Gooch Shader

Resurrecting previous work by Bernard Kwok to implement Gooch shader

libraries/nprlib/nprlib_defs.mtlx

@@ -20,4 +20,11 @@
     <output name="out" type="vector3" default="0.0, 0.0, 1.0" />
   </nodedef>
 
+  <nodedef name="ND_gooch" node="gooch" version="1.0.0" isdefaultversion="true">
+    <input name="warm_color" type="color3" value="0.6, 0, 0"/>
+    <input name="cool_color" type="color3"  value="0, 0, 0.6"/>
+    <input name="normal" type="vector3" defaultgeomprop="Nworld" />
+    <input name="light_dir" type="vector3" value="0, 1, 1"/>
+    <output name="out" type="surfaceshader" />
+  </nodedef>
 </materialx>

libraries/nprlib/nprlib_ng.mtlx

@@ -0,0 +1,58 @@
+<?xml version="1.0"?>
+<materialx version="1.38">
+  <!--
+    Copyright Contributors to the MaterialX Project
+    SPDX-License-Identifier: Apache-2.0
+
+    Graph definitions of nprlib nodes included in the MaterialX specification.
+  -->
+
+<nodegraph name="IMPL_gooch" nodedef="ND_gooch">
+    <add name="add" type="vector3" >
+      <input name="in1" type="vector3" nodename="light"  />
+      <input name="in2" type="vector3" nodename="light"  />
+    </add>
+    <add name="add1" type="color3" >
+      <input name="in1" type="color3" nodename="mix"  />
+      <input name="in2" type="float" nodename="max1"  />
+    </add>
+    <dotproduct name="dotproduct" type="float" >
+      <input name="in1" type="vector3" interfacename="normal"  />
+      <input name="in2" type="vector3" nodename="normalize"  />
+    </dotproduct>
+    <dotproduct name="dotproduct1" type="float" >
+      <input name="in1" type="vector3" interfacename="normal"  />
+      <input name="in2" type="vector3" nodename="normalize1"  />
+    </dotproduct>
+    <constant name="light" type="vector3" >
+      <input name="value" type="vector3" interfacename="light_dir" />
+    </constant>
+    <max name="max1" type="float" >
+      <input name="in1" type="float" nodename="power"  />
+    </max>
+    <mix name="mix" type="color3" >
+      <input name="fg" type="color3" interfacename="cool_color" />
+      <input name="bg" type="color3" interfacename="warm_color" />
+      <input name="mix" type="float" nodename="dotproduct"  />
+    </mix>
+    <normalize name="normalize" type="vector3" >
+      <input name="in" type="vector3" nodename="light"  />
+    </normalize>
+    <normalize name="normalize1" type="vector3" >
+      <input name="in" type="vector3" nodename="add"  />
+    </normalize>
+    <power name="power" type="float" >
+      <input name="in1" type="float" nodename="dotproduct1"  />
+      <input name="in2" type="float" value="32"  />
+    </power>
+    <uniform_edf name="uniform_edf" type="EDF" >
+      <input name="color" type="color3" nodename="add1" />
+    </uniform_edf>
+    <surface name="gooch_shader" type="surfaceshader" >
+      <input name="bsdf" type="BSDF" value="" />
+      <input name="edf" type="EDF" nodename="uniform_edf" />
+      <input name="opacity" type="float" value="1" />
+    </surface>
+    <output name="out" type="surfaceshader" nodename="gooch_shader" />
+</nodegraph>
+</materialx>

resources/Materials/Examples/gooch_material.mtlx

@@ -0,0 +1,13 @@
+<?xml version="1.0"?>
+<materialx version="1.38">
+
+  <gooch name="SR_Gooch_Material" type="surfaceshader">
+    <input name="warm_color" type="color3" value="0.6, 0, 0"/>
+    <input name="cool_color" type="color3"  value="0, 0, 0.6"/>
+    <input name="light_dir" type="vector3" value="0, 1, 1"/>
+  </gooch>
+  <surfacematerial name="Gooch_Material" type="material">
+    <input name="surfaceshader" type="surfaceshader" nodename="SR_Gooch_Material" />
+  </surfacematerial>
+
+</materialx>