NormalMapping

From Odwiki

Normal Mapping is the process of assigning normals based on a texture map. This is similar to BumpMapping, but allows more complex displacements to be represented because the displacement is not assumed to be along to the Normal direction vector as is the case with Bump Mapping. This allows you to store complex displacement detail in a map and use low resolution models. This has especially large application to realtime rendering (like games), but this be very useful for avoiding the recompuation of highly complex displacement shading too. There is good use for repetitive rendering tasks, like in the lighting phase of production where fast feedback is essential.

You can extract Normal Maps in Mantra using ShaderUnwrapping.