Autodesk LIGHTSCAPE, Manual

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Glossary
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where light shining from a source partly reaches the
receiving surface and is partly occluded by some
other obstacle in the environment.
photometric web
A regular grid of luminous intensity samples that
describes the luminous intensity distribution of a
light source.
photometry
The measurement of light taking into account the
psychophysical aspects of the human eye/brain per-
ceptual system.
point light
A light source so small compared to its distance from
the observer or receiving surface that its radiation
can be assumed to come from a dimensionless lumi-
nous point.
procedural texture mapping
A more general form of texture mapping that is usu-
ally not based on images and that can affect more
than just the material color.
progressive refinement
A technique for computing radiosity solutions that
starts with the direct illumination and then computes
more and more of the indirect illumination until the
solution converges.
radiosity
A technique for solving the global illumination prob-
lem for diffuse environments.
ray offset
The displacement measured from the origin of a
shadow ray. Intersections between a surface and a
shadow ray closer to the origin than the ray offset
amount are discarded.
ray tracing
A way of computing an image based on tracing paths
of light from the eye back to the luminaires.
reflectance
The ratio of the luminous flux reflected off a surface
to the luminous flux incident on it.
reflection
Light incident on one side of a surface leaving it from
the same side.
reflection model
A description of how light interacts with a surface.
refractive index
Ratio of the speed of light in a vacuum to the speed of
light in a material. Determines the amount of light
reflected and transmitted at the interface between
them.
refraction
The bending of light rays as they pass from one mate-
rial, such as air, into another material, such as glass.
rotate
The rotation of the camera about its center.
saturation (of a color)
One of three parameters in the HSV (Hue, Satura-
tion, Value) color space. It describes how pure the
color is. A color with a low saturation is very close to
gray.
scroll
A camera motion parallel to the screen. In an ortho-
graphic view, the focus point moves with the camera.
In perspective view, the focus point remains the same
but the screen is tilted with respect to the view direc-
tion.
self-emitted luminance
Luminance emitted from a surface that is not due to
reflection of incoming light off that surface.
shadow ray
A line cast between a point on a light source and a
point on a receiving surface to determine the possible
presence of occluders that would prevent light from
the source from reaching the receiving surface.
SI units
International System of Photometric Units.
sky conditions
The conditions of the sky at a given time and loca-
tion; described as the fraction of the sky covered by
clouds or as clear, partly cloudy, or cloudy sky.
skylight
Light energy from the sun that reaches the scene after