vsgCs Usage

JSON World files

vsgCs and the worldviwer program can read a simple JSON description of the tilesets and overlays to include in a scene. The simplest example is tests/csterrain.json:

{  "Type": "World",
   "tilesets": [
       {
       "Type": "Tileset",
       "ionAssetID":1,
       "overlays": [
           {
           "Type": "IonRasterOverlay",
           "assetId": 2
       }
       ]
   }
   ]
} 

This file specifies that the Cesium World Terrain will be draped with Bing imagery. These assets will be streamed (or forwarded) from the Cesium ion server.

See the tests directory for examples. These include:

• csterrain.json Cesium World Terrain with Bing images
• color-debug-overlay.json Debugging layer shows tile extents
• multilayer.json Multiple layers
• osm-buildings.json The world with OSM buildings. This is an example of multiple tilesets being displayed together, with Bing imagery projected on the buildings too.
• osm-nooverlay.json OSM buildings without the Bing overlay, so that the colors from the cesium#color feature attribute are used to shade the buildings.
• agi.json The ion tutorial tileset
• GMaps-ion.json Google Photorealistic 3D Tiles provisioned by Cesium ion

Cesium ion

Unless you have your own 3D Tiles tilesets, you will need to stream content from Cesium ion, so create and account there if you need to. Do the tutorial for creating a 3D tile if you want. Your "My Assets" page will look something like:

vsgCs uses the asset IDs in the left column to stream data from Cesium ion. The assets with type "Imagery" can't be used on their own; they must be draped over a tileset. Asset 1, "Cesium World Terrain", is a tileset with only elevation data, so must be used with an overlay to be useful.

Access token

Any interaction with a Cesium ion server requires an access token. On the "Access Tokens" page of Cesium ion, copy your token. while it can be passed on the command line to worldviewer, it is more convenient to store it in a file e.g., .cesiumiontoken in your home directory.

worldviewer

The worldviewer program demonstrates the basic features of vsgCs. To view the world file shown above:

worldviewer --ion-token-file ~/.cesiumiontoken vsgCs/tests/csterrain.json

which should produce:

worldviewer can take, as arguments, one .json file that defines a WorldNode, and then any number of additional tile set sources. These can either be a vsgCs .json that defines a TilesetNode object, or the location of an actual 3D Tiles tileset; the latter's URI should end in tileset.json. Any file that can be loaded by vsgXchange can also be specified, although it must contain a transform to place it on the globe.

Google Maps Photorealistic 3D Tiles

vsgCs renders 3D Tiles from Google's new Photorealistic Tiles service. The tileset description is simple -- GMaps-sample.json -- but you need a Google Maps API key, which I found complicated to create. My recommendation is to follow Cesium's Photorealistic Tiles tutorials; the process for creating an API key is the same as for Cesium's products. Then insert the key in GMaps-sample.json. An easier alternative is to use Cesium ion to automatically supply an API key. The Photorealistic Tiles are just another ion asset; see GMaps-ion.json for usage.

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