README.md

SOM

A Scene Object Model (SOM) file lists all of the GLTF or GLB models to load into a Decentraland scene. This module contains a SceneObject data structure used to define the models and their positioning in the world, and a ModelLoader class that handles the loading and positioning at runtime.

SOM JSON data

The SOM data structure is defined in a file named som.ts.

Here's an example of a som.ts file for a scene with two hills and a rock:

{
  "scene": {
    "title": "My Great Scene",
    "hill01": {
      "filename": "terrain/hill.glb",
      "pos": [ 2, 14, 8 ],
      "angles": [ 0, 270, 0 ],
      "scale": [ 1.5, 1.5, 1.5 ]
    },
    "hill02": {
      "filename": "terrain/hill.glb",
      "pos": [ 12, 14, 8 ],
      "angles": [ 0, 270, 0 ],
      "scale": [ 1.5, 1.5, 1.5 ]
    },
    "rock01": {
      "filename": "rock.gltf",
      "pos": [ 7.3, 14.4, 2.2 ],
      "angles": [ 0, 150, 0 ],
      "scale": [ 0.25, 0.25, 0.25],
      "throwable": true,
      "rigidbody": true,
      "physics": {
        "mass": 1,
        "bounciness": 0.4,
        "velocity": [0, 0, 0]
      }
    }
  }
}

Note that if the same model file is referenced more than once, the ModelLoader will only load that model file once, and re-use the GLTFShape component for each instance of the model.

The "rock01" entry in the example shows that you can also add custom properties to any scene object. You can later customize the ModelLoader.spawnSceneObject() function to recognize and handle the custom properties as you see fit.

ModelLoader Class

The ModelLoader class will instantiate the required Entities and Components, given an object from the som.json file, and place them in the scene with the given position and rotation.

// instantiate the ModelLoader
const loader:ModelLoader = new ModelLoader();

// load the models and place them in the scene
const hill01:Entity = loader.spawnSceneObject(som.scene.hill01);
const hill02:Entity = loader.spawnSceneObject(som.scene.hill02);
const rock1:Entity = loader.spawnSceneObject(som.scene.rock1);

The ModelLoader.spawnSceneObject() function creates an Entity, loads the model file to create a GLTFShape, and then adds the Entity to the engine.