Global Illumination Options
Have you ever stopped to look around you? Take your face out of this book or away from the computer for a moment, and just look around. Whether you're at your desk, in your living room, or outside, everything has global lighting properties. You can control these global properties—global light intensity, global lens flare intensity, ambient intensity, ambient color, radiosity, and caustics—on the Global Illumination tab of the Render Globals panel. To open it, click the Render tab at the top of the Layout interface, and then click the Render Globals tool button. The Global Illumination settings are found in the Global Illum tab, among the five settings tabs at the top of the panel (Figure 4.8).
Figure 4.8 The Global Illumination control tab, found in the Render Globals panel, governs such properties as global light intensity, global lens flare intensity, radiosity, and caustics.
Global Light and Lens Flare Intensity
In the Global Illumination panel, click the Render tab at the bottom of the panel. At the bottom of the panel is a (light) Intensity value, currently set at 100%. Because it's in the Render Globals panel, it globally changes the intensity on all lights in your scene. This can be useful for scenes that have multiple lights that need to become brighter or dimmer over time.
Let's say you're animating a stage play or musical concert, for example. You have 29 spotlights shining on the stage, the players, and the actors. All their intensities are randomly and quickly changing to the beat of the music, and perhaps focusing on key performers. At the end of the song, you want all the lights to fade out equally. Instead of setting the light intensity 29 times for each light, which you could do through the Scene Editor, it is better to ramp down the Global Light Intensity setting. Similarly, if you have lens flares applied to these lights, you can globally change the Flare Intensity setting for lights, just below the Intensity setting.
Radiosity and Caustics
Also within the Global Illumination panel (within the Render Globals panel) are the Enable Radiosity and Enable Caustics settings. These two features in LightWave enable you to take your 3D creations even further by adding more real-world lighting properties.
Radiosity is a rendering solution that calculates the diffused reflections of lights in a scene. It is the rate at which light energy leaves a surface. This also includes the color within all surfaces. In simpler terms, radiosity is bounced light. A single light coming through a window, for example, can light up an entire room. The light hits the surfaces of the objects and bounces, lighting up the rest of the room, in turn creating a realistic image. Ambient light is often considered a poor man's radiosity. You can use ambient light to brighten areas not directly lit by lights.
You'll use radiosity and learn more about its settings in Chapter 8, "3D Product Shots."
Caustics are created when light is reflected off a surface or through a refracted surface. A good example is the random pattern often seen at the bottom of a swimming pool when bright sunlight shines through the water. Another example is the dapples of light that appear on floors or ceilings when light glints off a crystal vase or a gold-plated statue.