title: SVG filters and interpolated values
body: <p>I am creating a visualization with d3.js, and the effect I would like to achieve relies on a filter using feFlood and feBlend. For each path in the visualization, I need to interpolate a different <code>flood-opacity</code> value for the <code>feFlood</code> filter primitive. The filter is pretty simple:</p>
  
  <pre><code>&lt;filter id="multiplyOverlay" x="0" y="0" width="100%" height="100%"&gt;
      &lt;feFlood flood-color="steelblue" flood-opacity=".1" /&gt;
      &lt;feBlend mode="multiply" in2="SourceGraphic"/&gt;
  &lt;/filter&gt;
  </code></pre>
  
  <p>I don't believe there is any way to pass a value in to the filter. Will I need to create a new filter for each path (about 200) in the visualization with the appropriate <code>flood-opacity</code> value? Or is there some other way to achieve this?</p>