Fix reality data not being reprojected correctly when its CRS is different than iModel

[eringram]

There is a bug where when using the reproject parameter of TileTreeReference.createGeometryTreeReference, if the reality data is not in the same CRS than the iModel, the reprojection will put the geometry at the wrong place.

This was because in RealityTileLoader.loadGeometryFromStream, the geometry returned by RealityTileLoader.readGltfAndCreateGeometry is in iModel coordinates, but the reprojection transform is in the reality tree's coordinates.

The fix is to take this difference into account by doing the following:

1. multiply polyface by inverse of tree's iModelTransform to "convert" polyface from iModel CRS->tile tree CRS
2. apply the original reprojection transform xForm
3. multiply by original iModelTransform to convert back from tile tree CRS->iModel CRS

Tested with a couple different iModels with reality data in different CRS. I also added some unit tests for this.

[aruniverse]

@Mergifyio backport release/5.6.x release/5.7.x

[mergify]

backport release/5.6.x release/5.7.x

✅ Backports have been created

Details

• #9074 Fix reality data not being reprojected correctly when its CRS is different than iModel (backport #9059) [release/5.6.x] has been created for branch release/5.6.x but encountered conflicts

Cherry-pick of d122ee6 has failed:

On branch mergify/bp/release/5.6.x/pr-9059
Your branch is up to date with 'origin/release/5.6.x'.

You are currently cherry-picking commit d122ee67a0.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   common/changes/@itwin/core-frontend/eringram-rd-reproject-crs_2026-03-04-23-15.json
	modified:   core/frontend/src/internal/tile/RealityTileLoader.ts
	modified:   core/frontend/src/test/tile/RealityTile.test.ts

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   docs/changehistory/NextVersion.md

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

• #9075 Fix reality data not being reprojected correctly when its CRS is different than iModel (backport #9059) [release/5.7.x] has been created for branch release/5.7.x but encountered conflicts

Cherry-pick of d122ee6 has failed:

On branch mergify/bp/release/5.7.x/pr-9059
Your branch is up to date with 'origin/release/5.7.x'.

You are currently cherry-picking commit d122ee67a0.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   common/changes/@itwin/core-frontend/eringram-rd-reproject-crs_2026-03-04-23-15.json
	modified:   core/frontend/src/internal/tile/RealityTileLoader.ts
	modified:   core/frontend/src/test/tile/RealityTile.test.ts

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   docs/changehistory/NextVersion.md

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[aruniverse]

Nice work! Do we need to run image tests?

[Copilot]

Pull request overview

Fixes incorrect reprojection of reality tile geometry when the reality data’s CRS differs from the iModel’s CRS by converting the reprojection transform from root-tile coordinates into iModel coordinates before transforming collected polyfaces.

Changes:

• Conjugate tile.reprojectionTransform by RealityTileTree.iModelTransform when cloning transformed polyfaces during geometry collection.
• Extend reality tile loader unit tests to cover reprojection when the tree’s iModelTransform is non-identity.
• Add a change file for @itwin/core-frontend.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
core/frontend/src/internal/tile/RealityTileLoader.ts	Applies reprojection in the correct coordinate space by conjugating the root-tile CRS transform into iModel CRS before transforming polyfaces.
core/frontend/src/test/tile/RealityTile.test.ts	Adds tests around reprojection behavior when iModelTransform is non-identity and when it is identity.
common/changes/@itwin/core-frontend/eringram-rd-reproject-crs_2026-03-04-23-15.json	Records the change for the package.

[markschlosseratbentley]

Nice work! Do we need to run image tests?

@eringram I think we should just to be safe.

[eringram]

No image tests differences of note.

The V4 tests had some missing reality data, but I confirmed in the logs it was related to flaky requests for the data and not due to the rendering. The same reality data looked correct in the V1 tests, and since it's reality data and not iModel geometry, the tiles are the same in both versions. (correct me if that doesn't sound right, @markschlosseratbentley ..?)

[markschlosseratbentley]

Does a NextVersion.md entry make sense?

[eringram]

Does a NextVersion.md entry make sense?

Added

[markschlosseratbentley]

Does a NextVersion.md entry make sense?

Added

Thanks. LGTM.

[eringram]

Doing some more testing of this before merging

[mergify]

This pull request is now in conflicts. Could you fix it @eringram? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

[anmolshres98]

@eringram are you planning on getting this merged in today? I am waiting on this to release the next 5.6 patch release. No worries if you are not planning on merging today, just wanted to check :)

[eringram]

@anmolshres98 Hey sorry for the delay, yes planning to merge today. I'll fix the conflicts to do that now.