Bump mapping

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A sphere without bump mapping.

This sphere is geometrically the same as the first, but has a bump map applied. This changes how it reacts to shading, giving it the appearance of a bumpy texture resembling that of an orange.

Bump mapping is a computer graphics technique where at each pixel, a perturbation to the surface normal of the object being rendered is looked up in a heightmap and applied before the illumination calculation is done (see, for instance, Phong shading). The result is a richer, more detailed surface representation that more closely resembles the details inherent in the natural world.

The difference between displacement mapping and bump mapping is evident in the example images; in bump mapping, the normal alone is perturbed, not the geometry itself. This leads to artifacts in the silhoutte of the object (the sphere still has a circular silhoutte).

Fake bump mapping

Programmers of 3D graphics sometimes use computationally cheaper fake bump mapping techniques in order to a simulate bump mapping. One such method uses texel index alteration instead of altering surface normals, often used for '2D' bump mapping. As of GeForce 2 class card this technique is implemented in graphics accelerator hardware.

Full-screen 2D fake bump mapping, which could be easily implemented with a very simple and fast rendering loop, was a very common visual effect in the demos of the 1990's.

References

• Blinn, James F. "Simulation of Wrinkled Surfaces", Computer Graphics, Vol. 12 (3), pp. 286-292 SIGGRAPH-ACM (August 1978)

Links

• http://www.jawed.com/bump/ Real-time bump mapping demo in Java (includes source code)

See also

• Normal mapping
• Parallax mapping
• Displacement mapping

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