7.1. The Scene Pipeline

The scene pipeline supports the export of scenes from 3D modeling packages via Collada.

For a given Collada scene the dae2json tool will export the following elements:

• Shapes
• Materials
• Effects
• Images
• Physics models
• Physics materials
• Physics bodies
• Animations
• Lights
• Cameras
• Nodes hierarchy

Materials, effects and lights can be overloaded at this stage or later at runtime. The dae2json tool supports passing include files that provide material, effect and light overloads. Overloads from the include files will be matched by name and will replace the elements from the Collada scene.

This is an example of how a JSON include file would look::

{
  "version": 1,
  "lights":
  {
    "point_light_1":
    {
      "type": "point",
      "color": [1, 1, 1],
      "material": "squarelight",
      "halfextents": [10, 20, 10]
    },
    "spot_light_1":
    {
      "type: "spot",
      "color": [0.89, 1, 0.99],
      "material": "conelight",
      "right": [0, 6, 26],
      "up": [21, 0, 0],
      "target": [0, -36, 9],
      "shadows": true
    }
    "directional_light":
    {
      "type": "directional",
      "color": [0.2, 0.2, 0.8],
      "direction": [0, -1, 0],
      "global": true
    },
    "red_ambient":
    {
      "type": "ambient",
      "color": [0.1, 0, 0],
      "global": true
    },
  },
  "effects":
  {
    "lambert-fx":
    {
      "type": "lambert",
      "meta":
      {
        "normals": true
      }
    }
  },
  "materials":
  {
    "squarelight":
    {
      "parameters":
      {
        "lightfalloff": "squarelight.dds",
        "lightprojection": "squarelight.dds"
      }
    },
    "conelight":
    {
      "parameters":
      {
        "lightfalloff": "white",
        "lightprojection": "roundlight.jpg"
      }
    },
    "rocket_colored":
    {
      "effect": "lambert-fx",
      "parameters":
      {
        "color": [1, 0.2, 0, 0.5],
        "diffuse": "textures/rocket.dds"
      },
      "meta":
      {
        "collisionFilter": [ "ALL" ],
        "noshadows": true,
        "transparent": true,
        "materialcolor": true
      }
    }
  },
}

These include files can be generated by hand or exported from other source assets, a Collada scene file can be exported passing as many of them as needed as parameters to the tool.

The dae2json tool automatically converts Collada scenes to have 1 unit per meter and the Y vector to point upwards, some modeling packages may use different conventions.

For details on generating your own JSON files see the Turbulenz Engine JSON formats documentation.

7.1.1. Workflow

• Model scene in 3D modeling package
• Export scenes to Collada (one or more Collada scene files)
• Create include files with an editor supporting JSON or JavaScript
• Execute dae2json on each Collada file, include files if required
• Load converted scenes into user application

7.1.2. Collada feature limitations

Certain features supported in the Collada specification are not supported or have limited support, these limitations are documented below.

• instance_node with internal url - An instance_node in a Collada scene will be correctly inserted into the converted scene but will have been de-instanced. As a result any operations made to the source node at runtime will not be propagated automatically to its instances.
• instance_node with external url - References to other Collada scene files will be inserted into the converted scene and the whole external hierarchy will be de-instanced at runtime. This may not be the required result if the reference was not linking to the root node of the external scene.