diff --git a/cpp_header_codegen/cpp_header_codegen.cc b/cpp_header_codegen/cpp_header_codegen.cc
index 4ab63a5..e4368cf 100644
--- a/cpp_header_codegen/cpp_header_codegen.cc
+++ b/cpp_header_codegen/cpp_header_codegen.cc
@@ -5,6 +5,7 @@
 #include "ecsact/codegen/plugin.h"
 #include "ecsact/codegen/plugin.hh"
 #include "ecsact/lang-support/lang-cc.hh"
+#include "ecsact/cpp_codegen_plugin_util.hh"
 
 constexpr auto GENERATED_FILE_DISCLAIMER = R"(// GENERATED FILE - DO NOT EDIT
 )";
@@ -67,21 +68,23 @@ static auto cpp_field_type_name(ecsact_field_type field_type) -> std::string {
 }
 
 static void write_fields(
-	ecsact::codegen_plugin_context& ctx,
-	ecsact_composite_id             compo_id,
-	std::string_view                indentation
+	ecsact::codegen_plugin_context&                       ctx,
+	ecsact_composite_id                                   compo_id,
+	std::predicate<ecsact_field_type, const char*> auto&& filter,
+	std::string_view                                      indentation
 ) {
 	using ecsact::cc_lang_support::cpp_identifier;
 	using ecsact::cc_lang_support::cpp_type_str;
 	using namespace std::string_literals;
 
-	auto full_name =
-		ecsact_meta_decl_full_name(ecsact_id_cast<ecsact_decl_id>(compo_id));
-
 	for(auto field_id : get_field_ids(compo_id)) {
 		auto field_type = ecsact_meta_field_type(compo_id, field_id);
 		auto field_name = ecsact_meta_field_name(compo_id, field_id);
 
+		if(!filter(field_type, field_name)) {
+			continue;
+		}
+
 		ctx.writef(
 			"{}{} {}",
 			indentation,
@@ -94,7 +97,34 @@ static void write_fields(
 		}
 		ctx.writef(";\n");
 	}
+}
+
+static void for_each_field(
+	ecsact_composite_id                                   compo_id,
+	std::invocable<ecsact_field_type, const char*> auto&& fn
+) {
+	using ecsact::cc_lang_support::cpp_identifier;
+	using ecsact::cc_lang_support::cpp_type_str;
+	using namespace std::string_literals;
+
+	for(auto field_id : get_field_ids(compo_id)) {
+		auto field_type = ecsact_meta_field_type(compo_id, field_id);
+		auto field_name = ecsact_meta_field_name(compo_id, field_id);
+		fn(field_type, field_name);
+	}
+}
 
+static auto write_operators(
+	ecsact::codegen_plugin_context& ctx,
+	ecsact_composite_id             compo_id,
+	std::string_view                indentation
+) -> void {
+	using ecsact::cc_lang_support::cpp_identifier;
+	using ecsact::cc_lang_support::cpp_type_str;
+	using namespace std::string_literals;
+
+	auto full_name =
+		ecsact_meta_decl_full_name(ecsact_id_cast<ecsact_decl_id>(compo_id));
 	ctx.writef(
 		"{}auto operator<=>(const {}&) const = default;\n",
 		indentation,
@@ -158,6 +188,49 @@ static auto has_assoc_fields(CompositeID compo_id) -> bool {
 	return false;
 }
 
+template<typename CompositeID>
+static auto write_indexed_fields_struct(
+	ecsact::codegen_plugin_context& ctx,
+	CompositeID                     compo_id
+) -> void {
+	using ecsact::cpp_codegen_plugin_util::block;
+	using ecsact::cpp_codegen_plugin_util::method_printer;
+
+	ctx.writef("\n");
+	block(ctx, "struct IndexedFields", [&] {
+		write_fields(
+			ctx,
+			ecsact_id_cast<ecsact_composite_id>(compo_id),
+			[](ecsact_field_type type, const char*) -> bool {
+				return type.kind == ECSACT_TYPE_KIND_FIELD_INDEX;
+			},
+			"\t"
+		);
+
+		{
+			ctx.writef("constexpr static ");
+			auto _ = method_printer(ctx, "from_composite")
+								 .parameter("const auto&", "composite")
+								 .return_type("IndexedFields");
+
+			block(ctx, "return", [&] {
+				for_each_field(
+					ecsact_id_cast<ecsact_composite_id>(compo_id),
+					[&](ecsact_field_type type, const char* field_name) {
+						if(type.kind != ECSACT_TYPE_KIND_FIELD_INDEX) {
+							return;
+						}
+
+						ctx.writef("\t.{0} = composite.{0},\n", field_name);
+					}
+				);
+			});
+			ctx.writef(";\n");
+		}
+	});
+	ctx.writef(";\n");
+}
+
 void ecsact_codegen_plugin(
 	ecsact_package_id          package_id,
 	ecsact_codegen_write_fn_t  write_fn,
@@ -209,7 +282,12 @@ void ecsact_codegen_plugin(
 			has_assoc_fields(comp_id) ? "true" : "false"
 		);
 		write_constexpr_id(ctx, "ecsact_component_id", comp_id, "\t");
-		write_fields(ctx, compo_id, "\t"s);
+		ctx.indentation += 1;
+		write_indexed_fields_struct(ctx, comp_id);
+		ctx.indentation -= 1;
+		ctx.writef("\n");
+		write_fields(ctx, compo_id, [](auto, auto) { return true; }, "\t"s);
+		write_operators(ctx, compo_id, "\t"s);
 		ctx.writef("}};\n");
 	}
 
@@ -222,7 +300,12 @@ void ecsact_codegen_plugin(
 			has_assoc_fields(comp_id) ? "true" : "false"
 		);
 		write_constexpr_id(ctx, "ecsact_transient_id", comp_id, "\t");
-		write_fields(ctx, compo_id, "\t"s);
+		ctx.indentation += 1;
+		write_indexed_fields_struct(ctx, comp_id);
+		ctx.indentation -= 1;
+		ctx.writef("\n");
+		write_fields(ctx, compo_id, [](auto, auto) { return true; }, "\t"s);
+		write_operators(ctx, compo_id, "\t"s);
 		ctx.writef("}};\n");
 	}
 
@@ -238,7 +321,12 @@ void ecsact_codegen_plugin(
 			write_system_struct(ctx, child_system_id, "\t");
 		}
 		write_system_impl_decl(ctx, "\t");
-		write_fields(ctx, compo_id, "\t");
+		ctx.indentation += 1;
+		write_indexed_fields_struct(ctx, compo_id);
+		ctx.indentation -= 1;
+		ctx.writef("\n");
+		write_fields(ctx, compo_id, [](auto, auto) { return true; }, "\t");
+		write_operators(ctx, compo_id, "\t"s);
 		ctx.writef("}};\n");
 	}