City GML to 3D Tiles

Deven Mistry -- 08/16/2022

Cesium Ion does not allow you to directly the rendered 3D tiles which are obtained from the CityGML. As an alternative to that, this task was explored.

citygml-to-3dtiles

This repo was found by Sudhir. Link to the repo.

The repository is a npm package which allows you convert CityGML files to 3D Tiles.

Install

To install the package follow the instructions on the README of the repository.

Adding a new CRS

JS -- 08/22/2023 -- modified for clarity...

1. Once the npm package is installed, you can run the CLI tool.
2. The CityGML have we are using for Absecon Island and Martin County contain a CRS which is not directly supported by the tool.
3. You need to add a custom CRS to the source code of the tool
4. Open the source code at C:\Users\<USER>\AppData\Roaming\npm\node_modules\citygml-to-3dtiles.
5. Open bin\citygml-to-3dtiles.mjs and modify the Converter constructor to match the following:

   let converter = new Converter({
      srsProjections: {
         "urn:ogc:def:crs:EPSG::4979": "+proj=longlat +datum=WGS84 +no_defs +type=crs",
         "EPSG:4979": "+proj=longlat +datum=WGS84 +no_defs +type=crs"
      }
   })
6. Additional instructions on where the appropriate syntax and other nuances are available in the README of the citygml-to-3dtiles repository.

Uploading the tileset to Cesium Ion

1. Once you have the 3D Tiles, you can upload them to Cesium Ion.
2. The tool creates 2 files, tileset.json and a full.b3dm file.
3. You cannot upload these 2 files individually, you need to zip file them and then upload them to Ion.