500
AutoCAD and Its Applications—Advanced
Copyright Goodheart-Willcox Co., Inc.
Point Lights
Point lights are user-created lights that have light rays projecting in all directions.
See Figure 17-12. When a point light is created, its location must be specifi ed. Since
point lights illuminate in all directions, there is no “to” location for a point light. A
light glyph represents point lights in the drawing. See Figure 17-13. Point lights can be
set to attenuate. In this case, the distance of the objects in the scene to the point light
affects the intensity of the illumination.
The
POINTLIGHT
or
LIGHT
command is used to create a point light. You are fi rst
prompted to specify the location of the point light. Once the location is established, several
options for the light are available. You can name the light, set the intensity, turn the light on
or off, adjust the photometry settings, determine if and how shadows are cast, set the atten-
uation, and set the light color. The Name,
Intensity
(or
Intensity
Factor), Status, Photometry,
Shadow, and
Color
(or
Filter
Color) options work the same as the corresponding options for
a distant light. However, additional photometry settings are available when photometric
lighting is active. The
Intensity
option provides additional options for setting the power
of the light source. The
Flux
option can be used to specify the power in lumens (lm). The
Illuminance
option can be used to specify the illuminance in lux (lx) or foot-candles (fc),
depending on the current lighting units. An additional option, Distance, is available under
Illuminance. This defaults to one unit and is used to calculate illuminance.
The
Attenuation
option is used to set attenuation for the point light when photo-
metric lighting is off. When this option is selected, fi ve more options are available:
•
Attenuation Type
•
Use Limits
•
Attenuation Start Limit
•
Attenuation End Limit
•
Exit
The
Exit
option returns you to the previous prompt.
POINTLIGHT
Ribbon
Visualize
Lights
Point
Type
POINTLIGHT
LIGHT
A B
Figure 17-12.
A—A point light is placed inside of the lamp fixture. Notice how the light projects in all
directions. B—When shadow casting is turned on for the light, the lampshade blocks the
light from illuminating objects below the shade.
Figure 17-13.
This is the light
glyph for a point
light.