public void setFogDensity(float fogDensity) {
        if (material != null) {
            material.setFloat("FogDensity", fogDensity);
        }
        this.fogDensity = fogDensity;
    }
Sets the density of the fog, a high value gives a thick fog

@param fogDensity the desired density (default=0.7)
jme3-effects/src/main/java/com/jme3/post/filters/FogFilter.java