A gonioreflectometer is a device for measuring a

bidirectional reflectance distribution function The bidirectional reflectance distribution function (BRDF; f_(\omega_,\, \omega_) ) is a function of four real variables that defines how light is reflected at an opaque surface. It is employed in the optics of real-world light, in compute ...

(BRDF). The device consists of a light source illuminating the material to be measured and a sensor that captures light reflected from that material. The light source should be able to

illuminate Illuminate may refer to: Music Bands * Illuminate (2009), a 2009 E.P. by English Progressive Metal band Suns of the Tundra * Illuminate (band), a German gothic music band Albums and EPs * ''Illuminate'' (Joe Morris and Rob Brown album), 1995 ...

and the sensor should be able to capture data from a

hemisphere Hemisphere refers to: * A half of a sphere As half of the Earth * A hemisphere of Earth ** Northern Hemisphere ** Southern Hemisphere ** Eastern Hemisphere ** Western Hemisphere ** Land and water hemispheres * A half of the (geocentric) celes ...

around the target. The hemispherical rotation

dimension In physics and mathematics, the dimension of a mathematical space (or object) is informally defined as the minimum number of coordinates needed to specify any point within it. Thus, a line has a dimension of one (1D) because only one coor ...

s of the sensor and light source are the four dimensions of the BRDF. The 'gonio' part of the word refers to the device's ability to measure at different angles. Several similar devices have been built and used to capture data for similar functions. Most of these devices use a

camera A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with a ...

instead of the light intensity-measuring sensor to capture a two-dimensional sample of the target. Examples include: *a spatial gonioreflectometer for capturing the SBRDF{{What, date=April 2011 (McAllister, 2002). *a camera gantry for capturing the

light field The light field is a vector function that describes the amount of light flowing in every direction through every point in space. The space of all possible '' light rays'' is given by the five-dimensional plenoptic function, and the magnitude of e ...

(Levoy and Hanrahan, 1996). *an unnamed device for capturing the

bidirectional texture function Bidirectional texture function (BTF) is a 6-dimensional function depending on planar texture coordinates (x,y) as well as on view and illumination spherical angles. In practice this function is obtained as a set of several thousand color images of ...

(Dana et al., 1999).

References

*Dana, Kristin et al. 1999. ''Reflectance and Texture of Real-World Surfaces''. in

ACM Transactions on Graphics ''ACM Transactions on Graphics'' (TOG) is a bimonthly peer-reviewed scientific journal that covers the field of computer graphics. It was established in 1982 and is published by the Association for Computing Machinery. TOG publishes two special iss ...

. Volume 18, Issue 1 (January, 1999). New York, NY, USA: ACM Press. Pages 1-34. *Foo, Sing Choong. 1997. ''A Gonioreflectometer for measuring the bidirectional reflectance of materials for use in illumination computations''. Masters thesis.

Cornell University Cornell University is a private statutory land-grant research university based in Ithaca, New York. It is a member of the Ivy League. Founded in 1865 by Ezra Cornell and Andrew Dickson White, Cornell was founded with the intention to tea ...

. Ithaca, New York, USA. *Levoy, Marc & Hanrahan, Pat. 1996. '' Light field rendering''. In Proceedings of the 23rd annual conference on Computer graphics and interactive techniques. *McAllister, David. 2002. ''A Generalized Surface Appearance Representation for Computer Graphics''. PhD dissertation.

University of North Carolina at Chapel Hill A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States ...

, Department of Computer Science. Chapel Hill, USA. 118p. Computer graphics Photometry Measuring instruments