Architectural_Design_with_SketchUp

Chapter 5 Rendering in SketchUp
If you are curious about what IES light data looks like, open an IES file with a text editor. You
will see several lines of text describing the light fixture and the manufacturer. Below that
are several numbers that simply describe (in 2D) the light distribution—in other words,
the location of the yellow points in Figure 5.52. Your rendering software can use this to
reproduce the light distribution accurately in 3D space when you use IES lights in your scene.
TIP
Once you have the IES file you want to use, go into your rendering software and start
applying it to a spotlight. Because the IES light data is directional (it can have uplight as well
as downlight properties), you must make sure the orientation (rotation and tilt) of the light
is appropriate. Figure 5.53 shows how IES data is applied and visualized using the Twilight
rendering software in SketchUp.
Figure 5.53: Applying IES light data to a spotlight
Once you render your scene, you should see the light distribution that was provided by
the IES file (it should look less uniform than a standard spotlight). If the light intensity is not as
needed, you will need to modify that property. Also, you can usually add a color to the IES light,
if desired. It may be necessary to adjust light attenuation to even out light distribution as well.
Figure 5.54 shows the standard scene that we have been using throughout this chapter—this
time, illuminated with IES lights. It is interesting to note that the IES data for the
lights on the right indicates a vertical cutoff (it does not contain any data above the light
source), which leads to the horizontal line between light and dark. I should also mention that
if you applied IES data that describes an uplight (e.g., a wall sconce) to a downward-pointing
spotlight, the spotlight will only emit light upward.
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