The taboo of sketch is impetuousness, which is an attitude problem. If you want to learn sketch well, you must first be clear! In addition, you should observe more and think more: the gypsum cube we see is different from that painted on paper. Because of space, the plaster can only be seen on three sides at most, so you can't even see the bottom. You can't see the back when you see the front; The object you look at is at an angle to your line of sight. This is a perspective problem in sketch. Read a good book. Objects in space are displayed on a plane and must be changed. Don't draw squares. That's wrong! Give you a few ideas: first, the spatial position relationship; Second, perspective contraction (angle and inclination are related to the shape in space); Third, according to your picture, how big is it? Moderate size, small painting, empty painting, large painting, too full top; Fourth, molding, determine the dividing line between light and dark, which is the bright surface? Which is the dark side? Layer by layer, this is a process of continuous consolidation and improvement. You have to think carefully and think carefully, so don't take it seriously.