[Example] Google Photorealistic 3D Tiles

[jailln]

Add an example displaying Google Photorealistic 3D Tiles:

https://cloud.google.com/blog/products/maps-platform/create-immersive-3d-map-experiences-photorealistic-3d-tiles?hl=en
https://developers.google.com/maps/documentation/tile/create-renderer?hl=en

[AnthonyGlt]

I've tried to display these tiles in iTowns, I had to do some workaround but the result is nice and probably worth the integration:

We need to;

• Implement a new C3DTilesSource (like what was done with C3DTilesIonSource). It's necessary to request the Google tiles by giving the API key and sessionId for each call.
• Implement a GLTFParser and a C3DTGLTFExtension to handle 3DTILES_content_gltf
• Don't forget to enableDracoLoader

I did a quick test of the implementation but my work is not good enough for a PR, the tiles are not correclty loaded, some faulty behaviors. But I believe that it could be implementable without too much effort.
Faulty loading of tiles:

[jailln]

Cool thanks! Regarding "faulty loading of tiles", it looks like some tiles may be under the ground, we can try to offset each tile a little bit to verify if it's not the cause of the wrong display

[AnthonyGlt]

You were right, by hiding the globe layer, we can see that the tiles are loaded . Still unstable though.

Screencast.from.31-05-2023.11.47.57.mp4

[jailln]

that may come from the bounding boxes that are considered axis aligned while they should not. I'm currently working on that

[alexLuky]

@jailln
perhaps fixing this issue you'll find the reason why Cesium renders sphere boxes more stable than itowns does.
Previously it was mentioned in these issues: 1, 2, 3

[jailln]

Useful insights about google tiles querying: CesiumGS/3d-tiles#746