1. First draw the shape of crayfish with 2B pencil, and pay attention to the dynamic relationship of crayfish. Then draw the dark part of crayfish with 2B pencil, and also draw the dark part of claws.

2. Continue to deepen the dark part with 4B pencil, draw the surface texture with short strokes, and deepen the connection between the legs and the body; Draw the top color of the head with 2B pencil, this part should be brighter, pay attention to the change of surface lines, and leave the highlights blank; Just decorate the part of the dragon beard meat.

Operational definition of sketch: the drawing method of expressing objects with a relatively single color with the help of lightness change. Sketch painting tools are varied and not limited to one tool. Sketch is a relatively fast sketch form. Sketch level is one of the important indicators reflecting the basic level of painting and basic modeling ability of painters.

Sketch is an important foundation of realistic painting, and it is also the art of restraint that needs rational assistance most. Generally speaking, beginners learn to sketch first, and those who sketch well will naturally draw well in oil painting. The origin of sketch generally began in the Renaissance. In fact, Greek bottle paintings and sculptures have a good sketch foundation.

The original sketch is considered as a manuscript of painting. For example, to make a mural, we must first have a draft of the idea, then a draft of the sketch, and at the same time, we must have an accurate sketch of the hand and face. Painting murals is used to not looking at the model, relying entirely on the sketches prepared in advance and the painter's memory.