complex shape

1. A concise explanation of the problem you're experiencing.

I have class Pipe. I want to make another class concrete embedded.
That new class should be like (see code bellow) but with some circle inside (empty space along entity).
I don't know how to put circle in shape.

2. A minimal code example. If you've found a bug, this helps us reproduce and repair it.

//from sandcastle
var viewer = new Cesium.Viewer('cesiumContainer');

var greenBox = viewer.entities.add({
    name : 'Green box with beveled corners and outline',
    polylineVolume : {
        positions : Cesium.Cartesian3.fromDegreesArrayHeights([-90.0, 32.0, 0.0,
                                                               -90.0, 36.0, 100000.0,
                                                               -94.0, 36.0, 0.0]),
        shape :[new Cesium.Cartesian2(-50000, -50000),
                new Cesium.Cartesian2(50000, -50000),
                new Cesium.Cartesian2(50000, 50000),
                new Cesium.Cartesian2(-50000, 50000)],
        cornerType : Cesium.CornerType.BEVELED,
        material : Cesium.Color.GREEN.withAlpha(0.5),
        outline : true,
        outlineColor : Cesium.Color.BLACK


3. Context. Why do you need to do this? We might know a better way to accomplish your goal.

To look like pipe is embedded in concrete.

4. The Cesium version you're using, your operating system and browser.

last Chrome, and Cesium 1.46, win 10

If you’re just trying to get a solid pipe look, you can do that with Polyline Volumes. Here’s an example:

Does that help? Or are you trying to make a hollow pipe? Or just put a different material inside?

Something like this:

But with empty space for circle/pipe inside.
Like chimney

Blue object must be circle/pipe, and empty, only borders visible.

To make it a circle, set the shape property to a list of positions describing a circle.

One way to make it appear hollow is to set fill:false. Here is an example of a black pipe outline with a solid blue pipe inside of it:

Alternatively, with Cesium 1.48 you’ll be able to create CoplanarGeometry to create an extruded polygon with holes.

And if none of that is sufficient, you can always create your own geometry type in Cesium. Threejs has a tube geometry whose implementation might be a good guide here.