qt - Rotating a QGraphicsItem and finding the new position of it -


i working on tower defence game , trying shoot projectile turret. sprite of turret have looks this

enter image description here

also, bullet looks enter image description here

what want make turret shot bullet point (for example attackdestination = qpointf(1000, 500);

for this, have class bullet, slot move:

void bullet::move() {      int stepsize = 20; // how fast bullet moves     double angle = rotation();      double dy = stepsize * qsin(qdegreestoradians(angle)); // x needs moved     double dx = stepsize * qcos(qdegreestoradians(angle)); // y needs moved      setpos(x() + dx, y() + dy); }

which triggered qtimer.

i have slot in tower class (which stands turret)

void tower::attacktarget() {     bullet *bullet = new bullet();     //getwidthmap() returns width of tower     //getheightmap() returns height of tower      bullet->setpos(x() + getwidthmap() /2, y());      qlinef line(qpointf(x() + getwidthmap() /2, y()), attackdestination);     double angle =(-1) *  line.angle();      bullet->setrotation(angle);      this->setrotation(90 + angle);      game->scene->additem(bullet);  }

i have rotated turret +90 degrees because initial position vertical , needs form angle (that of line ox) bullet. rotation happens clockwise.

the problem position of bullet relative turret when attacking.

without line this->setrotation(90 + angle); (first picture), (second picture)

enter image description here

enter image description here

as can see, bullets starting initial position of turret (when not rotated), because pos() function keeps initial x , y. how can fix ?


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