Convert text into an HTML canvas and use it as a Shapespark texture.

body-end.html

<style>
#input-section {
   position: absolute;
   top: 0px;
   width: 256px;
   z-index: 200;
}
</style>

<div id="input-section">
  <input id="text-input" type="text">
</div>

<script>
  var viewer = WALK.getViewer();
  viewer.setMaterialEditable('rug');

  function textToCanvas(text) {
    var canvas = document.createElement('canvas');
    canvas.width = 1024;
    canvas.height = 1024;
    var ctx = canvas.getContext('2d');
    ctx.fillStyle = '#add8e6';
    ctx.fillRect(0, 0, canvas.width, canvas.height);

    ctx.font = '700 128px Noto Sans'
    ctx.fillStyle = '#ffffff';
    ctx.textAlign = 'center';
    ctx.textBaseline = 'middle';
    ctx.fillText(text, canvas.width / 2, canvas.height / 2);
    return canvas;
  }

  function sceneReadyToDisplay() {
    var rugMaterial = viewer.findMaterial('rug');
    var textInput = document.getElementById('text-input');
    textInput.addEventListener('input', function(event) {
      var canvas = textToCanvas(event.target.value);
      var texture = new WALK.Texture(canvas);
      texture.width = canvas.width;
      texture.height = canvas.height;
      texture.hasAlpha = false;
      texture.minFilter = GLC.LINEAR;
      texture.wrapS = GLC.REPEAT;
      texture.wrapT = GLC.REPEAT;
      texture.needsUpdate = true;
      texture.notifyLoaded();

      if (rugMaterial.baseColorTexture) {
        rugMaterial.baseColorTexture.dispose();
      }
      rugMaterial.baseColorTexture = texture;
      viewer.requestFrame();
    });
  };
  viewer.onSceneReadyToDisplay(sceneReadyToDisplay);
</script>