Interpolating Polygon Positions over Time (using CZML)


Im new to using Cesium and have what is hopefully an easy question. I'm trying to interpolate the positions of a polygon over time in CZML.

There is a similar question on the forum, but the given answer doesn't seem to be working for me. I am assuming this is because the post is quite old and changes have been made since then.

Here is the code I have:

      "id": "thing",
      "polygon": {
          "positions": {
              "references": [
          "material": {
              "solidColor": {
                  "color": {
                      "rgbaf": [0.0, 1.0, 0.0, 0.5]
      "id": "v1",
      "position": {
          "interpolationAlgorithm": "LAGRANGE",
          "interpolationDegrees": 1,
          "epoch": "2012-08-04T16:00:00Z",
          "cartographicDegrees": [0.0, -117.0, 34.9, 2.0,
                                3894.0, -117.1, 34.9, 0.5]

The goal would be to have the vertex represented by 'v1' interpolate over the given time span. When I load this however, I receive a RangeError: invalid array length.

Ive noticed that when the cartographicDegrees of 'v1' is an array of 3 elements (aka as a static geometry) there is no problem. So it seems the time from epoch format is not supported for polygons? Is there perhaps a different approach to accomplishing what I'm trying to do?