message: Changed default value and unit on thin_film_brdf.thickness.
diff: -->
  <nodedef name="ND_thin_film_brdf" node="thin_film_brdf" bsdf="R" nodegroup="pbr"
  doc="Adds an iridescent thin film layer over a microfacet base BSDF.">
  - <input name="thickness" type="float" value="0.001"/>
  + <input name="thickness" type="float" value="1000" unittype="distance" unit="nanometer"/>
  <input name="ior" type="float" value="1.5"/>
  <input name="base" type="BSDF" value=""/>
  <output name="out" type="BSDF"/>
  