public float getShadowZFadeLength() {
        if (fadeInfo != null) {
            return zFarOverride - fadeInfo.x;
        }
        return 0f;
    }
get the length over which the shadow will fade out when using a
shadowZextend

@return the fade length in world units
jme3-core/src/main/java/com/jme3/shadow/PssmShadowRenderer.java