When a 3D model is created, 2D images can be overlaid on it to add colors, designs, and textures. This is called mapping, and often the entirety of a model’s color comes from this. These maps can be created in programs like Photoshop, and the illusions of textures can be brushed onto the models as easily as if you painted them yourself; some animators even use real photographs of the textures they’re trying to create, simply captured and then altered to make seamless repeatable patterns. This is how many illusions of hair are created; rather than model individual strands, instead grouped locks of hair are modeled, before a texture is overlaid with individual strands and detailing painted on. This still leaves a flat-looking surface, almost plastic, without any three-dimensional texture. It’s too smooth, too reflective, and doesn’t look anything like the detailed cracks and crevices, hairs and pores that you think of when you think of movie-quality 3D modeling.
Animators do not actually create every last one of those details in minute polygons, matching them perfectly to the patterns of the bitmap textures applied. Instead, a grayscale version of the texture map can be applied in a different way, as a bump map; the rendering engine reads the ranges of grey between white and black as various increasing levels of elevation, and every variation in shade causes a variation in the raised texture of the model’s surface.
When mapping texture and bump maps together, especially if they’re overlaid to precisely match, you can create a convincing illusion of a raised, textured surface that can fool almost any eye. It’s a key part of realistic animation. And now, when looking at any 3D animation, you can study the textures visible on the screen and understand just how they were created.