9

964 Glossary
Lof ti ng
Acircleisloftedalongapathtoconstructatubularshape.
Loftingisanimportantmethodfor3Dobject
creation. You create shape objects to serve as a
path and any number of cross-sectional shapes.
Thepathbecomestheframeworkthatholdsthe
cross-sections forming your loft object.
Once you create a loft object you can change and
animate its parameters and sub-objec ts:
• Add and replace cross-section shapes or replace
the path.
• Changeoranimatetheparametersofthepath
and shapes.
• Change or animate the surface parameters of
the loft object.
The lofting process first requires that you
create shape objects to serve as the path and
cross-sections of your loft object.
Thetermloftingcomesfromearlyshipbuilding.A
large framework called a loft was built to hold the
hull of a ship while it was assembled. The process
of hoisting the ribs (cross-sections) of the hull into
the loft became know n as lofting.
Atraditionalmethodforbuilding
three-dimensional models of a modern
vehicle design is to draw cross-sect ions at a
number of key p oints. These cross-sections are
cut out to form two-dimensional templates that
arethenplacedonarail.Themodelbuildersfill
in the space between the templates to generate the
surface of the model.
You create loft objects using a similar process. You
first create two or more spline objects. One of these
splines w ill b e the rail, w hich is referred to as the
path. The rest of the splines are the cross-sections
of your object, which are called shapes. As you
arrange your shapes along the path, the s oftware
generates a surface between the shapes.
Log File (mental ray Renderer)
The log file (.log) is an ASCII text file that contains
messages generated by the mental ray renderer.
You specify a name and location for the log file, and
the "verbosity" level of the messages it contains, in
the mental ray prefere nces (page 3–837).
Look At Obj ect
In the context of the Shape Facing operator (page
2–176), a Look At object is the camera or object
toward which particles face.
LTLI Files
The LTLI file t ype is the file format for photometric
data created by t he Danish Illuminating
Laboratory. It is used primari ly in Scandinavian
countries.
Lumi na nce
Luminance is the value of light reflected off a
surface. It is a measure of how brigh t or dark we
perceive the surface.