad = QRect(width() / 2, 0, width() / 2, height());
                 centerPad = QPoint(width() * 3 / 4, height() / 2);
                 bufferSize = QSize(width() / 2, height());
             }
         } else {
             trackPad = QRect();
             bufferSize = size();
         }
         update();
    }

     void timerEvent(QTimerEvent*) {
         updatePlayer();
         render();
         showFps();
     }

     void paintEvent(QPaintEvent *event) {
         QPainter p(this);
         p.setCompositionMode(QPainter::CompositionMode_Source);

         p.drawImage(event->rect(), buffer, event->rect());

         if (touchDevice && event->rect().intersects(trackPad)) {
             p.fillRect(trackPad, Qt::white);
             p.setPen(QPen(QColor(224, 224, 224), 6));
             int rad = qMin(trackPad.width(), trackPad.height()) * 0.3;
             p.drawEllipse(centerPad, rad, rad);

             p.setPen(Qt::NoPen);
             p.setBrush(Qt::gray);

             QPolygon poly;
             poly << QPoint(-30, 0);
             poly << QPoint(0, -40);
             poly << QPoint(30, 0);

             p.translate(centerPad);
             for (int i = 0; i < 4; ++i) {
                 p.rotate(90);
                 p.translate(0, 20 - rad);
                 p.drawPolygon(poly);
                 p.translate(0, rad - 20);
             }
         }

         p.end();
     }

     void keyPressEvent(QKeyEvent *event) {
         event->accept();
         if (event->key() == Qt::Key_Left)
             angleDelta = 1.3 * M_PI;
         if (event->key() == Qt::Key_Right)
             angleDelta = -1.3 * M_PI;
         if (event->key() == Qt::Key_Up)
             moveDelta = 2.5;
         if (event->key() == Qt::Key_Down)
             moveDelta = -2.5;
     }

     void keyReleaseEvent(QKeyEvent *event) {
         event->accept();
         if (event->key() == Qt::Key_Left)
             angleDelta = (angleDelta > 0) ? 0 : angleDelta;
         if (event->key() == Qt::Key_Right)
             angleDelta = (angleDelta < 0) ? 0 : angleDelta;
         if (event->key() == Qt::Key_Up)
             moveDelta = (moveDelta > 0) ? 0 : moveDelta;
         if (event->key() == Qt::Key_Down)
             moveDelta = (moveDelta < 0) ? 0 : moveDelta;
     }

     void mousePressEvent(QMouseEvent *event) {
         qreal dx = centerPad.x() - event->pos().x();
         qreal dy = centerPad.y() - event->pos().y();
         angleDelta = dx * 2 * M_PI / width();
         moveDelta = dy * 10 / height();
     }

     void mouseMoveEvent(QMouseEvent *event) {
         qreal dx = centerPad.x() - event->pos().x();
         qreal dy = centerPad.y() - event->pos().y();
         angleDelta = dx * 2 * M_PI / width();
         moveDelta = dy * 10 / height();
     }

     void mouseReleaseEvent(QMouseEvent*) {
         angleDelta = 0;
         moveDelta = 0;
     }

 private:
     QTime watch;
     QBasicTimer ticker;
     QImage buffer;
     qreal angle;
     QPointF playerPos;
     qreal angleDelta;
     qreal moveDelta;
     QImage textureImg;
     int textureCount;
     bool touchDevice;
     QRect trackPad;
     QPoint centerPad;
     QSize bufferSize;
 };

 int main(int argc, char **argv)
 {
     QApplication app(argc, argv);

     Raycasting w;
     w.setWindowTitle("Raycasting");
     w.resize(640, 480);
     w.show();

     return app.exec();
 }