smoothing of the cylinder

例句：

1. 1.The surface of the metal is very smooth.
   金属的表面非常光滑。
2. 2. The car's wheels are perfectly smooth.
   汽车的轮子非常光滑。
3. 3. The painting was made with a smooth brushstroke.
   这幅画是用平滑的笔触完成的。