Animation and transitions

• Declare transitions with a duration in milliseconds and bump updateTriggers to restart it.
• Animate TripsLayer by changing only currentTime; keep path and timestamps arrays unchanged.
• Call layer.setProps inside the frame loop instead of constructing a new layer each frame.

var selected = 'BJ-001';

function buildStations(activeId) {
  return new deck.ScatterplotLayer({
    id: 'stations',
    data: stations,
    getPosition: function (d) { return [d.lng, d.lat]; },
    getRadius: function (d) { return d.id === activeId ? 16 : 7; },
    getFillColor: function (d) {
      return d.id === activeId ? [255, 180, 0, 240] : [40, 140, 255, 200];
    },
    transitions: {
      getRadius: 600,
      getFillColor: 600
    },
    updateTriggers: {
      getRadius: activeId,
      getFillColor: activeId
    }
  });
}

var first = buildStations(selected);

var tripData = [
  {
    vendor: 1,
    path: [
      [116.20, 39.80, 0], [116.30, 39.88, 0], [116.41, 39.91, 0],
      [116.52, 39.96, 0], [116.60, 40.02, 0]
    ],
    timestamps: [0, 40, 90, 140, 200]
  },
  {
    vendor: 2,
    path: [
      [116.35, 40.05, 0], [116.38, 39.96, 0], [116.44, 39.90, 0], [116.50, 39.86, 0]
    ],
    timestamps: [0, 60, 120, 190]
  }
];

var tripsLayer = new deck.TripsLayer({
  id: 'trips',
  data: tripData,
  getPath: function (d) { return d.path; },
  getTimestamps: function (d) { return d.timestamps; },
  getColor: function (d) { return d.vendor === 1 ? [255, 180, 0] : [0, 180, 255]; },
  widthMinPixels: 3,
  trailLength: 30,
  currentTime: 0
});

• transitions only interpolate accessor values, not opacity or elevationScale.
• Mixed time units across paths leave some trips permanently invisible.