public RenderQueue.Bucket getQueueBucket() {
        if (queueBucket != RenderQueue.Bucket.Inherit) {
            return queueBucket;
        } else if (parent != null) {
            return parent.getQueueBucket();
        } else {
            return RenderQueue.Bucket.Opaque;
        }
    }
Returns this spatial's render-queue bucket. If the mode is set to inherit,
then the spatial gets its render-queue bucket from its parent.

@return The spatial's current render-queue bucket.
jme3-core/src/main/java/com/jme3/scene/Spatial.java