Polygon entities are classifying 3D Tiles by default

[lilleyse]

Any polygon created with the entity API is classifying 3D Tiles by default, but it should instead appear underneath.

@bagnell could you take a look at this?

Reported on the forum: https://groups.google.com/forum/#!topic/cesium-dev/leIJUfQ37ro

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

Cesium.CesiumIon.create3DTileset(1458, { accessToken: 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJqdGkiOiIxYmJiNTAxOC1lOTg5LTQzN2EtODg1OC0zMWJjM2IxNGNlYmMiLCJpZCI6NDQsImFzc2V0cyI6WzE0NThdLCJpYXQiOjE0OTkyNjM4MjB9.1WKijRa-ILkmG6utrhDWX6rDgasjD7dZv-G5ZyCmkKg' })
    .then(function(tileset) {
        viewer.scene.primitives.add(tileset);
        viewer.zoomTo(tileset);
    });

viewer.entities.add({
    polygon : {
        hierarchy : new Cesium.PolygonHierarchy(Cesium.Cartesian3.fromRadiansArray([-1.3194369277314022, 0.6988062530900625, -1.3193955980204217, 0.6988091578771254, -1.3193931220959367, 0.698743632490865, -1.3194358224045408, 0.6987471965556998])),
        material : Cesium.Color.RED
    }
});

[bagnell]

I'm not sure if this is the right fix, but you can change GroundPrimitive.classificationType to default to TERRAIN instead of BOTH. The other option would be to add that option to entities.

[lilleyse]

I think adding the option to entities make sense. Having it default to BOTH is probably fine, but the entity API should allow control of it.

Also maybe this is obvious, but why does a polygon default to being a ground primitive?

[hpinkos]

@lilleyse everything defaults to being a ground primitive through the Entity API unless you specify height. This is so it contours to terrain by default.

[hpinkos]

@bagnell @lilleyse We need to fix this before March 1st

[cesium-concierge]

Congratulations on closing the issue! I found these Cesium forum links in the comments above:

https://groups.google.com/forum/#!topic/cesium-dev/leIJUfQ37ro

If this issue affects any of these threads, please post a comment like the following:

The issue at #6195 has just been closed and may resolve your issue. Look for the change in the next stable release of Cesium or get it now in the master branch on GitHub https://github.com/AnalyticalGraphicsInc/cesium.

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