Update specification and reference to v0.4 (#178)

Author: jstone-lucasfilm

index.html

@@ -7,7 +7,7 @@
 <center>Zap Andersson, Paul Edmondson, Julien Guertault, Adrien Herubel, Alan King, </center>
 <center>Peter Kutz, Andréa Machizaud, Jamie Portsmouth, Frédéric Servant.</center>
 
-<center>*Version 0.3, 2024-02-21. A joint work of Adobe and Autodesk*</center>
+<center>*Version 0.4, 2024-04-30. A joint work of Adobe and Autodesk*</center>
 
 This document is a specification of a surface shading model: the OpenPBR Surface model. Designed as an über-surface, it aims to be capable of accurately modeling the vast majority of CG materials used in practical visual effects and feature animation productions. The model has been developed as a synthesis of the Autodesk Standard Surface and the Adobe Standard Material models.
 

reference/open_pbr_surface.mtlx

@@ -3,7 +3,7 @@
   <!--
     OpenPBR Surface node definition
   -->
-  <nodedef name="ND_open_pbr_surface_surfaceshader" node="open_pbr_surface" nodegroup="pbr" version="0.3" isdefaultversion="true"
+  <nodedef name="ND_open_pbr_surface_surfaceshader" node="open_pbr_surface" nodegroup="pbr" version="0.4" isdefaultversion="true"
            doc="OpenPBR Surface Shading Model">
     <input name="base_weight" type="float" value="1.0" uimin="0.0" uimax="1.0" uiname="Base Weight" uifolder="Base"
            doc="Multiplier on the intensity of the reflection from the diffuse and metallic base." />