What is the meaning of 'realm without yi risk' in Chinese painting?

Literally, Yi Danger (彝险) explains razor-sharp. A smooth and easy situation and a perilous adversity.

Situation without Yi risk, refers to the national painting, can not be no danger, can not be no smooth (smooth and slow place)

National painting landscape painting chapter of the theory of the twelve taboos:

Twelve taboos: Yuan Rao nature said: a taboo arrangement pat dense, the second taboo is not divided into near and far, the third taboo mountain without air veins, the four taboos water without source of flow, the five taboos situation without Yi risk, the six taboos road without access, the seven taboos stone only one side, the eight taboos Tree less than four branches, nine taboo characters hunchbacked, ten taboo building mixed, eleven taboo swell and light out of place, twelve taboo dyeing can not be.