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A CLT task serves .clt tile packages produced by CesiumLab. The .clt format is a SQLite database where each tile is stored as a binary blob keyed by its path. WebPublish opens the database and exposes a tile endpoint that CesiumLab and compatible clients can consume directly.

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How it works

When a request arrives at http://127.0.0.1:9090/{taskId}/{tilepath}, WebPublish looks up the value of {tilepath} in the SQLite tiles table and returns the stored tile data. The query used is: 
SELECT tile, type FROM tiles WHERE path = '{tilepath}'
Tiles typed as json are returned with a application/json content type. All other tiles are returned as application/octet-stream. Tiles stored with gzip encoding are forwarded with a Content-Encoding: gzip header. If no tile is found for the requested path, WebPublish returns a 404 response.

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Endpoint

http://127.0.0.1:9090/{taskId}/{tilepath}
The {tilepath} corresponds to the path column in the tiles table of the .clt file. Example: 
http://127.0.0.1:9090/myterrain/tileset.json
http://127.0.0.1:9090/myterrain/0/0/0.terrain
The tileset entry point (for most CesiumLab packages) is tileset.json: 
http://127.0.0.1:9090/{taskId}/tileset.json

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Creating a CLT task

1

Open the new task dialog

Click Add (or +) in the toolbar.
2

Select the CLT type

In the Type field, choose CLT.
3

Choose the .clt file

Click Browse next to the Path field and select the .clt file on your machine.
The .clt file must be a valid SQLite database with a tiles table containing path, tile, and type columns. Files exported directly from CesiumLab meet this requirement.
4

Set the task ID and name

Enter a short ID (for example, terrain). The tileset will be accessible at:
http://127.0.0.1:9090/terrain/tileset.json
5

Save and start

Click OK to save the task, then click Start to enable it.

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Loading the tileset in CesiumLab

To view the published tileset in a CesiumLab viewer, use the local WebPublish URL as the tileset source. In a CesiumJS application, add the tileset using the URL of the tileset.json endpoint: 
const tileset = await Cesium.Cesium3DTileset.fromUrl(
  'http://127.0.0.1:9090/{taskId}/tileset.json'
);
viewer.scene.primitives.add(tileset);
viewer.zoomTo(tileset);
Replace {taskId} with the ID you assigned when creating the task.
If you are loading the tileset in a browser-based CesiumJS application served from a different origin, the proxy task is an alternative approach for adding CORS headers to your tileset responses. See the Proxy task for details.

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Gzip compression

Tiles in .clt packages are typically stored in gzip-compressed form. WebPublish passes gzip-compressed tiles through to the client with a Content-Encoding: gzip header, provided the client’s Accept-Encoding header includes gzip. Clients that do not advertise gzip support receive decompressed tile data.

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Notes

  • The task is automatically disabled if the .clt file cannot be opened. Update the Path in the task settings and re-enable the task if you move or replace the file.
  • The CLT task does not currently support an interactive map preview. Use CesiumLab or a CesiumJS application to visualize the data.
  • Each incoming tile request increments the task’s Data used counter by one request. Use the Data limit field to cap the total number of requests served.

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