Freestanding Mode

As of version 7.20, the WWT WebGL engine supports a “freestanding mode” that allows it to run in a purely self-contained fashion — it will not make any requests to the worldwidetelescope.org servers for supporting data. This disables a number of the engine’s capabilities, but may be of interest for WWT adopters who are unwilling or unable to depend on external services.

Limitations of Freestanding Mode🔗

Activating the freestanding mode causes the engine to be limited in the following ways:

  • No default sky map. WWT’s built-in DSS sky map will not be available. The sky view will only be able to show an empty, black sky unless you import your own all-sky survey(s).
  • No built-in image sets. Likewise, WWT’s built-in database of all-sky maps and “study” images will not be available. If you wish to show any surveys or studies, you must load them in yourself.
  • No 3D “solar system” mode. The engine won't prevent you from activating this mode, but it will be virtually useless. Many aspects of this mode rely on WWT APIs, including:
    • COSMOS galaxies database
    • Hipparcos star database
    • Minor planets database
    • Planet and moon textures
  • Most tours will not work. If a tour relies on assets provided by the core WWT APIs, they will not have been loaded and will be missing. If you construct a tour that does not rely on these assets, it will work as expected.
  • No automatic proxying. When fetching web resources, if the WWT engine runs into a problem that seems to be due to HTTP/HTTPS mismatches or CORS restrictions, it will reroute the relevant requests through a proxy service on worldwidetelescope.org that works around the issue(s). In freestanding mode, this behavior is disabled.
  • No constellation artwork. These images are pulled from a WWT web API.
  • No ISS (International Space Station) coordinate frame or 3D model. WWT’s support for showing the ISS depends on web APIs to provide its current orbital parameters and a 3D model, so this support must be disabled in freestanding mode.
  • Tour URLs in WTML folders must be specified. In the standard mode, references to tours can be resolved to a URL that fetches their data based on a UUID registered with the WWT webservice. This is not possible in freestanding mode.
  • No automatic ID-based thumbnail images for tours. As above. These will use a generic star thumbnail image instead.
  • No automatic name-based thumbnail images for Places in WTML folders. These will use a generic star thumbnail image instead.
  • No automatic Bing-based DEM data for Mercator projection imagesets. Some Earth data have elevation data automatically attached. This feature will be deactivated.

Activating Freestanding Mode🔗

If you are using WWT in the Vue/Pinia component model, activate freestanding mode by specifying the Vue prop wwt-freestanding-asset-baseurl:

<template>
  <div>
    <WorldWideTelescope
      id="wwt"
      wwt-freestanding-asset-baseurl="https://myassets.org/wwtengine"
    ></WorldWideTelescope>
    <div id="my-ui-controls">...</div>
  </div>
</template>

This value is a base URL that will be used to look up simple, static data assets used by the engine. The default value used in the production version of WWT is https://web.wwtassets.org/engine/assets, and you can use that value here if you don’t mind depending on wwtassets.org.

If you're using the bundled TypeScript model, you can activate the mode with an analogous parameter, InitControlSettings#freestandingAssetBaseurl, when calling the WWTInstance constructor provided in the @wwtelescope/engine-helpers package.

Finally, at the lowest levels of abstraction, such as what you would have in the hosted JavaScript model, you can call the freestandingMode() method on the WWTControlBuilder class exported in the @wwtelescope/engine package. Once again, this API takes the same asset baseurl parameter as seen above.

Engine Assets🔗

Currently, the engine assets are not indexed elsewhere. To serve up your own assets, download the following files from the default baseurl given above:

  • callisto.png
  • circle.png
  • ConstellationNamePositions_EN.txt
  • constellations.txt
  • earth.png
  • europa.png
  • figures.txt
  • ganymede.png
  • glyphs1.png
  • glyphs1.xml
  • io.png
  • jupiter.png
  • mars.png
  • mercury.png
  • moon.png
  • moons.txt
  • moonshadow.png
  • neptune.png
  • pins.png
  • pluto.png
  • saturn.png
  • StarProfileAlpha.png
  • sun.png
  • sunCorona.png
  • thumb_folder.jpg
  • thumb_folderup.jpg
  • thumb_star.jpg
  • uranus.png
  • venus.png

The following assets are only used in 3D mode and so are unlikely to be needed if you are using WWT in freestanding mode:

  • galimg/gal_$N.jpg for N ranging from 0000 to 0255, inclusive
  • milkywaybar.jpg
  • saturnringsshadow.png
  • saturnringsstrip.png