在我的游戏中,我想从火箭发射器发射火箭。玩家将火箭发射器作为儿童物品。火箭必须是无父的。我正试图定位火箭,使其背部与火箭发射器的后部对齐(玩家在屏幕截图中朝向北方)并在其中水平居中:
相反,我得到的是:
旋转也不正确(运行示例并移动鼠标光标以查看我的意思)。我的代码在哪里出错?
#include <QtWidgets>
QPointF moveBy(const QPointF &pos, qreal rotation, float distance)
{
return pos - QTransform().rotate(rotation).map(QPointF(0, distance));
}
float directionTo(const QPointF &source, const QPointF &target) {
QPointF toTarget(target.x() - source.x(), target.y() - source.y());
float facingTarget = qRadiansToDegrees(atan2(toTarget.y(), toTarget.x())) + 90.0f;
facingTarget = fmod(facingTarget, 360.0f);
if(facingTarget < 0)
facingTarget += 360.0f;
return facingTarget;
}
class Controller : public QObject
{
public:
Controller(QGraphicsScene *scene) :
mScene(scene)
{
mPlayer = scene->addRect(0, 0, 25, 25, QPen(Qt::blue));
mPlayer->setTransformOriginPoint(mPlayer->boundingRect().width() / 2, mPlayer->boundingRect().height() / 2);
mRocketLauncher = scene->addRect(0, 0, 16, 40, QPen(Qt::green));
mRocketLauncher->setParentItem(mPlayer);
mRocketLauncher->setPos(mPlayer->boundingRect().width() * 0.9 - mRocketLauncher->boundingRect().width() / 2,
-mRocketLauncher->boundingRect().height() * 0.3);
mRocket = scene->addRect(0, 0, 16, 20, QPen(Qt::red));
scene->installEventFilter(this);
QGraphicsTextItem *playerText = scene->addText("Player");
playerText->setPos(0, 100);
playerText->setDefaultTextColor(Qt::blue);
QGraphicsTextItem *rocketLauncherText = scene->addText("Rocket launcher");
rocketLauncherText->setPos(0, 120);
rocketLauncherText->setDefaultTextColor(Qt::green);
QGraphicsTextItem *rocketText = scene->addText("Rocket");
rocketText->setPos(0, 140);
rocketText->setDefaultTextColor(Qt::red);
}
bool eventFilter(QObject *, QEvent *event) {
if (event->type() == QEvent::GraphicsSceneMouseMove) {
const QGraphicsSceneMouseEvent *mouseEvent = static_cast<QGraphicsSceneMouseEvent*>(event);
mPlayer->setRotation(directionTo(mPlayer->sceneBoundingRect().center(), mouseEvent->scenePos()));
qreal rocketX = mRocketLauncher->sceneBoundingRect().center().x() - mRocket->boundingRect().width() / 2;
QPointF rocketPos(rocketX, 0);
rocketPos = moveBy(rocketPos, mPlayer->rotation(), mRocketLauncher->boundingRect().height() - mRocket->boundingRect().height());
mRocket->setPos(rocketPos);
mRocket->setRotation(mPlayer->rotation());
return true;
}
return false;
}
private:
QGraphicsScene *mScene;
QGraphicsRectItem *mPlayer;
QGraphicsRectItem *mRocketLauncher;
QGraphicsRectItem *mRocket;
};
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QGraphicsView view;
view.setMouseTracking(true);
QGraphicsScene *scene = new QGraphicsScene;
view.setScene(scene);
Controller controller(scene);
view.resize(300, 300);
view.show();
return app.exec();
}
答案 0 :(得分:1)
这个想法是:
代码:
mPlayer->setRotation(directionTo(mPlayer->sceneBoundingRect().center(),
mouseEvent->scenePos()));
mRocket->setRotation(mPlayer->rotation());
QPointF launcherPos = mRocketLauncher->mapToScene(
mRocketLauncher->boundingRect().bottomLeft());
QPointF currentRocketPos = mRocket->mapToScene(
mRocket->boundingRect().bottomLeft());
mRocket->setPos(mRocket->pos() - currentRocketPos + launcherPos);