Cesium startup scene mode

LibreRally includes a code-first Cesium startup path behind LIBRERALLY_SCENE_MODE=cesium.

Default behavior

  • no environment variables: boots the existing local rally sandbox scene
  • LIBRERALLY_SCENE_MODE=cesium: boots the Stride-native Cesium scene bootstrap
  • LIBRERALLY_CESIUM_STAGE selects the Cesium preset:
    • sample (default): Cesium's public TilesetWithRequestVolume sample
    • melbourne / melbourne-photogrammetry: curated Melbourne photogrammetry
    • google / google-photorealistic / google-photorealistic-3d-tiles: Google Photorealistic 3D Tiles
    • osm / osm-buildings / cesium-osm-buildings: Cesium OSM Buildings
    • file: load a local tileset.json from LIBRERALLY_CESIUM_LOCAL_FILE
    • url: load a contributor-supplied tileset.json URL
    • ion: load a Cesium ion asset

Supported Cesium environment variables

Variable Purpose
LIBRERALLY_SCENE_MODE Set to cesium to boot the Cesium scene path.
LIBRERALLY_CESIUM_STAGE Select sample, melbourne, google, osm, file, url, or ion (aliases supported).
LIBRERALLY_CESIUM_LOCAL_FILE Absolute path to a local tileset.json used by the file preset.
LIBRERALLY_CESIUM_URL Overrides the tileset URL for the url preset.
LIBRERALLY_CESIUM_ION_ASSET_ID Cesium ion asset id for the ion preset.
LIBRERALLY_CESIUM_ION_ACCESS_TOKEN Cesium ion access token for the ion preset.
LIBRERALLY_CESIUM_ORIGIN_LONGITUDE Override the local georeference longitude.
LIBRERALLY_CESIUM_ORIGIN_LATITUDE Override the local georeference latitude.
LIBRERALLY_CESIUM_ORIGIN_HEIGHT Override the local georeference height in meters.
LIBRERALLY_CESIUM_MAX_SCREEN_SPACE_ERROR Override Cesium Native screen-space error budget.
LIBRERALLY_CESIUM_MAX_TILE_LOADS Override maximum simultaneous tile loads.
LIBRERALLY_CESIUM_MAX_CACHED_BYTES Override Cesium Native cache memory budget in bytes.

LIBRERALLY_CESIUM_ORIGIN_LONGITUDE and LIBRERALLY_CESIUM_ORIGIN_LATITUDE use the standard geographic ordering:

  • longitude: east/west, range -180 to 180
  • latitude: north/south, range -90 to 90

For example, central Melbourne is approximately:

$env:LIBRERALLY_CESIUM_ORIGIN_LONGITUDE = "144.9673305"
$env:LIBRERALLY_CESIUM_ORIGIN_LATITUDE = "-37.8175087"

Examples

Run the public sample:

$env:LIBRERALLY_SCENE_MODE = "cesium"
dotnet run --project LibreRally.Windows

Run a custom tileset URL:

$env:LIBRERALLY_SCENE_MODE = "cesium"
$env:LIBRERALLY_CESIUM_STAGE = "url"
$env:LIBRERALLY_CESIUM_URL = "https://example.test/tileset.json"
dotnet run --project LibreRally.Windows

Run a Cesium ion asset:

$env:LIBRERALLY_SCENE_MODE = "cesium"
$env:LIBRERALLY_CESIUM_STAGE = "ion"
$env:LIBRERALLY_CESIUM_ION_ASSET_ID = "1"
$env:LIBRERALLY_CESIUM_ION_ACCESS_TOKEN = "<token>"
dotnet run --project LibreRally.Windows

Cesium camera controls

  • The Cesium startup camera now begins aimed at the local georeference origin.
  • Use W, A, S, D, Q, and E to fly.
  • Hold the right mouse button and move the mouse to look around.

Current scope

This startup path is intended to validate Stride-native Cesium scene assembly, stage selection, and dataset loading. For the current MVP it also enables coarse, camera-local tile collision proxies for nearby streamed content, but it does not yet attempt full rally vehicle-on-globe physics integration.

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