iTwin Reality Data integration

[jjspace]

Description

This PR is building off of #12289 to add an easy function to load Reality Data meshes. Currently we are only supporting 3D Tiles meshes and pointcloud types of Reality Data to keep the initial integration simple. More can be added in the future but they will require different datasources and constructors in CesiumJS and will require a little more thought on how to design the API.

Issue number and link

No issue

Testing plan

• Running the test sandcastle
  • Load the new sandcastle and make sure it loads.
  • Check that the reality mesh in that iTwin loads and shows in the surrounding area.

Author checklist

• I have submitted a Contributor License Agreement
• I have added my name to CONTRIBUTORS.md
• I have updated CHANGES.md with a short summary of my change
• I have added or updated unit tests to ensure consistent code coverage
• I have updated the inline documentation, and included code examples where relevant
• I have performed a self-review of my code

[github-actions]

Thank you for the pull request, @jjspace!

✅ We can confirm we have a CLA on file for you.

[jjspace]

@ggetz I know we discussed it this morning but can you do a quick pass on the API here just to confirm it looks good? then I'll start adding tests.

[ggetz]

Overall API looks good @jjspace! Just a few comments.

[ggetz]

Should this and ITwinPlatform.RealityDataType be marked private for now?

[jjspace]

I shifted this supported list into the only function that uses it. RealityDataType cannot be made private if I want to set it as the type of the param in createTilesetForRealityDataId because of the way types get generated and skipped for private

[jjspace]

@ggetz I've added tests now and I think addressed all your comments above. Should be ready for another look and I think it's close to done if not already there

[ggetz]

This is looking good @jjspace!

I noticed that the reality mesh looks a bit blurry at the default settings. I was getting a comparable visual to other photogrammetry tilesets after setting the max SSE to 4 —

realityMesh.maximumScreenSpaceError = 4;

I'm guessing this may be because the geometric error of the tileset is balanced against the iTwin viewer, what may have different tile selection metrics. Have you seen the same for other Reality Data meshes?

What do you think of passing a default of 4 for all with the type of RealityMesh3DTiles?

[ggetz]

For consistency with createTilesetFromIModelId.

Suggested change

	*
	*
	* @experimental This feature is not final and is subject to change without Cesium's standard deprecation policy.