What is the meaning of "three distances" in China's landscape paintings?

High, flat and far. Guo, a painter in the Northern Song Dynasty, summed up his predecessors' painting experience and his own painting practice, and founded the theory of "Three Distances" in theory. It not only summarizes China's perspective treatment of spatial relationship, but also embodies the unique spatial aesthetic consciousness of China painters. The "plain" landscape in Sanyuan is especially favored and valued by painters. In the feelings of literati, the landscape painting of "Plain" contains richer artistic conception.