missing commit.

src/prim-reconstruct.cc

@@ -2097,8 +2097,37 @@ bool ReconstructGPrimProperties(
 
   for (const auto &prop : properties) {
     PARSE_SINGLE_TARGET_PATH_RELATION(table, prop, kMaterialBinding, gprim->materialBinding)
-    PARSE_SINGLE_TARGET_PATH_RELATION(table, prop, kMaterialBindingCollection, gprim->materialBindingCollection)
     PARSE_SINGLE_TARGET_PATH_RELATION(table, prop, kMaterialBindingPreview, gprim->materialBindingPreview)
+    // material:binding:collection
+    PARSE_SINGLE_TARGET_PATH_RELATION(table, prop, kMaterialBindingCollection, gprim->materialBindingCollection)
+    // material:binding:collection:NAME
+    if (startsWith(prop.first, kMaterialBindingCollection + std::string(":"))) {
+
+      if (table.count(prop.first)) { 
+         continue;
+      }
+
+      if (!prop.second.is_relationship()) { 
+        PUSH_ERROR_AND_RETURN(fmt::format("`{}` must be a Relationship", prop.first));
+      } 
+
+      std::string collection_name = removePrefix(prop.first, kMaterialBindingCollection + std::string(":"));
+      if (collection_name.empty()) {
+        PUSH_ERROR_AND_RETURN("empty NAME is not allowed for 'mateirial:binding:collection'");
+      }
+      std::vector<std::string> names = split(collection_name, ":");
+      if (names.size() > 1) {
+        PUSH_ERROR_AND_RETURN("Nested namespace is not allowed for 'mateirial:binding:collection'");
+      }
+      collection_name = names[0];
+
+      const Relationship &rel = prop.second.get_relationship();
+
+      gprim->add_materialBindingCollection(collection_name, rel);
+
+      table.insert(prop.first);
+      continue;
+    }
     PARSE_SINGLE_TARGET_PATH_RELATION(table, prop, kProxyPrim, gprim->proxyPrim)
     PARSE_TYPED_ATTRIBUTE(table, prop, "doubleSided", GPrim, gprim->doubleSided)
     PARSE_ENUM_PROPETY(table, prop, "visibility", VisibilityEnumHandler, GPrim,

src/usdGeom.hh

@@ -13,6 +13,7 @@
 #include "prim-types.hh"
 #include "value-types.hh"
 #include "xform.hh"
+#include "usdShade.hh"
 
 namespace tinyusdz {
 
@@ -288,7 +289,7 @@ struct GPrim : Xformable {
 
   // Some frequently used materialBindings
   nonstd::optional<Relationship> materialBinding; // material:binding
-  nonstd::optional<Relationship> materialBindingCollection; // material:binding:collection
+  nonstd::optional<Relationship> materialBindingCollection; // material:binding:collection  TODO: deprecate?(seems `material:binding:collection` without leaf NAME seems ignored in pxrUSD.
   nonstd::optional<Relationship> materialBindingPreview; // material:binding:preview
 
   std::map<std::string, Property> props;
@@ -369,6 +370,75 @@ struct GPrim : Xformable {
     return meta;
   }
 
+  bool has_materialBinding() const {
+    return materialBinding.has_value();
+  }
+
+  bool has_materialBindingPreview() const {
+    return materialBindingPreview.has_value();
+  }
+
+  void clear_materialBinding() {
+    materialBinding.reset();
+  }
+
+  void clear_materialBindingPreview() {
+    materialBindingPreview.reset();
+  }
+
+  void set_materialBinding(const Relationship &rel) {
+    materialBinding = rel;
+  }
+
+  void set_materialBinding(const Relationship &rel, const MaterialBindingStrength strength) {
+    value::token strength_tok(to_string(strength));
+    materialBinding = rel;
+    materialBinding.value().metas().bindMaterialAs = strength_tok;
+  }
+
+  void set_materialBindingPreview(const Relationship &rel) {
+    materialBindingPreview = rel;
+  }
+
+  void set_materialBindingPreview(const Relationship &rel, const MaterialBindingStrength strength) {
+    value::token strength_tok(to_string(strength));
+    materialBindingPreview = rel;
+    materialBindingPreview.value().metas().bindMaterialAs = strength_tok;
+  }
+
+  bool has_materialBindingCollection(const std::string &tok) {
+    return _materialBindingCollectionMap.count(tok);
+  }
+
+  void add_materialBindingCollection(const std::string &tok, const Relationship &rel) {
+
+    // NOTE:
+    // https://openusd.org/release/wp_usdshade.html#basic-proposal-for-collection-based-assignment
+    // says: material:binding:collection defines a namespace of binding relationships to be applied in namespace order, with the earliest ordered binding relationship the strongest
+    //
+    // so the app is better first check if `tok` element alreasy exists(using has_materialBindingCollection)
+
+    _materialBindingCollectionMap[tok] = rel;
+  }
+
+  void clear_materialBindingCollection(const std::string &tok) {
+
+    _materialBindingCollectionMap.erase(tok);
+  }
+
+  void add_materialBindingCollection(const std::string &tok, const Relationship &rel, MaterialBindingStrength strength) {
+    value::token strength_tok(to_string(strength));
+
+    _materialBindingCollectionMap[tok] = rel;
+    _materialBindingCollectionMap[tok].metas().bindMaterialAs = strength_tok;
+
+  }
+
+  const std::map<std::string, Relationship> materialBindingCollectionMap() const {
+    return _materialBindingCollectionMap;
+  }
+
+
  private:
 
   //bool _valid{true};  // default behavior is valid(allow empty GPrim)
@@ -379,6 +449,9 @@ struct GPrim : Xformable {
   // For Variants
   std::map<std::string, VariantSet> _variantSetMap;
 
+  // For material:binding:collection:<NAME>
+  std::map<std::string, Relationship> _materialBindingCollectionMap;
+
 };
 
 struct Xform : GPrim {

src/usdShade.hh

@@ -41,6 +41,26 @@ constexpr auto kUsdPrimvarReader_matrix = "UsdPrimvarReader_matrix";
 constexpr auto kWeaderThanDescendants = "weakerThanDescendants";
 constexpr auto kStrongerThanDescendants = "strongerThanDescendants";
 
+enum class MaterialBindingStrength
+{
+  WeakerThanDescendants, // default
+  StrongerThanDescendants
+};
+
+// TODO: Move to pprinter.hh?
+static std::string to_string(const MaterialBindingStrength strength) {
+  switch (strength) {
+    case MaterialBindingStrength::WeakerThanDescendants: {
+      return kWeaderThanDescendants;
+    }
+    case MaterialBindingStrength::StrongerThanDescendants: {
+      return kStrongerThanDescendants;
+    }
+  }
+
+  return "[[Invalid MaterialBindingStrength]]";
+}
+
 // TODO: Inherit from Prim?
 struct UsdShadePrim {
   std::string name;