指向Y

html,
body,
svg {
  height: 100%;
}

<svg viewBox="0 0 420 200" xmlns="http://www.w3.org/2000/svg">
  <filter id="lighting1" x="0" y="0" width="100%" height="100%">
    <feDiffuseLighting in="SourceGraphic">
      <feSpotLight x="60" y="60" z="50" pointsAtY="0" />
    </feDiffuseLighting>
  </filter>
  <filter id="lighting2" x="0" y="0" width="100%" height="100%">
    <feDiffuseLighting in="SourceGraphic">
      <feSpotLight x="60" y="60" z="50" pointsAtY="400" />
    </feDiffuseLighting>
  </filter>

  <rect x="0" y="0" width="200" height="200" filter="url(#lighting1)" />
  <rect x="220" y="0" width="200" height="200" filter="url(#lighting2)" />
</svg>