2009

Procedure
To create a light from a manufacturer's IES file:
1 Create a Target or Free photometric light.
2 In the General Parameters rollout > Light Distribution (Type) group,
choose Photometric Web File from the Distribution list.
A Distribution (Photometric File) rollout opens on the command panel.
3 In the Distribution (Photometric File) rollout, click the button labelled
Choose Photometric File.
A file selection dialog appears. Choose the IES file that you want to use.
Photometric Webs
A photometric web is a 3D representation of the light intensity distribution
of a light source. This directional light distribution information is stored in a
photometric data file in the IES format using the IES LM-63-1991 standard
file format
on page 5034, or in the LTLI or CIBSE formats for photometric data.
You can load photometric data files provided by various manufacturers as web
parameters. In viewports, the light object changes to the shape of the
photometric web you choose.
To describe the directional distribution of the light emitted by a source, 3ds
Max 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 3ds Max
computes the luminous intensity along an arbitrary direction by interpolation.
Web Diagrams
Photometric data is often depicted using a diagram. Diagrams that show
rotation about an axis are known as goniometric.
5030 | Chapter 18 Lights and Cameras