gistfile1.txt

    /** Represents abstract environment for objects that inside */
    struct IMoveEnvironment
    {
        /** Converts relative object position that environment contains into global position
            Takes 'outGlobal' parameter as local object position offset and converts it into global position */
        virtual void ComputeGlobalPosition(Vector3& outGlobal) = 0;

        /** Converts global into relative object position */
        virtual void ComputeLocalPosition(Vector3& outLocal) = 0;
    };

    struct MovingEntity0
    {
        IMoveEnvironment* m_Environment;

        /** Relative position */
        Vector3 Position;

        explicit MovingEntity0() : m_Environment(nullptr) {}

        /** Attaches entity to environment.
            Null environment can be passed also. In this case entity will be attached to global coordinate system.
            Note: environment switch does not changes global position. */
        void Environment(IMoveEnvironment* Env)
        {
            if (Env == m_Environment)
                return;

            Position = GlobalPosition();    // "move" our entity into global coord system
            if (Env == nullptr)
                ;   // special case: null environment recognized as global coordinate system, nothing to do
            else
                Env->ComputeLocalPosition(Position);    // convert global into relative position
            m_Environment = Env;
        }

        /** Current environment entity attached.
            In case environment is null - it means that entity attached to global coordinate system. */
        IMoveEnvironment* Environment() const {
            return m_Environment;
        }

        Vector3 GlobalPosition() const
        {
            Vector3 global(Position);
            if (m_Environment != nullptr)
                m_Environment->ComputeGlobalPosition(global);
            return global;
        }
    }