Allow runtime adjustment of MaterialX Search Paths.

UsdMtlx uses the two environment variables PXR_USDMTLX_STDLIB_SEARCH_PATHS and
PXR_USDMTLX_PUGIN_SEARCH_PATHS for the user to specify where to find the necessary
MaterialX files. The imaging side does not do this. This change adds that behavior to HdMtlx.
So now, if the location of the MaterialX provided libraries folder changes from the location
originally found at runtime (stored in PXR_MATERIALX_STDLIB_DIR) the new location(s)
can be indicated with PXR_MTLX_STDLIB_SEARCH_PATHS. The location(s) to any custom
MaterialX files can be indicated with PXR_MTLX_PLUGIN_SEARCH_PATHS.

(Based on GitHub PR PixarAnimationStudios#1628 by @vlasovi)

Fixes PixarAnimationStudios#1586

(Internal change: 2197997)

pxr/imaging/hdMtlx/CMakeLists.txt

@@ -1,6 +1,8 @@
 set(PXR_PREFIX pxr/imaging)
 set(PXR_PACKAGE hdMtlx)
 
+add_definitions(-DPXR_MATERIALX_STDLIB_DIR="${MATERIALX_STDLIB_DIR}")
+
 pxr_library(hdMtlx
     LIBRARIES
         gf

pxr/imaging/hdMtlx/hdMtlx.cpp

@@ -30,7 +30,10 @@
 
 #include "pxr/usd/sdf/path.h"
 #include "pxr/usd/sdr/registry.h"
+
+#include "pxr/base/arch/fileSystem.h"
 #include "pxr/base/tf/diagnostic.h"
+#include "pxr/base/tf/getenv.h"
 
 #include <MaterialXCore/Document.h>
 #include <MaterialXCore/Node.h>
@@ -41,6 +44,55 @@ namespace mx = MaterialX;
 
 PXR_NAMESPACE_OPEN_SCOPE
 
+static const NdrStringVec
+_GetSearchPathsFromEnvVar(const char* name)
+{
+    const std::string paths = TfGetenv(name);
+    return !paths.empty() 
+                ? TfStringSplit(paths, ARCH_PATH_LIST_SEP) 
+                : NdrStringVec();
+}
+
+static mx::FileSearchPath
+_ComputeSearchPaths()
+{
+    mx::FileSearchPath searchPaths;
+    // Add any additional custom mtlx path(s)
+    // Note this is the same envar used in UsdMtlxDiscoveryPlugin. This is used
+    // to indicate the location of any additional custom mtlx files.
+    static const auto customSearchPaths =
+        _GetSearchPathsFromEnvVar("PXR_MTLX_PLUGIN_SEARCH_PATHS");
+    for (auto path : customSearchPaths) {
+        searchPaths.append(mx::FilePath(path));
+    }
+
+    // Add the MaterialX/libraries path(s)
+    // Note this is the same envar used in UsdMtlxStandardLibraryPaths() 
+    // This is used to indicate the location of the MaterialX/libraries folder 
+    // if moved/changed from the path initilialized in PXR_MATERIALX_STDLIB_DIR.
+    static const auto stdlibSearchPaths =
+        _GetSearchPathsFromEnvVar("PXR_MTLX_STDLIB_SEARCH_PATHS");
+    for (auto path : stdlibSearchPaths) {
+        searchPaths.append(mx::FilePath(path));
+    }
+
+    // Add path to the MaterialX standard library discovered at build time.
+    searchPaths.append(mx::FilePath(PXR_MATERIALX_STDLIB_DIR));
+
+    return searchPaths;
+}
+
+// Return the MaterialX search paths. In order, this includes:
+// - Paths set in the environment variable 'PXR_MTLX_PLUGIN_SEARCH_PATHS'
+// - Paths set in the environment variable 'PXR_MTLX_STDLIB_SEARCH_PATHS'
+// - Path to the MaterialX standard library discovered at build time.
+const mx::FileSearchPath &
+HdMtlxSearchPaths()
+{
+    static const mx::FileSearchPath searchPaths = _ComputeSearchPaths();
+    return searchPaths;
+}
+
 // Return the MaterialX Node Type based on the corresponding NodeDef name, 
 // which is stored as the hdNodeType. 
 static TfToken

pxr/imaging/hdMtlx/hdMtlx.h

@@ -31,6 +31,7 @@
 #include <unordered_map>
 
 namespace MaterialX {
+    class FileSearchPath;
     using DocumentPtr = std::shared_ptr<class Document>;
     using StringMap = std::unordered_map<std::string, std::string>;
 }
@@ -42,6 +43,14 @@ class VtValue;
 struct HdMaterialNetwork2;
 struct HdMaterialNode2;
 
+/// Return the MaterialX search paths. In order, this includes:
+/// - Paths set in the environment variable 'PXR_MTLX_PLUGIN_SEARCH_PATHS'
+/// - Paths set in the environment variable 'PXR_MTLX_STDLIB_SEARCH_PATHS'
+/// - Path to the MaterialX standard library discovered at build time.
+HDMTLX_API
+const MaterialX::FileSearchPath&
+HdMtlxSearchPaths();
+
 /// Converts the HdParameterValue to a string MaterialX can understand
 HDMTLX_API
 std::string

pxr/imaging/hdSt/CMakeLists.txt

@@ -21,9 +21,6 @@ set(optionalIncludeDirs "")
 set(optionalPublicClasses "")
 set(optionalPrivateClasses "")
 if (${PXR_ENABLE_MATERIALX_SUPPORT})
-    add_definitions(-DPXR_MATERIALX_STDLIB_DIR="${MATERIALX_STDLIB_DIR}")
-    add_definitions(-DPXR_MATERIALX_BASE_DIR="${MATERIALX_BASE_DIR}")
-
     list(APPEND optionalLibs ${MATERIALX_LIBRARIES} hdMtlx)
     list(APPEND optionalIncludeDirs ${MATERIALX_INCLUDE_DIRS})
     list(APPEND optionalPrivateClasses

pxr/imaging/hdSt/materialXFilter.cpp

@@ -503,8 +503,7 @@ HdSt_ApplyMaterialXFilter(
 
         // Load Standard Libraries/setup SearchPaths (for mxDoc and mxShaderGen)
         mx::FilePathVec libraryFolders;
-        mx::FileSearchPath searchPath;
-        searchPath.append(mx::FilePath(PXR_MATERIALX_STDLIB_DIR));
+        mx::FileSearchPath searchPath = HdMtlxSearchPaths();
         mx::DocumentPtr stdLibraries = mx::createDocument();
         mx::loadLibraries(libraryFolders, searchPath, stdLibraries);
 

pxr/usd/plugin/usdMtlx/discovery.cpp

@@ -185,8 +185,10 @@ class UsdMtlxDiscoveryPlugin : public NdrDiscoveryPlugin {
 
 UsdMtlxDiscoveryPlugin::UsdMtlxDiscoveryPlugin()
 {
+    // Note this is the same envar used in HdMtlxSearchPaths(). This is used to 
+    // indicate the location of any additional custom mtlx files.
     static const auto searchPaths =
-        UsdMtlxGetSearchPathsFromEnvVar("PXR_USDMTLX_PLUGIN_SEARCH_PATHS");
+        UsdMtlxGetSearchPathsFromEnvVar("PXR_MTLX_PLUGIN_SEARCH_PATHS");
 
     _searchPaths = searchPaths;
     _allSearchPaths =

pxr/usd/plugin/usdMtlx/testenv/testUsdMtlxDiscovery.py

@@ -23,7 +23,7 @@
 # language governing permissions and limitations under the Apache License.
 
 import os
-os.environ['PXR_USDMTLX_PLUGIN_SEARCH_PATHS'] = os.getcwd()
+os.environ['PXR_MTLX_PLUGIN_SEARCH_PATHS'] = os.getcwd()
 
 from pxr import Tf, Ndr, Sdr
 import unittest

pxr/usd/plugin/usdMtlx/testenv/testUsdMtlxParser.py

@@ -23,7 +23,7 @@
 # language governing permissions and limitations under the Apache License.
 
 import os
-os.environ['PXR_USDMTLX_STDLIB_SEARCH_PATHS'] = os.getcwd()
+os.environ['PXR_MTLX_STDLIB_SEARCH_PATHS'] = os.getcwd()
 
 from pxr import Tf, Sdr
 import unittest

pxr/usd/plugin/usdMtlx/utils.cpp

@@ -200,7 +200,10 @@ UsdMtlxStandardLibraryPaths()
 {
     static const auto materialxLibraryPaths =
         UsdMtlxMergeSearchPaths(
-            UsdMtlxGetSearchPathsFromEnvVar("PXR_USDMTLX_STDLIB_SEARCH_PATHS"),
+            // Note this is the same envar used in HdMtlxSearchPaths() 
+            // This is used to indicate the location of the MaterialX/libraries
+            // folder if moved/changed from the path in PXR_MATERIALX_STDLIB_DIR
+            UsdMtlxGetSearchPathsFromEnvVar("PXR_MTLX_STDLIB_SEARCH_PATHS"),
             NdrStringVec{
 #ifdef PXR_MATERIALX_STDLIB_DIR
                 PXR_MATERIALX_STDLIB_DIR

third_party/renderman-24/plugin/hdPrman/CMakeLists.txt

@@ -22,9 +22,6 @@ endif()
 set(optionalIncludeDirs "")
 set(optionalPublicClasses "")
 if (${PXR_ENABLE_MATERIALX_SUPPORT})
-    add_definitions(-DPXR_MATERIALX_STDLIB_DIR="${MATERIALX_STDLIB_DIR}")
-    add_definitions(-DPXR_MATERIALX_BASE_DIR="${MATERIALX_BASE_DIR}")
-
     list(APPEND optionalLibs ${MATERIALX_LIBRARIES} hdMtlx)
     list(APPEND optionalIncludeDirs ${MATERIALX_INCLUDE_DIRS})
     list(APPEND optionalPublicClasses matfiltMaterialX)

third_party/renderman-24/plugin/hdPrman/matfiltMaterialX.cpp

@@ -621,10 +621,8 @@ MatfiltMaterialX(
         if (!terminalNode->inputConnections.empty()) {
 
             // Load Standard Libraries/setup SearchPaths (for mxDoc and mxShaderGen)
-            mx::FilePathVec libraryFolders = { "libraries", };
-            mx::FileSearchPath searchPath;
-            searchPath.append(mx::FilePath(PXR_MATERIALX_STDLIB_DIR));
-            searchPath.append(mx::FilePath(PXR_MATERIALX_BASE_DIR));
+            mx::FilePathVec libraryFolders;
+            mx::FileSearchPath searchPath = HdMtlxSearchPaths();
             mx::DocumentPtr stdLibraries = mx::createDocument();
             mx::loadLibraries(libraryFolders, searchPath, stdLibraries);