[Figure 8-39] Atmosphere root shader

ADD ATMOSPHERE EFFECTS
If you look in the Object List found at the top of the Shader Window in the Material Room, you’ll find an Atmosphere option directly below the Background option. Selecting this option opens the Atmosphere root node in the Advanced panel of the Shader Window, as shown in Figure 8-39. Using this node, you can add depth cue and volume atmospheric effects to the rendered scene.

Enabling atmosphere effects can add a substantial amount of time to the rendering process.

Enabling Depth Cueing
By selecting the Depth Cue option in the root Atmosphere node, you can turn on the depth cueing atmospheric effect. This works just like the Depth Cue option in the Document Window by making objects farther in the scene appear hazier.

Adding a Volume Effect
The Volume atmospheric effect adds a fog and haze to the scene by coloring all scene objects with the designated color. When the volume effect is enabled, notice how the figure details are washed out by the fog effect. The volume effect also affects shadows.

[Figure 8-40] Smokey room atmospheric effect

Using Atmosphere Presets
The Volume effect is a fairly simplistic atmospheric effect that applies equal fading over the entire scene. Within the Wacros panel are several additional atmospheric presets that combine turbulence and noise to give the fog a more random, realistic look.

Clicking on the Create Atmosphere button in the Wacros panel opens a simple dialog box where you can choose Fog, Smoke, SmokyRoom, or Depth_Cue effects. Figure 8-40 shows a scene with three figures and the Smokey Room atmospheric effect.

Atmospheric effects are not visible in the Preview Window and can only be seen on scene objects when rendered.

Creating Controlled Atmospheres
Even though the Atmosphere node in the Material Room provides an easy way to add atmospheric effects, you are not limited to only using this method. Using a prop object with a cloud or noise material applied to it provides a similar effect and gives you much better control over where the fog is located and how it looks.

Adding a Hi-Res Square from the Primitives Prop folder in the Library and positioning it where the fog should be located provides a surface for the fog. Then add a Clouds, Noise, or Turbulence node to the Shader window and connect it to the Transparency and Transparency Edge channels and render the scene. If you connect the Clouds to the Alternative Diffuse channel, then you’ll be able to control the color of the fog also.