Hi I have got a panel which should point onto an entity in my map (showing where the next quest begins). This entity is marked like this:

ENTITY* MyTarget;

action SetMyTarget() {
MyTarget = my;
}

Now I want to change the angle of a panel to point onto this target. Trying this wasn't a success:

Zeiger_panel.center_x = Zeiger_panel.size_x * 0.5;
Zeiger_panel.center_y = Zeiger_panel.size_y * 0.5;
while(1) {

while (MyTarget == null) {wait(1); beep;};
vec_set(temp,myTarget);
vec_sub(temp,player);
vec_to_angle(Zeiger_panel.angle,temp);
wait(1);
}
}

The panels angle didn't change at all Anybody knows why?

panel.angle isn't 3D (pan, tilt, roll)...

It's simply for rotating a panel (like roll)

Yeah I know but the panels angle should be seen as x-rotation (pan?) like a compass pointing onto an entity but on north.

In this case you could use vec_to_screen to transform the entities world coordinates to screen coordinates.
Then you should be able to use vec_diff and vec_to_angle to get the right angle for your panel.