i didnt check your code yet but here is the cos sin one:

int camera_distance = 40;

camera.x = player.x - camera_distance * cos(camera.pan);
camera.y = player.y - camera_distance * sin(camera.pan);
camera.z = player.z + camera_distance*0.8;

but i still prefer the vectory one. be ware if your fps is higher your camera turns faster with the code above.


edit: it didnt flickered for me.