zài / sù miáo kè shàng / lǎo shī / xiān / yòng / jiǎn dān de / fāng hé zi / jiǎng jiě / tòu shì huà fǎ

在素描课上，老师先用简单的方盒子讲解透视画法。

In the sketching class, the teacher first used a simple box to explain perspective drawing.