Bump mapping
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. Normal mapping is the most commonly used bump mapping technique, but there are other alternatives, such as Parallax mapping.
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 silhouette of the object (the sphere still has a circular silhouette).
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Fake bump mapping
Programmers of 3D graphics sometimes use computationally cheaper fake bump mapping techniques in order to 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)
See also
External links
- http://www.jawed.com/bump/ Real-time bump mapping demo in Java (includes source code)
- http://www.blacksmith-studios.dk/projects/downloads/bumpmapping_using_cg.php Bump Mapping tutorial using CG and C++
- http://freespace.virgin.net/hugo.elias/graphics/x_polybm.htm (shows a simple creating vectors per pixel of a grayscale for a bump map to work and more)
Categories
3D computer graphics | Demo effects | Virtual reality