Simplified implementation of "decoupled IOR" for MaterialX

Author: portsmouth

reference/open_pbr_surface.mtlx

@@ -378,7 +378,7 @@
     </ifgreater>
     <dielectric_bsdf name="dielectric_transmission" type="BSDF">
       <input name="tint" type="color3" nodename="if_transmission_tint" />
-      <input name="ior" type="float" nodename="modulated_eta_s" />
+      <input name="ior" type="float" nodename="eta_s" />
       <input name="roughness" type="vector2" nodename="main_roughness" />
       <input name="normal" type="vector3" interfacename="geometry_normal" />
       <input name="tangent" type="vector3" interfacename="geometry_tangent" />