Architectural_Design_with_SketchUp

Architectural Design with SketchUp
Spotlights
The second light type that any rendering software is capable of handling is spotlights. As
the name implies, these shine light from the source in one direction only, producing a cone
of light that can be used to illuminate details or provide dramatic light scenarios. Real-world
equivalents are recessed lights (potlights) in a house and spotlights on a stage.
To evaluate spotlights, let’s apply some to the same scene that we used in Figure 5.46.
Figure 5.48 shows the result on the left and the setup on the right. The only difference is
the replacement of the three omni lights in Figure 5.46 with spotlights, all pointing down,
in Figure 5.48.
Figure 5.48: Setup with three similar spotlights
This scene already looks good and realistic even without any modifications. The two
spotlights in the back are close to the background and therefore produce nice-looking light
cones on the wall. All three have soft edges and produce soft shadows.
As we did with the omni lights, we can now modify some of the properties of the spotlights.
For example, Figure 5.49 shows what happens when we change the light color of the
two in the back to blue. Together with the spotlight in the front, this immediately produces
very nice stage lighting.
It is usually desirable that spotlights have soft edges. This is likewise rooted in reality
because light cones, even from the most focused stage spots, don’t have perfectly sharp
edges. Nevertheless, let’s explore what happens when we modify the related properties.
Figure 5.50 illustrates what happens when we switch from a soft-edged spot (on the left)
to a hard-edged one (on the right).
The two spotlight properties of importance here are typically called hotspot and falloff,
illustrated in Figure 5.51. Hotspot typically is an angular measure of the central light cone
that will have 100% light intensity. Falloff describes the outer cone (again, as a value describing
the “opening” angle) where light reduces in intensity from 100% strength to zero (at its
outermost edge).
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