Camera movement

move.cpp

// z movement
void camera::advance(const float distance) {
  this->position += (this->viewDir * -distance);
}

// y movement
void camera::ascend(const float distance) {
  this->position += (this->upVector * distance);
}

// x movement
void camera::strafe(const float distance) {
  this->position += (this->rightVector * distance);
}