Specularity is the visual appearance of

specular reflection Specular reflection, or regular reflection, is the mirror-like reflection (physics), reflection of waves, such as light, from a surface. The law of reflection states that a reflected ray (optics), ray of light emerges from the reflecting surf ...

In computer graphics

computer graphics Computer graphics deals with generating images and art with the aid of computers. Computer graphics is a core technology in digital photography, film, video games, digital art, cell phone and computer displays, and many specialized applications. ...

, it means the quantity used in three-dimensional (3D) rendering which represents the amount of

reflectivity The reflectance of the surface of a material is its effectiveness in Reflection (physics), reflecting radiant energy. It is the fraction of incident electromagnetic power that is reflected at the boundary. Reflectance is a component of the respon ...

a surface has. It is a key component in determining the

brightness Brightness is an attribute of visual perception in which a source appears to be radiating/reflecting light. In other words, brightness is the perception dictated by the luminance of a visual target. The perception is not linear to luminance, and ...

of specular highlights, along with shininess to determine the size of the highlights. It is frequently used in

real-time computer graphics Real-time computer graphics or real-time rendering is the sub-field of computer graphics focused on producing and analyzing images in real time. The term can refer to anything from rendering an application's graphical user interface ( GUI) to ...

and ray tracing, where the mirror-like specular reflection of

light Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...

from other surfaces is often ignored (due to the more intensive computations required to calculate it), and the specular reflection of light directly from point light sources is modeled as specular highlights.

Specular mapping

A materials system may allow specularity to vary across a surface, controlled by additional layers of

texture maps Texture may refer to: Science and technology * Image texture, the spatial arrangement of color or intensities in an image * Surface texture, the smoothness, roughness, or bumpiness of the surface of an object * Texture (roads), road surface c ...

The early misinterpretation of "Specularity" in computer graphics

Early shaders included a parameter called "Specularity". CG Artists, confused by this term discovered by experimentation that the manipulation of this parameter would cause a reflected highlight from a light source to appear and disappear and therefore misinterpreted "specularity" to mean "light highlights". In fact "Specular" is defined in optics as ''Optics. (of reflected light) directed, as from a smooth, polished surface (opposed to

diffuse Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical p ...

).'' A specular surface is a highly smooth surface. When the surface is very smooth, the reflected highlight is easy to see. As the surface becomes rougher, the reflected highlights gets broader and dimmer. This is a more "diffused" reflection.

In seismology

In the context of

seismic migration Seismic migration is the process by which seismic events are geometrically re-located in either space or time to the location the event occurred in the subsurface rather than the location that it was recorded at the surface, thereby creating a more ...

, specularity is defined as the cosine of the angle made by the

surface normal In geometry, a normal is an object (e.g. a line, ray, or vector) that is perpendicular to a given object. For example, the normal line to a plane curve at a given point is the infinite straight line perpendicular to the tangent line to the ...

vector and the

angle bisector In geometry, bisection is the division of something into two equal or congruent parts (having the same shape and size). Usually it involves a bisecting line, also called a ''bisector''. The most often considered types of bisectors are the ''se ...

of the angle defined by the directions of the incident and diffracted rays. For a purely specular seismic event the value of specularity should be equal to unity, as the angle between the surface normal vector and the angle bisector should be zero, according to Snell's Law. For a diffractive seismic event, the specularity can be sub-unitary. During the seismic migration, one can filter each seismic event according to the value of specularity, in order to enhance the contribution of

diffraction Diffraction is the deviation of waves from straight-line propagation without any change in their energy due to an obstacle or through an aperture. The diffracting object or aperture effectively becomes a secondary source of the Wave propagation ...

s in the seismic image. Alternatively, the events can be separated in different sub-images according to the value of specularity to produce a specularity gather.

References

3D computer graphics Geophysics {{Compu-graphics-stub

In computer graphics

Specular mapping

The early misinterpretation of "Specularity" in computer graphics

In seismology

See also

References