Positioning 3d-tiles in columbus view

[jsal11]

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

How to position 3d tiles correctly to map tiles? I am using the New York model from sandcastle to show that with Columbus view buildings go to wrong position.

Is there a minimal example where 3d tiles model is positioned correctly on a webmercator projection Columbus view?

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

https://cesiumjs.org/Cesium/Build/Apps/Sandcastle/#c=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

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

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

Newest version, Chrome

[Omar Shehata]

Thanks for reporting this. I think I know why this is happening, but I'm not sure what an easy fix for this would be. I posted some thoughts and details on this in a GitHub issue:

https://github.com/AnalyticalGraphicsInc/cesium/issues/7915

Hopefully we can get some thoughts when others on the team have a chance to give it a look as well.

[jsal11]

We had time to investigate this more and one important condition applies to our use case => Our 3d tilesets use flat projections. So in a way, fixing the new york tileset is not relevant - and it is not even feasible as that tileset is already projected to curved globe.

But good news is that this branch tackles the issue very well:

https://github.com/AnalyticalGraphicsInc/cesium/tree/projections

I wish your team could merge this to master! It is a very promising solution.

An idea: the projections branch has quite many complex changes to the code base. I have been wondering if map projection functionality could be added to SCENE3D mode without so many changes => just make the globe ellipsoid a flat surface and thats all?

[Omar Shehata]

Thanks for digging into this and posting your update. That's good to hear that you've found the projections branch useful! It does attempt to allow for arbitrary 2D projections so I think that's part of what makes it so complex.

Are you able to share a sample of your 3D Tiles with flat projection and how you're using the projections branch to get it to render correctly? If you have a simpler solution to propose in a pull request, I think that will be more likely to get merged in master sooner.