             onclick="toggleHelp('mapmask')">mapmask</a>
        </code>
        <div id="mapmask_help" style="display: none;
             padding-left: 16px; margin-top: 4px; border-top: 1px dashed
             #cccccc;">
	     <pre>
array (up to 30 elements) of masking algorithms for mapping input data
associated with the array of streams.  valid options are map only from
valid src points, map only to valid destination points, ignore all
masks, map only from valid src points to valid destination points.
v