Height affecting ground primitive polygon rendering

[r-edwards]

What happened?

I'm currently creating a GroundPolylinePrimitive using GroundPolylineGeometry, as well as a GroundPrimitive that uses a PolygonGeometry to "fill" the polyline. I'm giving both the GroundPolylineGeometry and GroundPrimitive the same positions, however the polygon shape does not seem to match the polyline. See the attached screenshot:

I've previously worked from a fork of cesium at version 1.99.0 in which the positions of the polygon do correctly "fill" the polyline. For example here is a screenshot running locally of the same scenario as the linked sandbox but with cesium version 1.99:

Here's the code for this example running at cesium v1.99.0:

var Cesium = require('cesium/Cesium');
var viewer = new Cesium.Viewer('cesiumContainer');

const cartographics = [
    {
      "longitude": -1.8402495415863134,
      "latitude": 0.7033934337801941,
      "height": 2177.974000000284
    },
    {
      "longitude": -1.8402506824369915,
      "latitude": 0.7033901872332414,
      "height": 2177.9740000000156
    },
    {
      "longitude": -1.840249836934684,
      "latitude": 0.703388112597783,
      "height": 2177.9739999988838
    },
    {
      "longitude": -1.8402478059109948,
      "latitude": 0.7033903665805613,
      "height": 2177.9739999987028
    },
    {
      "longitude": -1.840246112964614,
      "latitude": 0.7033920799454119,
      "height": 2177.9739999996555
    },
    {
      "longitude": -1.8402467855800173,
      "latitude": 0.7033933442953648,
      "height": 2177.9740000006414
    },
    {
      "longitude": -1.8402495415863134,
      "latitude": 0.7033934337801941,
      "height": 2177.974000000284
    }
  ];

const { WGS84 } = Cesium.Ellipsoid;

const positions = WGS84.cartographicArrayToCartesianArray(cartographics);

const c = Cesium.Color.fromCssColorString('#ffe566');

const polygonGeometryInstance = new Cesium.GeometryInstance({
    geometry: new Cesium.PolygonGeometry({
        polygonHierarchy: {
            positions,
        },
    }),    
    attributes: {
        color: new Cesium.ColorGeometryInstanceAttribute(
            c.red,
            c.green,
            c.blue,
        ),
    },
});

const polygonPrimitive = new Cesium.GroundPrimitive({
    geometryInstances: polygonGeometryInstance,
    appearance: new Cesium.PerInstanceColorAppearance({
        closed: true,
        translucent: true,
    }),
});

const lineGeometryInstance = new Cesium.GeometryInstance({
    geometry: new Cesium.GroundPolylineGeometry({
        positions,
        loop: false,
        width: 3.0,
    }),
});

const linePrimitive = new Cesium.GroundPolylinePrimitive({
    geometryInstances: [lineGeometryInstance],
    appearance: new Cesium.PolylineMaterialAppearance({
        material: Cesium.Material.fromType('Color', {
            color: c,
        }),
    }),
});

viewer.scene.primitives.add(polygonPrimitive);
viewer.scene.primitives.add(linePrimitive);

viewer.scene.camera.flyTo({destination: positions[0]});

Interestingly when using cartographics with zeroed height they seem to match up (note this sandbox).

How is height intended to affect a ground primitive? Is this a regression, or expected behaviour?

Reproduction steps

1. Create a ground primitive using polygon geometry, and a ground polyline primitive using ground polyline geometry using the same positions in example sandbox/code snippet
2. Note that they don't quite match up

...

Sandcastle example

https://sandcastle.cesium.com/#c=tVZbb5tIFP4ryPsQLLljYLgMrhNtZK26lbpqpVS7D3EeJjC2Rx0zaGZI5Eb+73vAYANx7FhqeYE55zuH71whkZk21hNnz0xZ11bGnq0Z07xYo38rmT0fJNV5JjNDecbUfDD8OM/mWVJZJlQZuVQ0X/FEg4P7eWbB9bK7WdZ8IGS25KZI2XwwsT64iPiO58eB7wYkxC72Ry0oNXukgyIH4xj7GEfEcWPfbQFXjC9XpoR5bhShOPKd6vKIvwNtR+/iETgh8XwcxrEbnObhuCTyMPZ8138HD8cNwouI+DEBFtgPyel8EOK6XhBHEcGnaOC4vAghmFxGA1IdxK4Txz45kw8chgGAQ/c9RCKozGVEQogzDuF2pj88JwKy0E1ufJ5HHAZBcCGPiAQQp+NG+EyjYt/34gCHncy91SAh9NGFDfK7J6a8PbQm+8X679Md8a0tTHW9Ev4Sguda8rQFy6XmhsMjwCoD1F4Jt0rRzXc5AxG4oFl1tjtL47BNpGBIyKW9d9lZNAcaMymkQgsl1zOtq8OdUTxb2ld/LBYsCMOrYYeg2Cxl9onJNTNq8xlkNEtYd9n1tXZdjmUtn7TB37oe7X3prOZlf3OmqEpWYNdS7gB1bKODvGmB7XBUFas6UAMxPRaQto6PpAy3w6ZKQJ//bWNtd1+fIMXSUV+2VIxlr6SPomAt4XB0aNjtkQR/U3wNoT31M6tkkaV7ZT+xDWGI8o1C1a+lec6oKgXdWjDVAKtE3O5h7bIkQmqWTiyjOiEZAGpRJCwzHd122I9RwJfvF3ZQnRQIuO2420iv+0RImU+sBRW6HcQzT81qYmHknGR/ujw1k/eU6f5YLh7OVKn2/w81THEqjldpXWsnjVkDr2b9+yZn9lVV5KtRf6zqsUjaUzU8ko/djw7SUHKG8iZajWia2v0+Li1O4TsJe73FOqYJXcNGOMJhp0ALAVvSfkmZNjyjZeEnhxa4dx5q+oPRYKrNRrCbJs4/+TqXyliFEjZCY8PWOXwTmB4/FskPZlCiqy1aQqfjtuk05U8WT6+P/N/BuFCtQbMohLjjP+HrcjMdA/6VqZA0hcX79YkpQTclbOXefNkJEULTMRyPWxopxSNVPc//Aw

Environment

Browser: Chrome 121.0.6167.160
CesiumJS Version: 1.115
Operating System: Mac OS 13.5

[ggetz]

Hi @r-edwards, thanks for reporting this issue!

The 1.110 release included some significant changes to how we handle polygon rendering. This does appear to be a regression.

[n0rdlicht]

@r-edwards thanks for reporting, I can second the behaviour change as we are seeing the same regression when we tested upgrading from 1.105 to 1.113 recently. In our testing it seems at least until 1.116 polygons behave as reported.

@ggetz is there an update on if this will be addressed or a possible workaround in the meantime? Many thanks in advance.