From 94eb3ac4d96d44c88f0ad5c2ef1075f6021b2bf9 Mon Sep 17 00:00:00 2001
From: Bernard Kwok <kwokcb@gmail.com>
Date: Sat, 27 Jan 2024 12:08:24 -0500
Subject: [PATCH] Change to fit logic from Gooch paper.

---
 libraries/nprlib/nprlib_defs.mtlx             | 13 ++--
 libraries/nprlib/nprlib_ng.mtlx               | 78 ++++++++++++++++---
 .../Examples/npr/gooch_material.mtlx          | 24 +++---
 .../Materials/TestSuite/nprlib/gooch.mtlx     | 28 +++----
 4 files changed, 95 insertions(+), 48 deletions(-)

diff --git a/libraries/nprlib/nprlib_defs.mtlx b/libraries/nprlib/nprlib_defs.mtlx
index aa44e4062a..f9e2e6ebbf 100644
--- a/libraries/nprlib/nprlib_defs.mtlx
+++ b/libraries/nprlib/nprlib_defs.mtlx
@@ -44,11 +44,14 @@
     Compute Gooch Shading.
   -->
   <nodedef name="ND_gooch_shade" node="gooch_shade" nodegroup="npr" doc="Compute Gooch shading">
-    <input name="warm_color" type="color3" value="0.6, 0, 0" uiname="Warm Color" doc="Warm diffuse color"/>
-    <input name="cool_color" type="color3" value="0, 0, 0.6" uiname="Cool Color" doc="Cool diffuse color"/>
-    <input name="shininess" type="float" value="8" uimin="1" uimax="64" doc="Specular shininess"/>
-    <input name="specular_color" type="color3" value="0.6, 0.6, 0.6" uiname="Specular Color" doc="Specular color"/>
-    <input name="light_direction" type="vector3" value="1, -0.5, -0.5" uiname="Light Direction" doc="Light vector in world space"/>
+    <input name="diffuse_color" type="color3" value="0.8, 0.8, 0.8" doc="Diffuse Color" uiname="Diffuse Color" />
+    <input name="blue_tone" type="float" value="0.55" uimin="0" uimax="1" doc="Blue tone" uiname="Blue Tone" />
+    <input name="yellow_tone" type="float" value="0.3" uimin="0" uimax="1" doc="Yellow Tone" uiname="Yellow Tone" />
+    <input name="diffuse_strength" type="float" value="0.25" uimin="0" uimax="1" doc="Diffuse Strength" uiname="Diffuse Strength" />
+    <input name="luminance_shift" type="float" value="0.5" uimin="0" uimax="1" doc="Luminance Shift" uiname="Luminance Shift" />
+    <input name="shininess" type="float" value="32" uimin="1" uimax="64" uiname="Shininess" doc="Specular shininess" />
+    <input name="specular_color" type="color3" value="1, 1, 1" uiname="Specular Color" doc="Specular color" />
+    <input name="light_direction" type="vector3" value="1, -0.5, -0.5" uiname="Light Direction" doc="Light vector" />
     <output name="out" type="color3" />
   </nodedef>
 
diff --git a/libraries/nprlib/nprlib_ng.mtlx b/libraries/nprlib/nprlib_ng.mtlx
index 79a406be03..c7b5350fcd 100644
--- a/libraries/nprlib/nprlib_ng.mtlx
+++ b/libraries/nprlib/nprlib_ng.mtlx
@@ -53,17 +53,12 @@
       <input name="space" type="string" value="world" />
     </normal>
     <normalize name="normalized_light_dir" type="vector3">
-      <input name="in" type="vector3" nodename="invert_light_dir" />
+      <input name="in" type="vector3" interfacename="light_direction" />
     </normalize>
     <dotproduct name="NdotL" type="float">
       <input name="in1" type="vector3" nodename="N" />
       <input name="in2" type="vector3" nodename="normalized_light_dir" />
     </dotproduct>
-    <mix name="diffuse" type="color3">
-      <input name="fg" type="color3" interfacename="warm_color" />
-      <input name="bg" type="color3" interfacename="cool_color" />
-      <input name="mix" type="float" nodename="max_float" />
-    </mix>
     <power name="specular" type="float">
       <input name="in1" type="float" nodename="max1" />
       <input name="in2" type="float" interfacename="shininess" />
@@ -72,9 +67,6 @@
       <input name="in1" type="float" nodename="VdotR" />
       <input name="in2" type="float" value="0" />
     </max>
-    <max name="max_float" type="float">
-      <input name="in1" type="float" nodename="NdotL" />
-    </max>
     <viewdirection name="view" type="vector3" />
     <dotproduct name="NdotI" type="float">
       <input name="in1" type="vector3" nodename="normalize_vector4" />
@@ -85,7 +77,7 @@
       <input name="in2" type="float" value="2" />
     </multiply>
     <dotproduct name="VdotR" type="float">
-      <input name="in1" type="vector3" nodename="normalized_light_dir" />
+      <input name="in1" type="vector3" nodename="invert_light_dir" />
       <input name="in2" type="vector3" nodename="I_NdotI_N_2" />
     </dotproduct>
     <multiply name="multiply_vector3FA" type="vector3">
@@ -115,9 +107,73 @@
       <input name="in2" type="color3" nodename="multiply_color3FA" />
     </add>
     <multiply name="invert_light_dir" type="vector3">
-      <input name="in1" type="vector3" interfacename="light_direction" />
+      <input name="in1" type="vector3" nodename="normalized_light_dir" />
       <input name="in2" type="vector3" value="-1, -1, -1" />
     </multiply>
+    <swizzle name="swizzle_float_color3" type="color3">
+      <input name="in" type="float" interfacename="blue_tone" />
+      <input name="channels" type="string" value="00b" />
+    </swizzle>
+    <swizzle name="swizzle_float_color4" type="color3">
+      <input name="in" type="float" interfacename="yellow_tone" />
+      <input name="channels" type="string" value="rg0" />
+    </swizzle>
+    <add name="one_plus_NdotL" type="float">
+      <input name="in2" type="float" nodename="NdotL" />
+      <input name="in1" type="float" value="1" />
+    </add>
+    <divide name="one_plus_NdotL_div_2" type="float">
+      <input name="in1" type="float" nodename="one_plus_NdotL" />
+      <input name="in2" type="float" value="2" />
+    </divide>
+    <subtract name="one_minus_NdotL" type="float">
+      <input name="in2" type="float" nodename="NdotL" />
+      <input name="in1" type="float" value="1" />
+    </subtract>
+    <divide name="one_minus_NdotL_div_2" type="float">
+      <input name="in1" type="float" nodename="one_minus_NdotL" />
+      <input name="in2" type="float" value="2" />
+    </divide>
+    <convert name="convert_float_color3" type="color3">
+      <input name="in" type="float" interfacename="diffuse_strength" />
+    </convert>
+    <multiply name="multiply_color3" type="color3">
+      <input name="in1" type="color3" interfacename="diffuse_color" />
+      <input name="in2" type="color3" nodename="convert_float_color3" />
+    </multiply>
+    <add name="k_cool" type="color3">
+      <input name="in1" type="color3" nodename="multiply_color3" />
+      <input name="in2" type="color3" nodename="swizzle_float_color3" />
+    </add>
+    <add name="k_warm" type="color3">
+      <input name="in2" type="color3" nodename="swizzle_float_color4" />
+      <input name="in1" type="color3" nodename="multiply_color4" />
+    </add>
+    <convert name="convert_float_color4" type="color3">
+      <input name="in" type="float" interfacename="luminance_shift" />
+    </convert>
+    <multiply name="multiply_color4" type="color3">
+      <input name="in1" type="color3" interfacename="diffuse_color" />
+      <input name="in2" type="color3" nodename="convert_float_color4" />
+    </multiply>
+    <convert name="convert_float_color5" type="color3">
+      <input name="in" type="float" nodename="one_plus_NdotL_div_2" />
+    </convert>
+    <multiply name="cool" type="color3">
+      <input name="in2" type="color3" nodename="convert_float_color5" />
+      <input name="in1" type="color3" nodename="k_cool" />
+    </multiply>
+    <convert name="convert_float_color6" type="color3">
+      <input name="in" type="float" nodename="one_minus_NdotL_div_2" />
+    </convert>
+    <multiply name="warm" type="color3">
+      <input name="in1" type="color3" nodename="k_warm" />
+      <input name="in2" type="color3" nodename="convert_float_color6" />
+    </multiply>
+    <add name="diffuse" type="color3">
+      <input name="in1" type="color3" nodename="cool" />
+      <input name="in2" type="color3" nodename="warm" />
+    </add>
     <output name="out" type="color3" nodename="final_color" />
   </nodegraph>
   
diff --git a/resources/Materials/Examples/npr/gooch_material.mtlx b/resources/Materials/Examples/npr/gooch_material.mtlx
index 5f1dec7535..708dec0072 100644
--- a/resources/Materials/Examples/npr/gooch_material.mtlx
+++ b/resources/Materials/Examples/npr/gooch_material.mtlx
@@ -9,19 +9,16 @@
       <input name="file" type="filename" value="brass_roughness.jpg" />
       <input name="uvtiling" type="vector2" value="1.0, 1.0" />
     </tiledimage>
-
     <gooch_shade name="gooch1" type="color3">
-     <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_direction" type="vector3" value="0, 1, 1"/>
-     <input name="specular_color" type="color3" value="0.8, 0.8, 0.8"/>
-   </gooch_shade>
-
+      <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_direction" type="vector3" value="0, 1, 1" />
+      <input name="specular_color" type="color3" value="0.8, 0.8, 0.8" />
+    </gooch_shade>
     <output name="out_basecolor" type="color3" nodename="gooch1" />
     <output name="out_color" type="color3" nodename="image_color" />
     <output name="out_roughness" type="float" nodename="image_roughness" />
   </nodegraph>
-  
   <standard_surface name="SR_brass1" type="surfaceshader">
     <input name="base" type="float" value="1" />
     <input name="base_color" type="color3" nodegraph="NG_brass1" output="out_basecolor" />
@@ -35,12 +32,13 @@
   <surfacematerial name="Tiled_Brass" type="material">
     <input name="surfaceshader" type="surfaceshader" nodename="SR_brass1" />
   </surfacematerial>
-
   <gooch_shade name="gooch_color" type="color3">
-    <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_direction" type="vector3" value="0, 1, 1"/>
-    <input name="specular_color" type="color3" value="0.8, 0.8, 0.8"/>
+    <input name="diffuse_color" type="color3" value="1, 0, 0" />
+    <input name="yellow_tone" type="float" value="0" />
+    <input name="blue_tone" type="float" value="1" />
+    <input name="diffuse_strength" type="float" value="0" />
+    <input name="luminance_shift" type="float" value="0.522" />
+    <input name="shininess" type="float" value="16" />
   </gooch_shade>
   <surface_unlit name="unlit_surface" type="surfaceshader">
     <input name="emission_color" type="color3" nodename="gooch_color" />
diff --git a/resources/Materials/TestSuite/nprlib/gooch.mtlx b/resources/Materials/TestSuite/nprlib/gooch.mtlx
index 30edb43367..00ad79df6b 100644
--- a/resources/Materials/TestSuite/nprlib/gooch.mtlx
+++ b/resources/Materials/TestSuite/nprlib/gooch.mtlx
@@ -1,23 +1,13 @@
+<?xml version="1.0"?>
 <materialx version="1.38">
-  <!--
-    Copyright Contributors to the MaterialX Project
-    SPDX-License-Identifier: Apache-2.0
-
-    Graph definitions of standard nodes included in the MaterialX specification.
-  -->
-
-  <!-- ======================================================================== -->
-  <!-- Gooch Shading Example                                                    -->
-  <!-- ======================================================================== -->
-
-  <!--
-    Node: <gooch_shade>
-  -->
   <gooch_shade name="gooch1" type="color3">
-    <input name="warm_color" type="color3" value="0.701712, 0.37992, 0.111519" />
-    <input name="cool_color" type="color3" value="0.073756, 0, 0.486553" />
-    <input name="shininess" type="float" value="10" />
-    <input name="specular_color" type="color3" value="0.929095, 0.603842, 0.0817786" />
+    <input name="diffuse_strength" type="float" value="0.269" />
+    <input name="diffuse_color" type="color3" value="0, 0.535452, 0.068077" />
+    <input name="luminance_shift" type="float" value="0.374" />
+    <input name="yellow_tone" type="float" value="0.325" />
+    <input name="blue_tone" type="float" value="0.491" />
+    <input name="light_direction" type="vector3" value="-1, -0.5, -0.5" />
+    <input name="shininess" type="float" value="5" />
   </gooch_shade>
   <surface_unlit name="unlit_surface" type="surfaceshader">
     <input name="emission_color" type="color3" nodename="gooch1" />
@@ -27,4 +17,4 @@
     <input name="surfaceshader" type="surfaceshader" nodename="unlit_surface" />
     <input name="displacementshader" type="displacementshader" value="" />
   </surfacematerial>
-</materialx>
\ No newline at end of file
+</materialx>