Autodesk LIGHTSCAPE, Manual

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Glossary
328
Lightscape
CIBSE file format
The standard file format adopted by the Chartered
Institution of Building Services Engineers for the
electronic transfer of luminaire photometric data—
used in Great Britain.
color
The sensation produced by light entering the eye and
being perceived by the brain.
color matching
The process of mixing a set of colored lights to create
a color that appears exactly like a test color.
color space
A representation for color. All colors are defined with
respect to some particular color space—typically
HSV and RGB.
contrast
The relative difference in illumination between two
adjacent regions.
criterion rating
The fraction of the area of a surface that satisfies or
exceeds a specific criterion.
culling
Lightscape provides control over backface culling,
which discards from the display all surfaces that face
away from the viewer. View frustum culling, which is
always performed when rendering the model,
quickly discards all surfaces totally outside the field
of view (view frustum).
daylight
Availability of the luminous flux from the sun and
sky for a given time, location, and sky conditions.
diffuse distribution
An axially symmetric luminous intensity distribu-
tion such that the emitted light varies as the cosine of
the emission angle, measured from the axis of the
distribution.
diffuse reflection
Incident light reflected by a surface so that the
reflected luminance is the same in all directions.
direct illumination
Illumination resulting from light reaching a surface
directly from a direct light source.
direct source
A light source.
dolly
A camera motion toward or away from the focus
point.
double-buffer
A rendering technique to provide smooth interactive
display. Lightscape renders into the hidden “back”
buffer while displaying the “front” buffer. When fin-
ished, the buffers are instantly swapped so that the
back buffer becomes the (visible) front buffer. If only
Single Buffer is used, Lightscape renders each poly-
gon directly to the screen, resulting in a “flicker”
effect.
DXF file format
The file format standard used by Autodesk’s
AutoCAD package for exchange of drawing data
among CAD applications. Currently the de facto
industry standard.
dynamic range
The ratio of the highest intensity in an image or envi-
ronment to the lowest intensity. The dynamic range
of real scenes is very large. The dynamic range that
most display devices are capable of reproducing is
low.
field angle
The angle of the spotlight aim axis at which the lumi-
nous intensity drops to 0. See
spotlight distribution .
filter
A device that changes the spectral composition of
light transmitted through it.
footcandle (fc)
The AS unit of illuminance, equal to 1 lumen per
square foot.
form factor
The fraction of the energy leaving a light source that
actually arrives at a receiving surface.
gamma
The nonlinear change in light intensity caused by a
particular display device. Gamma is often used as the