A sphere without bump mapping.

The bump map that is applied to the image below.

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. An orange —specifically the sweet orange —is the Citrus fruit Citrus sinensis ( syn

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). Computer graphics are Graphics created by Computers and more generally the Representation and Manipulation of Pictorial Data In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image Rendering is the process of generating an image from a model, by means of computer programs In Computer graphics, a heightmap or heightfield is a raster image used to store values such as surface Elevation data for display in Phong shading refers to a set of techniques in 3D computer graphics. 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. In 3D computer graphics, normal mapping is an application of the technique known as Bump mapping. Parallax mapping (also called offset mapping or virtual displacement mapping) is an enhancement of the Bump mapping or Normal mapping techniques

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. Displacement mapping is an alternative computer graphics technique in contrast to Bump mapping, Normal mapping, and Parallax mapping, using a ( procedural This leads to artifacts in the silhouette of the object (the sphere still has a circular silhouette).

Fake bump mapping

Programmers of 3D graphics sometimes use computationally cheaper fake bump mapping techniques in order to simulate bump mapping. A programmer is someone who writes Computer software. The term computer programmer can refer to a specialist in one area of computer programming or to a generalist 3D computer graphics (in contrast to 2D computer graphics) are graphics that use a three-dimensional representation of geometric data that is stored in the computer One such method uses texel index alteration instead of altering surface normals, often used for '2D' bump mapping. A texel, or tex ture el ement (also tex ture pi' xel) is the fundamental unit of texture space used in Computer graphics As of GeForce 2 class card this technique is implemented in graphics accelerator hardware. The GeForce2 ( codenamed NV15) was the second generation of GeForce Graphics cards by Nvidia Corporation.

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, when bump-mapping was first introduced. Demo effects are computer-based real-time Visual effects found in demos created by the Demoscene. A demo is a non-interactive multimedia presentation made within the computer Subculture known as the Demoscene.

Real bump mapping

Real bump mapping makes use of calculating slope for each pixel determining the height map. This can be as little as two lines of code for calculating the X and Y gradient at every pixel or it can be more complex; the final result is that of calculating the slope, so code complexity may not matter. Next a code is made to have these vector point calculations aligned with the U and V axis of the bump map it came from on the normal for the normal to be adjusted correctly. Then the typical lighting transforms the normal’s U and V texture pixel shade by comparing the vector direction point in the map with the light’s normal X, Y and Z point calculation, it then changes per light pixel in the light's rasterization. If the point is more at the light, then it’s brighter, the points facing further away from the light actually get darker more quickly.

If low resolution lights are used like a low pixel non-filtered specular from an earlier shader model, you can see how it works up close, looking like a sweep of animation.

On a normal map instead of false vectors calculated per-pixel through small coding it's stored as a certain color in the map. In 3D computer graphics, normal mapping is an application of the technique known as Bump mapping. Then the same happens on the light's point and X and Y span. Height mapping doesn't replace the normal and builds upon fake ones from the gradient calculations. Height mapping is told to not contain real information in every pixel, it relies on its neighbors. Normal mapping is usually told to contain information in each pixel to where a pixel may cost an operation or more, a reason cards carry many operations.

In some cases real bump mapping can cost less than emboss bump mapping because of the number of passes and amount of texture layers required to produce it; emboss bump mapping uses 2 to 3 extra passes or 3 other units, while real bump mapping can be done in one extra pass or texture layer. Also, it costs less than normal mapping, as normal mapping usually needs more than one pass due to its multi-channel structure, as well as the fact it calculates it much differently.

Environment Mapped Bump Mapping

Matrox G400 Tech Demo with EMBM

The Matrox G400 chip supports, in hardware, a texture-based surface detailing method called Environment Mapped Bump Mapping (EMBM). The G400 is a video card made by Matrox, released in September 1999 It was originally developed by BitBoys Oy and licensed to Matrox. Bitboys Oy is a hardware development and licensing company based in Finland, founded in 1991 and acquired by ATI Technologies for up to US$ 44M EMBM was first introduced in DirectX 6. 0.

The Radeon 7200 also includes hardware support for EMBM, which was demonstrated in the tech demo "Radeon's Ark". The Radeon R100 is the first generation of Radeon graphics chips from ATI Technologies. However, EMBM was not supported by other graphics chips such as NVIDIA's GeForce 256 through GeForce 2, which only supported the simpler Dot-3 BM. The multinational NVIDIA Corporation ( (ɪnˈvɪdiə specializes in the manufacture of graphics-processor technologies for Workstations The GeForce 256 was the first of Nvidia 's " GeForce " product-line The GeForce2 ( codenamed NV15) was the second generation of GeForce Graphics cards by Nvidia Corporation. Due to this lack of industry-wide support, and its toll on the limited graphics hardware of the time, EMBM only saw limited use during G400's time. Only a few games supported the feature, such as Dungeon Keeper 2 and Millennium Soldier: Expendable. Dungeon Keeper 2 is an IBM PC Strategy game developed by Bullfrog Productions and published by Electronic Arts in 1999| Millennium Soldier Expendable (known as Expendable in the USA and Seitai Heiki Expendable in Japan is the title of a Shoot 'em up

EMBM initially required specialized hardware within the chip for its calculations, such as the Matrox G400 or Radeon 7200. It could also be rendered by the programmable pixel shaders of later DirectX 8. 0 accelerators like the GeForce 3 and Radeon 8500. The GeForce3 ( Codenamed NV20) was Nvidia 's third-generation GeForce chip The Radeon R200 is the second generation of Radeon graphics chips from ATI Technologies. More recent games supporting EMBM include Doom 3 and Far Cry. Doom 3 is a Science fiction Survival horror Video game developed by Id Software and published by Activision. Far Cry is a First-person shooter Video game developed by Crytek Studios from Germany and published by Ubisoft

Requirements

Bump mapping has been implemented in modern graphics hardware going back to the late 1990s in such systems as Nvidia GeForce cards, ATI Radeon cards, Microsoft Xbox series, Sony Playstation 2, Sega Dreamcast, and Nintendo GameCube.

It is useful to note that software implementaitons of bump-mapping effects, such as simple 'emboss' mapping, have been around for over a decade. Almost any system can accomplish this technique--the speed of the rendering, however, can vary widely.

References

• Blinn, James F. "Simulation of Wrinkled Surfaces", Computer Graphics, Vol. 12 (3), pp. 286-292 SIGGRAPH-ACM (August 1978)
• Hoejengaard, Rasmus, Rasmus Højengaard Interview in Play Magazine, as translated at http://www.hitmanforum.com/show.php?id=28819&catid=36

See also

• Texture mapping
• Normal mapping
• Parallax mapping
• Displacement mapping
• Relief Texture Mapping

External links

• 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)