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Bump mapping adds texture to a 3D surface without increasing polygon count. Three types of bump mapping include basic, normal, and parallax maps. It is useful for creating realistic surfaces in video games with limited polygon counts.
Bump mapping is a process by which a texture, or texture map, is applied to a surface in a three-dimensional (3D) computer graphics program to create more detail on that surface. A bump map is typically used to add a greater amount of dimensionality and surface detail, such as bumps, ridges, scratches, and other details that affect the smoothness of a surface. Using such mapping allows an object created in a computer graphics (CG) program to appear more realistic without increasing the number of polygons in the object. Bump mapping is typically accomplished through the use of traditional bump maps, normal maps, or parallax maps.
When an object is created in a 3D graphics program, it is created using a wireframe to which polygons are applied. This creates the basic shape of the object and gives it a surface. Complicated objects often have more polygons than simple objects, but higher polygon counts often make objects more difficult to render. This isn’t always a concern with CG created for movies, but video games that render images in real time often have limitations on the number of polygons that can be rendered in a given scene.
Bump mapping is typically used to allow objects with lower polygon counts to appear more realistic. For example, a single surface could be used to create a brick wall and would have only one polygon. To make the surface look realistic, each brick should protrude slightly beyond the mortar between them, and they should have some dents, scratches, and other textures. Using bump mapping, these details can be added without increasing the polygon count in the scene.
There are three different types of bump mapping that can be used, although they generally all create somewhat similar effects. A basic bump map uses a grayscale image, using only white, gray, and black, to create a map. When this texture is applied as a bump map, the object will appear to have more texture; white areas will appear raised, while black areas will appear indented. This type of bump mapping doesn’t actually change the surface of the object, just how light and shadow are rendered on that surface to give it the appearance of a texture.
A normal map is a type of map used in bump mapping that uses red, blue, and green to create a similar effect. Normal maps are typically created based on a highly detailed version of an object and then applied to a low detail version of that object to create a more realistic look with fewer polygons. Parallax maps can also be used in bump mapping, although these are a bit more complicated. They basically work by mimicking the parallax effect that occurs when an object is viewed from different points of view, to create the illusion of depth for a surface when viewed from an angle.
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