The
scene has one distant lightsource, which
is pointing towards the table and ambient
intensity is at 25% (Lightwave’s
default value). Note that the road is
too dark, the legs of the table are
too bright, the chairs and the stool
are too dark. The cloth and the box
on the table are too bright. The problem
is here is not the intensity of the
light coming in from the distant light,
it is the diffusion values that I have
set for the objects in the scene. No
matter how you adjust the intensity
of the light or its angle, if you do
not set the diffusion values of your
surfaces properly, you will always end
up with such disparities.
In
Fig.13 below, I have reduced the diffusion
values of those objects that were
too bright, and increased the values
of those that were too dim. I have
also increased the light intensity
from 100% to 170%.
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Fig.13
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Note
that some parts of the image are still
dark and some are still bright. I am
talking about the two chairs in the
scene. The one farther from the camera
is brighter than the one closer to the
camera. But both of them have the same
surface! We have hit another problem
and that is of the angle of the chairs
relative to the light. We have used
a distant light source up till now.
Either we can add another light slightly
displaced from the position of the light
present in the scene, or we can use
area lights. If we add another distant
light and displace it slightly, it might
fix the disparities in the brightness
of objects in the scene, but it will
lead to two shadows for all objects.
That is not how it is, at least on this
planet. Even with the single distant
light, the shadows are unrealistically
sharp. Replacing the distant light with
a distant shadow-mapped spotlight will
not solve the problem entirely. While
the shadows will become soft, their
softness will not vary as the shadows
moves away from their parent objects
(If the shadows are not playing a major
part in the picture, then one should
use shadow-mapped lights instead of
area lights).
Until
now I have not really applied what
I have discussed in the previous sections.
Now it is time…to get real. I
will replace now replace our primary
distant light source with an area
light placed far into the ‘sky’,
reduce the ambient intensity to 0%
(like it is in the real world), and
add some fill lights to the scene
to simulate bounced light from the
surroundings.
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Fig.
14
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In
Fig. 14 above, the sun simulating light
source is an area light source with
a small area. The settings for the light
are as follows.
Light
Type: Area
Intensity:
90%
Color:
Red—252, Green—201, Blue—143
Shadow
Type: Ray Trace
No
Diffusion: Off
No
Specular: Off
Fig.
15 and Fig. 16 show a close-up view
of the scene and descriptions about
other fill lights in the scene.
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Fig.
15 (left View)
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Fig.
16 (Top View)
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The
Reflected Floor Light has been placed
just below the ground. This has been
done to simulate the reflected light
from the ground and to serve as a fill
light. The settings for the light are
given below.
Light
Type: Point
Intensity:
30%
Color:
Red—255, Green—225, Blue—198
Shadow
Type: Off
No
Diffusion: Off
No
Specular: On (box checked)
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Settings
for the light labeled ‘Fill Light’
are given below.
Light
Type: Distant
Intensity:
35%
Color:
Red—255, Green—225, Blue—198
Shadow
Type: Off
No
Diffusion: Off
No
Specular: On (box checked)
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Again,
the purpose of this light is to fill
up dark areas and make them a bit
brighter.
Settings
for the light labeled ‘Reflected
light from surroundings on the right’
are given below.
Light
Type: Area
Intensity:
47%
Color:
Red—255, Green—225, Blue—198
Shadow
Type: On
No
Diffusion: Off
No
Specular: On (box checked)
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Note
that this light has shadows turned on
and its long and narrow in size. This
size was made this was to simulate light
that is reflected off say a wall on
the right of the table, not visible
to the camera. The shadows have been
turned on for this fill light in particular
because area lights tend to produce
much realistic shadows and in our case,
the light produces an extremely soft
shadow for the stool. Now you can say
that an area light source will push
the rendering time upward and turning
on the shadows will have the same effect.
Well, you are right in saying that.
But when I replaced the light with a
distant light with shadows turned off,
the scene hardly looked realistic. Consider
the figure below and see how the stool
casts no shadows onto the floor that
lies within the shadow of the table.
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Fig.
17
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With
the long and narrow area light with
shadows turned on, the resulting image
came out to be much better looking.
(Fig. 18)
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Fig.
18
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With
this done, we are ready for the final
render. However, we are not done yet.
I have noticed that sometimes Lightwave
tends to over-saturate colors, especially
when using light intensities beyond
100%. To fix this, I sometimes take
my Lightwave renders into PhotoShop
and reduce the color saturation. I also
increase the contrast of my images to
counter Lightwave’s linear light
fall-off. (there are plugins available
that let you adjust hue/saturation/brightness/contrast
etc. from withing Lightwave) And if
my image looks too clean, I sometimes
tend to add some noise into my images.
Before
concluding this article, I would like
to remind you again about diffusion
settings. If you can’t get it
right by playing around with light
settings, play around with the diffusion
settings. Diffusion settings have
a strong impact on the realism value
of the scene, and should never be
taken lightly.
So
go out in the sunlight…and just
observe, but carefully…and you
shall become themaster of natural
lighting.
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