Graphics Reference
In-Depth Information
Consider the settings for the sun lamp. Sunlight has a yellow
cast, which is generally offset visually by the blue cast of
the illumination from the rest of the sky. Use the color
picker in the lamp's controls to set it to a mild yellow (R,
1.0; G, 0.9; B, 0.6). We'll already be getting a certain
amount of light from the environment, so we should reduce
the sun's energy value a little. Since we're getting 0.5
energy from the environment itself, let's just cut the sun's
energy to the same level so that for things in direct sunlight,
they end up with a 1.0 on light energy (0.5 from AO plus
0.5 from the sun).
At this point you could just turn on the Ray Shadow
button for the sun lamp and call it finished. If you have a
complex scene though, say characters with hair or fur, or
grass or trees with actual leaves, render times with ray
tracing can head through the roof. Also, you probably don't
want to have the completely sharp shadows that ray tracing
produces.
Here's a different technique for using buffered shadows,
which are much more controllable, in conjunction with a
sun lamp. RMB select the sun and duplicate it with Shift-
D. Move the new copy of the sun lamp a little so you can
select it easily without getting confused with the original.
Take a look at
Figure 5.24
, which shows the controls for
this duplicate lamp. In the
Lamp
panel, change it from
Sun
to
Spot
, so that we can use buffered shadows. Then, adjust
the
Size
,
Clip Start
, and
Clip End
values so that the objects just fit inside the cone and clip indicator,
like the demonstration in
Figure 5.20
. Set the buffer controls to the defaults given earlier in the chapter:
Softness: 3
;
Bias: 0.2
;
Size: 2048
;
Samples: 8
. You may need to move the lamp in order to get the
cone and clip area to intersect with the objects in the scene. This is fine, but be sure not to rotate the
lamp. This is because we are trying to match the shadows cast by this lamp with the illumination of the
sun. The angle must be the same as the sun lamp's, but, since the sun lamp isn't location dependent, any
location of a spot lamp will work. If you were to render now, you'd get double illumination—once from
the sun, once from this spot lamp—and only a single shadow.
Figure 5.22
Environment Lighting
settings
for
outdoor lighting baseline.
The key is to disable illumination on the spot lamp, but leave the shadow. On the
Shadow
panel, enable
Only Shadow
. This will cause the lamp to cast a shadow without generating any light. Not “real world”
by any stretch of the imagination, but it's an extremely flexible production technique. Rendering now will
most likely produce an image with no cast shadows. Why not? The spot lamp is possibly far enough away
that its energy (which in this case is shadow energy) isn't strong enough to cast a visible shadow. The sun
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