(1.5um face amount bvh eg), (1.8um face amount bvh eg), confirmed by the grain boundary (2.5um face amount bvh eg) ③ ② conditions conditions conditions ① results.
Results: condition (1) (Eg of BVH 1.5 um faces), condition (2) (Eg of BVH 1.8 um faces), condition (3) (Eg of BVH 2.5 um faces) grain surface determine.