2012

Table Of Contents
manufacturers under the Photometric Web panel in the Properties palette for
the light. The light icon represents the photometric web you select.
A light that uses a photometric web can be added to a drawing by entering
the commands WEBLIGHT and FREEWEB at the command prompt. The
WEBLIGHT command creates a targeted weblight, whereas the FREEWEB
command creates a weblight without an explicit target.
To describe the directional distribution of the light emitted by a source,
AutoCAD approximates the source by a point light placed at its photometric
center. With this approximation, the distribution is characterized as a function
of the outgoing direction only. The luminous intensity of the source for a
predetermined set of horizontal and vertical angles is provided, and the system
can compute the luminous intensity along an arbitrary direction by
interpolation.
NOTE Web distribution is used only in rendered images. Weblights are
approximated as point lights in the viewport.
NOTE You can control the size of a web glyph from Tools menu > Options >
Drafting > Light Glyph Settings. Some web glyphs may appear very small on screen
and may need to be adjusted.
Goniometric Diagrams
Photometric data is often depicted using a goniometric diagram.
Goniometric diagram of a web distribution
2166 | Chapter 44 Add Lighting to Your Model