What is the writing background of Hui Chong Riverside Night Scene?

Night Scene by Huichong River is a poem written by Su Shi, a writer in Song Dynasty, for Hui Chong. The night view of the Hui Chong River was written in A.D. 1085. At that time, Su Shi and his friend Hui Chong met in Bianjing, and wrote two poems for two paintings by Hui Chong, Night Scene by the River. Su Shi (1037-11year), born in Meizhou (now Meishan, Sichuan), was a writer, calligrapher and painter in the Northern Song Dynasty. With his father Su Xun and his brother Su Zhe, they are also called "Three Sus".