Autodesk LIGHTSCAPE, Manual

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Glossary
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process of compensation for this nonlinearity.
global illumination
The effect of all possible types of light transport
(direct illumination, indirect illumination) through-
out an environment.
GON file format
See TBT file format .
hue
One of three parameters in the HSV (Hue Saturation
Value) color space. It describes the dominant wave-
length of the color such as red, yellow, or green.
identity transformation
A function that transforms a point to itself. A geo-
metric transformation that has no effect.
IES file format
The standard file format adopted by the Illuminating
Engineering Society for the electronic transfer of
photometric data and related information—used in
North America.
illuminance
The luminous flux incident on a surface of unit area.
Illuminating Engineering Society (IES)
The technical authority for the illumination field in
North America.
indirect illumination
Illumination that results from light reaching a surface
after being reflected by one or more other surfaces in
the environment.
indirect source
A surface that reflects light into the environment and
thus acts as a light source.
initiation
The Lightscape operation that converts the initial
description of a model into data structures suitable
for the radiosity processing.
intensity magnitude
The intensity of a light in photometric units. This
plus a color can be used to determine the radiometric
quantities needed for the simulation.
intensity mapping
A type of procedural texture mapping used to vary
the intensity over a surface to make it appear less per-
fect and more like a real surface.
interlacing
A technique of displaying every other scan line when
updating a video image. First the even scan lines are
displayed, then the odd ones. This allows the entire
screen to be updated only every thirtieth of a second
rather than every sixtieth.
interreflection
The reflection of light between two surfaces in the
environment.
Inventor file format
The file format used by Silicon Graphics Open Inven-
tor to describe the 3D scene.
inverse square law
The law stating that the illuminance measured at a
point on a surface is directly proportional to the
luminous intensity of a point light source in the
direction of the receiving point and inversely propor-
tional to the square of the distance between the
source and the point.
isotropic distribution
A constant luminous intensity distribution.
jittering
A small, random change in a position or direction
used to prevent aliasing artifacts.
lambertian surface
A surface that reflects the same luminance in all
directions. See
diffuse reflection .
lamp
An artificial source of light. Normally used to denote
a light bulb.
level of detail
A technique to improve rendering performance by
eliminating detail from complex objects that only
cover a small area on the screen. Because the object
appears small, any detail is unlikely to be visible any-
way.