public void addFilter(Filter filter) {
        if (filter == null) {
            throw new IllegalArgumentException("Filter cannot be null.");
        }
        filters.add(filter);

        if (isInitialized()) {
            initFilter(filter, viewPort);
        }

        setFilterState(filter, filter.isEnabled());

    }
Adds a filter to the filters list<br>
@param filter the filter to add
jme3-core/src/main/java/com/jme3/post/FilterPostProcessor.java