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

3D computer graphics | Demo effects

Bumpmapping | Bump mapping | Placage de relief | Mapowanie wypukłości