Add hextiled example material (#2356)

This changelist adds a visually-motivated example material for the `hextiledimage` node, providing a reference point for future language implementations and improvements.  For visibility, a note about missing implementations of `hextiledimage` and `hextilednormalmap` in MSL, OSL, and MDL has been added to the README.md for the MaterialX data libraries.

The two new image assets are from ambientCG (https://ambientcg.com/), which shares them under the Creative Commons CC0 1.0 Universal License (https://github.com/AcademySoftwareFoundation/MaterialX/blob/main/THIRD-PARTY.md#ambientcg-assets).

One image asset from very early MaterialX examples (marble.png) has been removed, as it no longer appears to be referenced in our repository.

Author: jstone-lucasfilm

libraries/README.md

@@ -75,3 +75,4 @@ This folder contains the standard data libraries for MaterialX, providing declar
     - point, directional, spot
 - Shader generation does not currently support:
     - `displacementshader` and `volumeshader` nodes for hardware shading targets (GLSL, MSL).
+    - `hextiledimage` and `hextilednormalmap` for MSL, OSL, and MDL.

resources/Images/marble.png

@@ -0,0 +1,42 @@
+<?xml version="1.0"?>
+<materialx version="1.39" colorspace="lin_rec709">
+  <nodegraph name="NG_OnyxHextiled" fileprefix="resources/Images/">
+    <input name="tiling" type="float" value="4.0" uiname="Tiling" uifolder="Hex Tiling" />
+    <input name="rotation" type="float" value="1.0" uiname="Rotation" uifolder="Hex Tiling" />
+    <input name="scale" type="float" value="1.0" uiname="Scale" uifolder="Hex Tiling" />
+    <input name="offset" type="float" value="1.0" uiname="Offset" uifolder="Hex Tiling" />
+    <input name="falloff" type="float" value="0.75" uiname="Falloff" uifolder="Hex Tiling" />
+    <convert name="tiling_vector2" type="vector2">
+      <input name="in" type="float" interfacename="tiling" />
+    </convert>
+    <hextiledimage name="image_color" type="color3">
+      <input name="file" type="filename" value="onyx_color.jpg" colorspace="srgb_texture" />
+      <input name="tiling" type="vector2" nodename="tiling_vector2" />
+      <input name="rotation" type="float" interfacename="rotation" />
+      <input name="scale" type="float" interfacename="scale" />
+      <input name="offset" type="float" interfacename="offset" />
+      <input name="falloff" type="float" interfacename="falloff" />
+    </hextiledimage>
+    <hextiledimage name="image_roughness" type="color3">
+      <input name="file" type="filename" value="onyx_roughness.jpg" colorspace="none" />
+      <input name="tiling" type="vector2" nodename="tiling_vector2" />
+      <input name="rotation" type="float" interfacename="rotation" />
+      <input name="scale" type="float" interfacename="scale" />
+      <input name="offset" type="float" interfacename="offset" />
+      <input name="falloff" type="float" interfacename="falloff" />
+    </hextiledimage>
+    <extract name="image_roughness_float" type="float">
+      <input name="in" type="color3" nodename="image_roughness" />
+      <input name="index" type="integer" value="0" />
+    </extract>
+    <output name="out_color" type="color3" nodename="image_color" />
+    <output name="out_roughness" type="float" nodename="image_roughness_float" />
+  </nodegraph>
+  <standard_surface name="N_StandardSurface" type="surfaceshader">
+    <input name="base_color" type="color3" nodegraph="NG_OnyxHextiled" output="out_color" />
+    <input name="specular_roughness" type="float" nodegraph="NG_OnyxHextiled" output="out_roughness" />
+  </standard_surface>
+  <surfacematerial name="M_OnyxHextiled" type="material">
+    <input name="surfaceshader" type="surfaceshader" nodename="N_StandardSurface" />
+  </surfacematerial>
+</materialx>

resources/Images/onyx_color.jpg

@@ -50,6 +50,7 @@ class MdlShaderGeneratorTester : public GenShaderUtil::ShaderGeneratorTester
             _skipFiles.insert("heighttonormal_in_nodegraph.mtlx");
         }
 
+        _skipFiles.insert("standard_surface_onyx_hextiled.mtlx");
         _skipFiles.insert("hextiled.mtlx");
 
         ShaderGeneratorTester::addSkipFiles();

resources/Images/onyx_roughness.jpg

@@ -43,6 +43,7 @@ class MslShaderGeneratorTester : public GenShaderUtil::ShaderGeneratorTester
 
     void addSkipFiles() override
     {
+        _skipFiles.insert("standard_surface_onyx_hextiled.mtlx");
         _skipFiles.insert("hextiled.mtlx");
     }
 

resources/Materials/TestSuite/pbrlib/surfaceshader/standard_surface_onyx_hextiled.mtlx

@@ -45,6 +45,7 @@ class OslShaderGeneratorTester : public GenShaderUtil::ShaderGeneratorTester
 
     void addSkipFiles() override
     {
+        _skipFiles.insert("standard_surface_onyx_hextiled.mtlx");
         _skipFiles.insert("hextiled.mtlx");
     }