public void setFogDistance(float fogDistance) {
        if (material != null) {
            material.setFloat("FogDistance", fogDistance);
        }
        this.fogDistance = fogDistance;
    }
the distance of the fog. the higher the value the distant the fog looks

@param fogDistance the desired distance (in world units, default=1000)
jme3-effects/src/main/java/com/jme3/post/filters/FogFilter.java