Support 3D Tiles feature picking in Viewer

[mramato]

Viewernow has default pick handling forCesium3DTileFeaturedata and will display its properties in the defaultInfoBoxas well as setViewer.selectedEntity` to a transient Entity instance representing the data. While a little clunky, this is identical to how ImageryLayer picking has worked for ages.

[cesium-concierge]

Thanks for the pull request @mramato!

• ✔️ Signed CLA found.
• ❔ Unit tests were not updated.
  • Make sure you've updated tests to reflect your changes, added tests for any new code, and ran the code coverage tool.

Reviewers, don't forget to make sure that:

• Cesium Viewer works.
• Works in 2D/CV.
• Works (or fails gracefully) in IE11.

[mramato]

This area in general isn't super well unit tested and it didn't look like it was easy to test Cesium3DFeature without mocking a bunch of things. Given it's super easy to test with Sandcastle, I didn't worry about it for now.

Here's a link to the OSM demo which now showcases this behavior by default: http://cesium-dev.s3-website-us-east-1.amazonaws.com/cesium/feature-picking-3d/Apps/Sandcastle/index.html?src=Cesium%20OSM%20Buildings.html

[OmarShehata]

This is pretty amazing. Even though I already knew how to do this in my app, this is way more convenient.

One thing I don't get about the code is what happens to the new Entity that's constructed for this - does it need to be explicitly destroyed? Does it just get garbage collected when selectedEntity = undefined ?

[mramato]

One thing I don't get about the code is what happens to the new Entity that's constructed for this - does it need to be explicitly destroyed? Does it just get garbage collected when selectedEntity = undefined ?

No need to explicitly destroy it, it will get garbage collected when the infobox is closed or programmatically unselected.

[mramato]

@OmarShehata I think I addressed your feedback, anything else?

[OmarShehata]

I was considering if we need to update any Sandcastle examples to simplify them, like this one in particular: http://cesium-dev.s3-website-us-east-1.amazonaws.com/cesium/feature-picking-3d/Apps/Sandcastle/index.html?src=3D%20Tiles%20Feature%20Picking.html, but that's doing more than just getting the properties on click (getting it on hover, adding an HTML overlay, highlighting with post processing).

It may be valuable to add a separate code example for extracting the selectedEntity.feature, perhaps something like this but I think we need to change/remove one of the existing ones, because we'll just be showing a lot of different ways to do the same thing and ideally we should show just the easiest way to do it.

[OmarShehata]

I am going to merge this since I am happy with how the feature works, and because the .feature property is documented now, and we can revisit revising the Sandcastle example since we're planning on taking a look at improving how Sandcastle is organized soon.