If you want to exclude all objects, or all but one, you can click on the
dark gray bar in the Exclude window to access the Select All, Clear All,
or Invert Selection options. This is very handy when you have many
items in the scene to select or deselect.
Ambient Intensity
Found at the top of the Light Properties
panel are the Ambient Color and Ambient
Intensity settings. Ambient intensity is the
oft-maligned bastard child of CG lighting.
Most experienced CG artists will automati
-
cally set Ambient Intensity to 0. Simply put,
ambient intensity adds a perfectly even
amount of diffuse illumination to all surfaces
in the scene. The problem with this is that it
is extremely unnatural because it is much
too perfect and therefore is a dead giveaway
that your work is computer generated.
Take heart, though. Ambient intensity is
still a good tool and has recently been given
an entirely new and very crucial importance
in LightWave’s world thanks to the addition
of radiosity.
Part II: LightWave’s Lighting Tools ······························
162
Figure 11.22: The Ambient
Intensity setting.
Figure 11.21: Exclude options.
The biggest advantage to ambient intensity is that it is dirt-cheap to
render. Also, it is somewhat reminiscent of fill light. Sometimes you can
get away with using only ambient intensity as your fill source which is
very good, considering that ambient intensity is the proverbial hare
compared to an area light’s or radiosity’s tortoise. I actually find ambient
intensity most useful for seeing what I am doing in Layout. Oftentimes,
even if I am not using ambient intensity in the shot, I will have it turned
up to illuminate the OpenGL interface, and then I’ll turn it off for the
render. But there are a few instances where ambient intensity can save
the day, most notably when using radiosity. With radiosity, ambient
intensity only adds light to areas that are not already directly lit, which
simulates higher order radiosity bounces. Cool, huh?
The following are remarks by Arnie Cachelin about using ambient
intensity with LightWave’s radiosity. The full text can be found in Ken
-
neth Woodruff’s document “LightWave’s ‘Full Precision’ Renderer and
You,” which is included in the appendix:
“When Radiosity is enabled, the ambient light value is added only to
the indirect diffuse lighting of surfaces, not to the direct lighting.
This means that the ambient level functions as the sum of all the
higher order diffuse light ‘bounces.’ This little-known solution pro-
vides adjustable levels of higher-order lighting, which is generally a
very subtle effect, while avoiding the exponential increase in the
number of expensive ray-trace operations otherwise required by
multi-bounce global illumination solutions. Contrary to your well-
honed instinct for LightWave photo-realism, ambient intensity
should NOT automatically be set to negligible levels for radiosity. In
general, the ambient level will need to account for second and
higher-order bounces from many directions. These bounces will
tend to contribute more if there are very bright lights in the scene,
or bright luminous objects or bright spots in HDR ImageWorld envi
-
ronments. In these cases, bumping up the ambient intensity will
increase accuracy. It will also help smooth noisy artifacts of under
-
sampling, and light nooks and crannies which may otherwise not
sample enough of the environment. This is better than just a hack,
because every level of bounce makes the lighting less directional, of
far lower intensity, and more susceptible to undersampling. Sub
-
suming these bounces into a uniform level takes advantage of these
characteristics, and eliminates the extra sampling requirements.”
····························Chapter 11: General Light Properties
163
What this comes down to is that using ambient intensity with radiosity is
not merely a good thing, it is highly desirable, especially as one of the
main problems with radiosity is the graininess produced by under
-
sampling. Try it out. I think it will give you a new respect for ambient
intensity.
...
This chapter has covered numerous capabilities of the lighting tools
available in LightWave. By now you should have a good grasp of most
of the tools discussed herein. No doubt there are dozens more that I
haven’t thought of, and probably thousands more invented by other art
-
ists in times of need. Use your creativity to find new, effective, and
cheap ways to use these great tools.
Part II: LightWave’s Lighting Tools ······························
164

Get LightWave v9 Lighting (w/CD) now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.