docs: private void processElementClipping(GeneratorSingleCluster cluster, Node cur) {
      double[] cmin = null, cmax = null;
  
      String minstr = ((Element) cur).getAttribute(ATTR_MIN);
      if(minstr != null && minstr.length() > 0) {
        cmin = parseVector(minstr);
      }
      String maxstr = ((Element) cur).getAttribute(ATTR_MAX);
      if(maxstr != null && maxstr.length() > 0) {
        cmax = parseVector(maxstr);
      }
      if(cmin == null || cmax == null) {
        throw new AbortException("No or incomplete clipping vectors given.");
      }
  
      // *** set clipping
      cluster.setClipping(cmin, cmax);
  
      // TODO: check for unknown attributes.
      XMLNodeIterator iter = new XMLNodeIterator(cur.getFirstChild());
      while(iter.hasNext()) {
        Node child = iter.next();
        if(child.getNodeType() == Node.ELEMENT_NODE) {
          LOG.warning("Unknown element in XML specification file: " + child.getNodeName());
        }
      }
    }