cesiumgs/cesiumjs-ai-starter-app/czml-time-dynamic-motion

CZML Time-Dynamic Motion

• A moving entity's "position" is sampled, not static:

{ "epoch": "<ISO8601>", "cartographicDegrees": [t0, lon0, lat0, h0, t1, lon1, lat1, h1, ...] } (or "cartesian" samples — [t0, x0, y0, z0, t1, x1, y1, z1, ...], ECEF meters — if the intent specifically asks for a Cartesian/ECEF position rather than longitude/latitude/height). t0 < t1 < ... are seconds since "epoch". Compute the actual sample values yourself from the intent — never leave placeholder values.

• "availability": "<ISO8601 start>/<ISO8601 end>" — bounds when the entity is active; add this

whenever the document packet also carries a "clock" that should bound this entity's lifetime.

• "path": `{ "material": { "solidColor": { "color": { "rgba": [r,g,b,a] } } }, "width": <number>,

"resolution": <seconds>, "leadTime": <seconds>, "trailTime": <seconds>, "materialMode": "WHOLE"|"PORTIONS" } — draws a trail behind a time-dynamic "position". "materialMode" defaults to "WHOLE" (one material for the entire path). Set it to "PORTIONS" when the intent wants the material to change along the path at distinct time intervals; in that case give "material" as an array of interval-scoped materials instead of a single object: "material": [{ "interval": "<ISO8601 start>/<ISO8601 end>", "solidColor": {...} }, { "interval": "<next start>/<next end>", "polylineDash": {...} }]`.

• This same "epoch" + interleaved-timestamp-and-value-samples pattern also applies to any other

time-varying numeric property (e.g. a sampled rotation angle) — not just "position".

Example: a satellite orbit (time-dynamic position + path)

[
  {
    "id": "document",
    "name": "Satellite orbit",
    "version": "1.0",
    "clock": {
      "interval": "2026-01-01T00:00:00Z/2026-01-02T00:00:00Z",
      "currentTime": "2026-01-01T00:00:00Z",
      "multiplier": 60,
      "range": "LOOP_STOP"
    }
  },
  {
    "id": "sat-1",
    "name": "Satellite 1",
    "availability": "2026-01-01T00:00:00Z/2026-01-02T00:00:00Z",
    "position": {
      "epoch": "2026-01-01T00:00:00Z",
      "cartographicDegrees": [0, 0, 0, 500000, 2700, 90, 0, 500000, 5400, 180, 0, 500000]
    },
    "point": { "pixelSize": 8, "color": { "rgba": [255, 255, 0, 255] } },
    "path": {
      "resolution": 120,
      "leadTime": 0,
      "trailTime": 5400,
      "material": { "solidColor": { "color": { "rgba": [255, 255, 0, 128] } } },
      "width": 2
    }
  }
]