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From 2D to 3D: Using Textures to Create Raised Surfaces

From Adrien-Luc Sanders

Three-dimensional models can possess amazing levels of detail; not only in sculpted shapes, but also in texture. Skin surfaces; tree barks; pebbled hides; rusted metal--down to every last pore, every wood scraping, every crack, every pitted surface. It could take a lifetime to actually model every last detail of that by hand; in truth, what you're looking at isn't clever modeling, but an illusion of texturing.

What Exactly is Texturing?
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.

That's Too Easy. Is This All There is to Texturing?
No, not yet. 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. Do you think that the animators actually create every last one of those details in minute polygons, matching them perfectly to the patterns of the bitmap textures applied?

Not hardly. 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. It's kind of like those toys with the blunt-tipped nails or pins set into a plastic plate, where you press your palm or objects into one side of the nails and watch an impression of it rise from the other side as the nails extend by various heights. The principle isn't exactly the same, but the visual outcome is similar.