From 2f169d152f295114efe982ab06a74bfd930bb540 Mon Sep 17 00:00:00 2001
From: ld-kerley <154285602+ld-kerley@users.noreply.github.com>
Date: Fri, 26 Jan 2024 15:19:06 -0800
Subject: [PATCH 1/2] Add invert node to specification (#1676)

The node exists in the standard library code, but is missing from the specification.
---
 documents/Specification/MaterialX.Specification.md | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/documents/Specification/MaterialX.Specification.md b/documents/Specification/MaterialX.Specification.md
index 895b4756c5..42b6cbbcaf 100644
--- a/documents/Specification/MaterialX.Specification.md
+++ b/documents/Specification/MaterialX.Specification.md
@@ -1084,6 +1084,12 @@ Math nodes have one or two spatially-varying inputs, and are used to perform a m
     * `in1` (float or color<em>N</em> or vector<em>N</em>): the value or nodename for the primary input
     * `in2` (same type as `in1` or float): the modulo value or nodename to divide by, cannot be 0 in any channel; default is 1.0 in all channels, which effectively returns the fractional part of a float value
 
+<a id="node-invert"> </a>
+
+* **`invert`**: subtract the incoming float/color/vector from "amount" in all channels, outputting: `amount - in`.
+    * `in` (float or color<em>N</em> or vector<em>N</em>): the value or nodename for the primary input
+    * `amount` (same type as `in` or float): the value or nodename to subtract from; default is 1.0 in all channels
+
 <a id="node-absval"> </a>
 
 * **`absval`**: the per-channel absolute value of the incoming float/color/vector.

From d1e08f3e9141fd1d40b018c5230175967c930dcc Mon Sep 17 00:00:00 2001
From: Jonathan Stone <jstone@lucasfilm.com>
Date: Sat, 27 Jan 2024 16:42:31 -0800
Subject: [PATCH 2/2] Improvements to facingratio

- Fix syntax of input default values.
- Use the invert node in facingratio for compactness.
- Clarify the edge brighten example material.
---
 libraries/nprlib/nprlib_defs.mtlx                 |  4 ++--
 libraries/nprlib/nprlib_ng.mtlx                   |  7 +++----
 .../Materials/TestSuite/nprlib/edge_brighten.mtlx | 15 +++++++--------
 3 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/libraries/nprlib/nprlib_defs.mtlx b/libraries/nprlib/nprlib_defs.mtlx
index a8d282d0c4..dfbaa5b5f6 100644
--- a/libraries/nprlib/nprlib_defs.mtlx
+++ b/libraries/nprlib/nprlib_defs.mtlx
@@ -34,8 +34,8 @@
   <nodedef name="ND_facingratio_float" node="facingratio" nodegroup="npr">
     <input name="viewdirection" type="vector3" defaultgeomprop="Vworld" />
     <input name="normal" type="vector3" defaultgeomprop="Nworld" />
-    <input name="faceforward" type="boolean" default="true" />
-    <input name="invert" type="boolean" default="false" />
+    <input name="faceforward" type="boolean" value="true" />
+    <input name="invert" type="boolean" value="false" />
     <output name="out" type="float" default="0.0" />
   </nodedef>
 
diff --git a/libraries/nprlib/nprlib_ng.mtlx b/libraries/nprlib/nprlib_ng.mtlx
index c287c2ef79..0bd7e334e5 100644
--- a/libraries/nprlib/nprlib_ng.mtlx
+++ b/libraries/nprlib/nprlib_ng.mtlx
@@ -32,10 +32,9 @@
       <input name="in1" type="float" nodename="N_absval" />
       <input name="in2" type="float" nodename="N_scale" />
     </ifequal>
-    <subtract name="N_invert" type="float">
-      <input name="in1" type="float" value="1" />
-      <input name="in2" type="float" nodename="N_facing" />
-    </subtract>
+    <invert name="N_invert" type="float">
+      <input name="in" type="float" nodename="N_facing" />
+    </invert>
     <ifequal name="N_result" type="float">
       <input name="value1" type="boolean" interfacename="invert" />
       <input name="value2" type="boolean" value="true" />
diff --git a/resources/Materials/TestSuite/nprlib/edge_brighten.mtlx b/resources/Materials/TestSuite/nprlib/edge_brighten.mtlx
index dc06b76d98..8ce3affd40 100644
--- a/resources/Materials/TestSuite/nprlib/edge_brighten.mtlx
+++ b/resources/Materials/TestSuite/nprlib/edge_brighten.mtlx
@@ -1,17 +1,16 @@
 <?xml version="1.0"?>
 <materialx version="1.38" colorspace="lin_rec709">
   <nodegraph name="edge_brighten">
-    <facingratio name="facingratio_float" type="float" />
-    <clamp name="clamp_float" type="float">
-      <input name="in" type="float" nodename="facingratio_float" />
-    </clamp>
+    <facingratio name="facingratio_float" type="float">
+      <input name="invert" type="boolean" value="true" />
+    </facingratio>
     <power name="power_float" type="float">
-      <input name="in1" type="float" nodename="clamp_float" />
-      <input name="in2" type="float" value="0.2" />
+      <input name="in1" type="float" nodename="facingratio_float" />
+      <input name="in2" type="float" value="3.0" />
     </power>
     <mix name="mix_color3" type="color3">
-      <input name="fg" type="color3" value="0, 0.0986187, 0.186275" />
-      <input name="bg" type="color3" value="0.735294, 0.735294, 0.735294" />
+      <input name="bg" type="color3" value="0, 0.0986187, 0.186275" />
+      <input name="fg" type="color3" value="0.735294, 0.735294, 0.735294" />
       <input name="mix" type="float" nodename="power_float" />
     </mix>
     <output name="out" type="color3" nodename="mix_color3" />