is there an equivalent of extrude of kml in czml

CesiumJS
1

Hello ,

I have found cesium very amusing product so far, but got stuck at extrude:
in kml of GE we have altitudeModes like relativeToGround, relativeToSeaFloor,
clampedToGround, clampedToSeaFloor and absolute, as far as i have understood cesium do not provide the above altitude modes. if so please let me know the default altitude mode provided by cesium.

also extrude is associated with the altitudeModes in KML which is boolean true(1) or false(0), does cesium API support extrude functionality for polylines, polygon, placemark , if so please let me know how to go about it in CZML.

sample kml for extrude is as given below:
<LineString>
    <extrude>1</extrude>
    <altitudeMode>relativeToGround</altitudeMode>
    <coordinates>
      -121.835,48.754,700
     ............
      -121.773,48.747,700
    </coordinates>
  </LineString>

thanks,
neel