Ga naar inhoud

Layers in Netherlands3D


Layers in Netherlands3D are objects that have an effect on the 3D environment. Layers are hierarchical, similar to GameObjects in Unity. Because of this. the Layer data structure makes use of Unity's GameObject/Transform hierarchy in order to minimize custom coding of the data structure, and to visualize the data structure in the Unity Editor hierarchy.

Functionality of layers

All layers have the following basic functionality:

  • Parenting: This works similar to the Unity Hierarchy.
  • Reordering: This works similar to changing the sibling index within the same parent in the Unity hierarchy.
  • Visibility: This works similar to setting a GameObject active/inactive in the Unity hierarchy.
  • Properties: Each layer can have its own settings specific to the layer type, or even more specific to the content of the layer. This is similar to how the inspector in Unity will display all components and serialized fields of a GameObject.

The layer data structure hierarchy is managed by the class LayerData. There should only be 1 LayerData object in the scene.

Layer types

Layers are split in 2 categories:

  1. Regular layers that do not need their own GameObject hierarchy (basic layers)
  2. Layers that do require a GameObject hierarchy (referenced layers)

Basic layers

The first category of layers is the most simple. These layers are an extension of the LayerNL3DBase class.

Folder layer:

The most simple form of a Layer in this category is a FolderLayer. This layers has no functionality, except for providing the user with a way to organise other layers. It is similar to an empty GameObject.

Polygon selection layer:

A PolygonSelectionLayer is a layer that represents a polygon in the 3D environment. This layer can be created by providing a List<Vector3> of points (either by user input or from another source). This will create a layer in the hierarchy, with a visualisation that will listen to user input so that the layer can be selected by the user by clicking on the visualisation in the scene.

Referenced layers

In case a layer has an internal hierarchy (such as a hierarchy of object parts, or a container with different tile objects) a layer can be integrated in the layer system as a referenced layer. A referenced layer exists outside of the Layer data structure, but has a connection to it through a ReferencedProxyLayer . The ReferencedProxyLayer will pass the required actions that affect the layer to its reference outside of the layer hierarchy, thereby making the referenced layer comply with the layer functionalities.

In order to do this, the layer object outside of the hierarchy must have an extension of the abstract class ReferencedLayer attached to it. This class will automatically create the ReferencedProxyLayer, thereby creating the connection to the layer system.

The following Layers are referenced layers:

Hierarchical object layer:

A HierarchicalObjectLayer is an object that can be placed in the 3D environment. By default, this object can be moved by the transform handles. Objects of this type either come from a library of developer defined objects, or by user uploads. The most simple Hierarchical object layer is a GameObject with a MeshFilter, MeshRenderer, Collider, and HierarchicalObjectLayer component attached. More complex Hierarchical object layers can have nested GameObjects with each their own internal logic.

Cartesian tile layer:

A CartesianTileLayer is a layer that makes use of the Netherlands3D custom tile file format. The objects and tiles in the layer are managed by the TileHandler and through the class CartesianTileLayer can interact with the layer system. For more information see the section on Cartesian Tiles.

3D tile layer:

A Tile3DLayer2 is a layer that makes use of the 3D Tiles file format. These layers are managed by Read3DTileset and through the class Tile3DLayer2 can interact with the layer system. For more information see the section on 3D Tiles.

Object scatter layer:

An ObjectScatterLayer is a special type of layer that will scatter the combined mesh of a HierarchicalObjectLayer in the area defined by a PolygonLayer. To do this, create a PolygonLayer and make a HierarchicalObjectLayer the child of the PolygonLayer. This will convert the HierarchicalObjectLayer to an ObjectScatterLayer. Unparenting the ObjectScatterLayer from a PolygonLayer will revert the layer back to a HierarchicalObjectLayer. The ObjectScatterLayer has scatter settings that determine how the scattering should occur.


The scattering is achieved through GPUInstancing, and therefore the mesh and material should support this. All objects in the ObjectLibrary support scattering.

Layer UI

Each Layer can have an associated UI component defined by the class LayerUI. This component controls the UI elements associated with the layer. Interacting with the LayerUI will affect the corresponding LayerNL3DBase. The Layer UI hierarcy is managed by LayerManager. This class holds a references to the layer type icons that are requested by LayerUI.

Creating your own layers of an existing type

In order to add one of your own layers as an option through the existing UI, the following steps should be followed:

  1. Create a prefab with the layer object. Make sure this object has a component of either LayerNL3DBase or ReferencedLayer attached to it.
  2. Instantiate the prefab. If this is done in the existing LayerPanel UI, add a button or toggle in the prefab AddLayerPanel.prefab in the appropriate panel sub section. Then have the script that controls the button or toggle logic instantiate the prefab made in step 1.

Creating your own layers of a new type

Follow the following steps to create a new layer type:

  1. Choose if the new layer type can be a simple layer (direct extension of LayerNL3DBase) or it needs to be a more complex referenced layer (extension of ReferencedLayer).
  2. Extend the chosen class and implement the required methods.
  3. Add your own logic to the new class
  4. Add a reference to the appropriate type and icon in LayerManager to ensure the new layer does not use the default ? icon.

Layers and Functionalities

Specific layers or specific types of layers can also be enabled/disabled with the functionalities system. Follow these steps to do this:

  1. Add a FunctionalityListener to the prefab of the layer. Add the functionality you want to link the layer to, and in the OnDisableFunctionality event, add a function that will destroy the gameObject itself. This will clean up any active layers when disabling the functionality.
  2. For any buttons that instantiate the prefab above, add a FunctionalityListener to the button that will enable/disable the button's gameObject when the functionality is enabled/disabled respectively. This will ensure the user cannot instantiate layers from functionalities that are disabled.
  3. (Optional) In case your layers should by default spawn when the functionality is enabled, add a PrefabSpawner script to the scene where the functionality and the associated prefab are set in the inspector.