Light reference in the node

[Tugcga]

Describe the issue

When create GLTF file for the scene with lights, actual reference to the light does not assigned to the node.

To Reproduce

Minimal example with wrong output:

tinygltf::Model model;
tinygltf::Scene scene;

// setup the light
tinygltf::Light light;
light.name = "light";
light.type = "point";
light.intensity = 0.75;
light.color = std::vector<double>{1.0, 0.8, 0.95};

model.lights.push_back(light);

// setup the node
tinygltf::Node node;
node.name = "light_node";
// assign light to the node
node.light = 0;
// add to the model
model.nodes.push_back(node);
// and to the scene
scene.nodes.push_back(0);

scene.name = "scene_Name";
model.scenes.push_back(scene);
model.defaultScene = 0;

tinygltf::TinyGLTF gltf;
gltf.WriteGltfSceneToFile(&model, "output.gltf");

As a result it produce the following output.gltf:

{
  "asset": {
    "version": "2.0"
  },
  "extensions": {
    "KHR_lights_punctual": {
      "lights": [
        {
          "color": [
            1.0,
            0.8,
            0.95
          ],
          "intensity": 0.75,
          "name": "light",
          "type": "point"
        }
      ]
    }
  },
  "extensionsUsed": [
    "KHR_lights_punctual"
  ],
  "nodes": [
    {
      "extensions": {
        "KHR_lights_punctual": {}
      },
      "name": "light_node"
    }
  ],
  "scene": 0,
  "scenes": [
    {
      "name": "scene_Name",
      "nodes": [
        0
      ]
    }
  ]
}

Expected behaviour

The node with the name light_node should contains

"extensions": {
        "KHR_lights_punctual": {
          "light": 0
        }
      },

Possible solution

In the static void SerializeGltfNode(const Node &node, detail::json &o) function find the KHR_lights_punctual section in the json by using detail::FindMember(extensions, "KHR_lights_punctual", it); instead of detail::FindMember(o, "KHR_lights_punctual", it);

[syoyo]

Good find!

The spec says https://github.com/KhronosGroup/glTF/blob/main/extensions/2.0/Khronos/KHR_lights_punctual/README.md#adding-light-instances-to-nodes

So we need to list light ids in extensions.KHR_lights_punctual of node.

Probably we simply forget to serialize light ids to extensions.KHR_lights_punctual of node. PR is much appreciated!

[ptc-tgamper]

I screwed up the issue number in the commit message. This has been fixed by https://github.com/syoyo/tinygltf/pull/463

[syoyo]

Thank you @ptc-tgamper, close this issue as resolved.