Fix Empty scenes are wrongly serialized as null Issue #464

tests/tester.cc

@@ -756,34 +756,83 @@ TEST_CASE("load-issue-416-model", "[issue-416]") {
   REQUIRE(true == ret);
 }
 
-TEST_CASE("serialize-light-index", "[issue-457]") {
-  tinygltf::Model model;
-  tinygltf::Scene scene;
+TEST_CASE("serialize-empty-node", "[issue-457]") {
+  tinygltf::Model m;
+  // Add default constructed node to model
+  m.nodes.push_back({});
+  // Add scene to model
+  m.scenes.push_back({});
+  // The scene's only node is the empty node
+  m.scenes.front().nodes.push_back(0);
+
+  // Serialize model to output stream
+  std::stringstream os;
+  tinygltf::TinyGLTF ctx;
+  bool ret = ctx.WriteGltfSceneToStream(&m, os, false, false);
+  REQUIRE(true == ret);
+
+  // Parse serialized model
+  nlohmann::json j = nlohmann::json::parse(os.str());
+
+  // Serialized nodes shall hold an empty object that
+  // represents the default constructed node
+  REQUIRE(j.find("nodes") != j.end());
+  REQUIRE(j["nodes"].is_array());
+  REQUIRE(1 == j["nodes"].size());
+  CHECK(j["nodes"][0].is_object());
+  CHECK(j["nodes"][0].empty());
+
+  // We also want to make sure that the serialized scene
+  // is referencing the empty node.
+
+  // There shall be a single serialized scene
+  auto scenes = j.find("scenes");
+  REQUIRE(scenes != j.end());
+  REQUIRE(scenes->is_array());
+  REQUIRE(1 == scenes->size());
+  auto scene = scenes->at(0);
+  REQUIRE(scene.is_object());
+  // The scene's nodes array shall hold a reference
+  // to the single node
+  auto nodes = scene.find("nodes");
+  REQUIRE(nodes != scene.end());
+  REQUIRE(nodes->is_array());
+  REQUIRE(1 == nodes->size());
+  auto node = nodes->at(0);
+  CHECK(node.is_number_integer());
+  int idx = -1;
+  node.get_to(idx);
+  CHECK(0 == idx);
+}
+
+TEST_CASE("serialize-light-index", "[issue-458]") {
 
   // Create the light
   tinygltf::Light light;
   light.type = "point";
   light.intensity = 0.75;
   light.color = std::vector<double>{1.0, 0.8, 0.95};
-  // Add the light to the model
-  model.lights.push_back(light);
-  // Create a node that uses the light
-  tinygltf::Node node;
-  node.light = 0;
-  // Add the node to the model
-  model.nodes.push_back(node);
-  // Add the node to the scene
-  scene.nodes.push_back(0);
-  // Add the scene to the model
-  model.scenes.push_back(scene);
 
   // Stream to serialize to
   std::stringstream os;
 
   {
+    tinygltf::Model m;
+    tinygltf::Scene scene;
+    // Add the light to the model
+    m.lights.push_back(light);
+    // Create a node that uses the light
+    tinygltf::Node node;
+    node.light = 0;
+    // Add the node to the model
+    m.nodes.push_back(node);
+    // Add the node to the scene
+    scene.nodes.push_back(0);
+    // Add the scene to the model
+    m.scenes.push_back(scene);
     // Serialize model to output stream
     tinygltf::TinyGLTF ctx;
-    bool ret = ctx.WriteGltfSceneToStream(&model, os, false, false);
+    bool ret = ctx.WriteGltfSceneToStream(&m, os, false, false);
     REQUIRE(true == ret);
   }
 
@@ -794,11 +843,11 @@ TEST_CASE("serialize-light-index", "[issue-457]") {
     bool ok = ctx.LoadASCIIFromString(&m, nullptr, nullptr, os.str().c_str(), os.str().size(), "");
     REQUIRE(true == ok);
     // Check if the light was correctly serialized
-    REQUIRE(1 == model.lights.size());
-    CHECK(model.lights[0] == light);
+    REQUIRE(1 == m.lights.size());
+    CHECK(m.lights[0] == light);
     // Check that the node properly references the light
-    REQUIRE(1 == model.nodes.size());
-    CHECK(model.nodes[0].light == 0);
+    REQUIRE(1 == m.nodes.size());
+    CHECK(m.nodes[0].light == 0);
   }
 }
 
@@ -826,51 +875,30 @@ TEST_CASE("default-material", "[issue-459]") {
   CHECK(mat.emissiveTexture.index == -1);
 }
 
-TEST_CASE("serialize-empty-node", "[issue-457]") {
-  tinygltf::Model m;
-  // Add default constructed node to model
-  m.nodes.push_back({});
-  // Add scene to model
-  m.scenes.push_back({});
-  // The scene's only node is the empty node
-  m.scenes.front().nodes.push_back(0);
-
-  // Serialize model to output stream
+TEST_CASE("serialize-empty-scene", "[issue-464]") {
+  // Stream to serialize to
   std::stringstream os;
-  tinygltf::TinyGLTF ctx;
-  bool ret = ctx.WriteGltfSceneToStream(&m, os, false, false);
-  REQUIRE(true == ret);
 
-  // Parse serialized model
-  nlohmann::json j = nlohmann::json::parse(os.str());
-
-  // Serialized nodes shall hold an empty object that
-  // represents the default constructed node
-  REQUIRE(j.find("nodes") != j.end());
-  REQUIRE(j["nodes"].is_array());
-  REQUIRE(1 == j["nodes"].size());
-  CHECK(j["nodes"][0].is_object());
-  CHECK(j["nodes"][0].empty());
-
-  // We also want to make sure that the serialized scene
-  // is referencing the empty node.
+  {
+    tinygltf::Model m;
+    // Add empty scene to the model
+    m.scenes.push_back({});
+    // Serialize model to output stream
+    tinygltf::TinyGLTF ctx;
+    bool ret = ctx.WriteGltfSceneToStream(&m, os, false, false);
+    REQUIRE(true == ret);
+  }
 
-  // There shall be a single serialized scene
-  auto scenes = j.find("scenes");
-  REQUIRE(scenes != j.end());
-  REQUIRE(scenes->is_array());
-  REQUIRE(1 == scenes->size());
-  auto scene = scenes->at(0);
-  REQUIRE(scene.is_object());
-  // The scene's nodes array shall hold a reference
-  // to the single node
-  auto nodes = scene.find("nodes");
-  REQUIRE(nodes != scene.end());
-  REQUIRE(nodes->is_array());
-  REQUIRE(1 == nodes->size());
-  auto node = nodes->at(0);
-  CHECK(node.is_number_integer());
-  int idx = -1;
-  node.get_to(idx);
-  CHECK(0 == idx);
+  {
+    tinygltf::Model m;
+    tinygltf::TinyGLTF ctx;
+    // Parse the serialized model
+    bool ok = ctx.LoadASCIIFromString(&m, nullptr, nullptr, os.str().c_str(), os.str().size(), "");
+    REQUIRE(true == ok);
+    // Make sure the empty scene is there
+    REQUIRE(1 == m.scenes.size());
+    tinygltf::Scene scene{};
+    // Check that the scene is empty
+    CHECK(m.scenes[0] == scene);
+  }
 }

tiny_gltf.h

@@ -8063,6 +8063,15 @@ static void SerializeGltfModel(const Model *model, detail::json &o) {
     for (unsigned int i = 0; i < model->scenes.size(); ++i) {
       detail::json currentScene;
       SerializeGltfScene(model->scenes[i], currentScene);
+      if (detail::JsonIsNull(currentScene)) {
+        // Issue 464.
+        // `scene` does not have any required parameters,
+        // so the result may be null(unmodified) when all scene parameters
+        // have default value.
+        //
+        // null is not allowed thus we create an empty JSON object.
+        detail::JsonSetObject(currentScene);
+      }
       detail::JsonPushBack(scenes, std::move(currentScene));
     }
     detail::JsonAddMember(o, "scenes", std::move(scenes));