three.js/examples/materialx/open_pbr_surface_velvet.mtlx

<?xml version="1.0"?>
<materialx version="1.39" colorspace="lin_rec709">
  <surfacematerial name="Velvet" type="material">
    <input name="surfaceshader" type="surfaceshader" nodename="open_pbr_surface_surfaceshader" />
  </surfacematerial>
  <open_pbr_surface name="open_pbr_surface_surfaceshader" type="surfaceshader">
    <input name="base_color" type="color3" value="0.02, 0.02, 0.02" />
    <input name="specular_roughness" type="float" value="0.8" />
    <input name="fuzz_weight" type="float" value="1" />
    <input name="fuzz_color" type="color3" value="0.4, 0.4, 0.4" />
    <input name="fuzz_roughness" type="float" value="0.5" />
  </open_pbr_surface>
</materialx>