void CalcRayDirection()
        {
            Vector3 dir = entity.Velocity;
            Vector3 P   = new Vector3(bb.Min.X, bb.Min.Y, bb.Max.Z);

            tracerP1Y1.SetRayData(P, dir);
            P.Y = bb.Max.Y;
            tracerP1Y1.SetRayData(P, dir);

            P = new Vector3(bb.Max.X, bb.Min.Y, bb.Min.Z);
            tracerP2Y1.SetRayData(P, dir);
            P.Y = bb.Max.Y;
            tracerP2Y2.SetRayData(P, dir);
        }