Rain-drop wrinkle texture: similar to the modeling concept of Cow-hair wrinkle texture, but the particles deposited by Rain-drop wrinkle texture are more symmetrical and regular in shape, and the particle groups are in a state of aggregation, dispersion and non-uniform random distribution. In addition, we can also control the length of the rain spots and the sharpness of the head and tail linearly. The Rain-drop wrinkle texture only needs the change of ink color, not the texture, and the final effect is shown in Figure 13.