@Override
    public void postQueue(RenderQueue rq) {
        for (Filter filter : filters.getArray()) {
            if (filter.isEnabled()) {
                if (prof != null) prof.spStep(SpStep.ProcPostQueue, FPP, filter.getName());
                filter.postQueue(rq);
            }
        }
    }
renders a filter on a fullscreen quad
@param r
@param buff
@param mat
jme3-core/src/main/java/com/jme3/post/FilterPostProcessor.java