@Override
    public void postFrame(FrameBuffer out) {
        if (!noOccluders) {
            postshadowMat.setMatrix4("LightViewProjectionMatrix", shadowCam.getViewProjectionMatrix());
            renderManager.setForcedMaterial(postshadowMat);
            viewPort.getQueue().renderShadowQueue(lightReceivers, renderManager, viewPort.getCamera(), true);
            renderManager.setForcedMaterial(null);
        }
    }
debug only
@return the pre-existing instance
jme3-core/src/main/java/com/jme3/shadow/BasicShadowRenderer.java