To add a fog effect to a scene, a FogNode must be added. The FogNode references a Fog instance which defines the fog settings. Fog affects the whole scene.

The fog can be configured to create a distance-based fog:

The fog can also depend on the height:

The y-position of the FogNode defines the "base level" of the fog layer. The y-position of the node can be changed to move the height-based fog up/down.

You can add more than one FogNode to a scene to combine fog effects.

In forward rendering, the fog is applied when the models are rendered. That means, the models use a single effect which computes the shading and applies the fog color. For example, the XNA stock effects support distance-based fog (but they do not support height-based fog or more than one fog effect per scene).

In deferred rendering, the fog can be applied in a separate rendering step using the FogRenderer. The advantage is that the effects used to render the meshes do not need to handle fog, but this does not work for alpha-blended meshes.

The FogRenderer is a SceneNodeRenderer which handles FogNodes. The FogRenderer works only if a valid depth buffer is set in the render context (property GBuffer0).

The FogRenderer is usually rendered after all opaque objects:

// Render opaque objects...

// Render fog.
fogRenderer.Render(fogNodes, context);

// Render alpha-blended objects...