Interior, Radiosity
Naturally, there are few lighting effects in
LightWave that look as good as radiosity. Let’s
apply some to our kitchen scene and see what
the net lighting effect is, and then we’ll see if
we can simulate that radiosity using other
tricks.
First, open up your Render Globals panel
and click on the Global Illum tab. Once that tab
is open, click Enable Radiosity and set the
radiosity type to Interpolated.
Now simply hit the F9 button to create a
test render.
Part III: Creating Lighting ··································
520
Figure 26.63
Figure 26.64
There are several problems with this render. First, it took over two
hours to render a single frame with Enhanced Low radiosity. Second, the
image is grainy and of poor quality. We could fix the grain by increasing
the Rays Per Evaluation setting, but the render time is already out of
control. So instead, we’ll solve both of these problems by turning off
radiosity and using a few tricks to simulate the radiosity bounces. So go
ahead and disable radiosity in your Global Illum tab.
Now, the trick is to add bounce lights wherever we think there
should be a radiosity bounce. The purists will argue that every surface in
the room produces a radiosity bounce, and that is technically correct.
What we are interested in, however, is where the most apparent
bounces will occur so that we can place lights there of the right color,
shape, and intensity to simulate the radiosity bounce. To LightWave, this
is just another light, so there will be no deadly radiosity calculations tak
-
ing up your wee hours.
When I look at our kitchen scene with the two fluorescent tubes
beneath the cabinets, I imagine that the most obvious place for a bounce
light source is on the counter beneath the cabinets, directly under the
bright light sources. I could use any light type I wish, but I know that a
radiosity bounce is diffused, causing soft shadows. I also know that
most radiosity bounces take place over a wide area. Therefore,
····························Chapter 26: Lighting Setup Examples
521
Figure 26.65
I’m going to select area lights as our bounce lights. If this technique
requires too much render time, we can always retreat to a spotlight if
necessary, but that wouldn’t be my first choice.
I’ll place a pair of rectangular area lights facing upward just above
the countertop, right beneath the fluorescent sources.
Although you can’t tell from the black and white image, the countertops
are green. Any bounce light will obey the laws of physics. The colored
bounce surface will absorb most of the light wavelengths except those
that are the color of the surface, in this case green. Our bounce lights
should therefore be green.
Subtlety is the key with fake radiosity bounces. Set the lights’ inten
-
sity fairly low, maybe around 20% to 25%. Turn on Linear falloff. Check
the falloff Range/Nominal Distance to be sure that the light will reach
the immediately surrounding geometry but not too much farther.
Adding two area lights to our scene only increased the render by a
couple of minutes because they were fairly small. Remember, the larger
the area light, the longer the render time.
Part III: Creating Lighting ··································
522
Figure 26.66

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.