Normal mapping

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The use of bump mapping in HL2.

The type of  bump map used in Source is called Dot3 Bump Mapping or simply Normal mapping.

Bump mapping is a technique where at each pixel, a perturbation to the surface normal of the object being rendered is looked up in a texture map and applied before the illumination calculation is done. The result is a richer, more detailed surface representation that more closely resembles the details inherent in the natural world.

Bump mapping has been applied to the brick material to give it an almost 3D effect on the surface and grooves. Models in Source engine can do the same. Bump mapping can be applied to a range of materials such as water and clothing or to add texture to monsters.

Antlions in Half-Life 2 use bump mapping on their shell texture giving them a more natural insect-like appearance.

See also

• Normal Maps
• Normal Map Creation
• Material Creation
•  Bump mapping - a bump mapping article at Wikipedia

Technically, bump mapping is applied to fragments in the fragment processor, not pixels. At the point in the pipeline where bump mapping is applied, they are not quite yet pixels. When they come out of the fragment processor (and bump mapping has already been applied) and get sent to the frame buffers, then they are pixels.