What are the meanings of "three nins and three noes" mentioned in calligraphy?

"Three Nings and Three No's" is the essence of painting summarized by Mr. Xu Beihong, a master of modern Chinese painting, that is, not round, not dirty and not clever in Ning Zhuo. The so-called "Fang Ning is not round" is expressed by a straight line, that is, the shape is cut out. I believe all the teachers must have taught how to cut the ball when they first learned to draw the ball, so I won't explain it much. Simply put, it is square, straight and fast. To put it simply, it is better to be dirty than clean, that is, to dare to combine lines and faces by rubbing and flanking. One plus one is definitely greater than two. Ning Zhuo's coincidence means painting objectively. I believe many people know the story of painting eggs and carambola. They tell us that every object is different, even an object is different from different angles, so objectivity is often greater than subjectivity, that is, draw whatever you see, don't add or subtract casually, and pay attention to the performance of the painting object. Understand this "Three Nings and Three Don 'ts", and you will know how to quickly master the essentials of sketching and sketching.