Fix height relative to terrain by david-lively · Pull Request #1797 · CesiumGS/cesium-unreal

david-lively · 2026-02-13T17:06:10Z

Description

When an object is moving, or the camera moves resulting in tileset LOD changes, objects may float above or sink below the terrain. This PR adjusts the actual height as needed to maintain the given distance to the tileset. Properties to control this are added to UCesiumGlobeAnchorComponent.

HeightReference is an enum indicating whether the height of the actor is fixed relative to the tileset or to the ellipsoid. ECesiumHeightReferenceMode::Ellipsoid is identical to the behavior before this PR; no height adjustment will be made.

HeightReferenceTileset specifies an ACesium3DTileset actor, relative to which Height will be interpreted when HeightReference is ECesiumHeightReferenceMode::Tileset. If HeightReferenceTileset is nullptr, no adjustments will be made.

TilesetHeightUpdateInterval how frequently, in TickComponent() calls, for the height to be checked and the actor moved. A value of 1 indicates that this will happen on every call. A value of 2 indicates every second call, and so forth.

clamp-to-ground.mov

Issue number or link

#1472

Author checklist

~~- [ ] I have submitted a Contributor License Agreement (only needed once).~~

I have done a full self-review of my code.
I have updated CHANGES.md with a short summary of my change (for user-facing changes).

~~- [ ] I have added or updated unit tests to ensure consistent code coverage as necessary.~~
~~- [ ] I have updated the documentation as necessary.~~

Testing plan

Open a test scene.
Add a cube to the scene.
Set the cube's Mobility to Movable.
Add a CesiumGlobeAnchor component.
Set the Height Reference value to Tileset.
Set the HeightReferenceTileset value to CesiumWorldTerrain or another ACesium3DTileset actor.
Run the scene.
In the Outliner, select the cube, and modify it's Transform to move it above a hill or other area where the tileset height is different.
Observe that the cube adjusts its height to stay the same distance from the tileset.

It might be easier to set these fields on Dynamic Pawn's CesiumGlobeAnchor, and fly over some terrain while observing that the pawn will remain a fixed height above the tileset.

… that has a GlobeAnchor

…ctionality moved to CesiumGlobeAnchorComponent

j9liu

Thanks @david-lively for the PR! Excited to see this feature come to life.

There are some design choices I would iterate on, so I left some basic feedback for that. I'm happy to do a deeper dive once the design solidifies.

Source/CesiumRuntime/Public/CesiumGlobeAnchorComponent.h

…oid to maintain existing expected behavior.

…ff. Added comments. Extracted heightAboveTileset code to a function. Set initial fixed height when component is registered. Fixed comments.

…dded EditCondition to HeightReference property.

…ce, etc.

…ce is Tileset.

…or to maintain value when changing HeightReference value.

…et when appropriate. Lots of cleanup.

…Reference parameters, reverted change to a test.

j9liu

Thanks @david-lively! This is looking a lot better. There's still a few things that need to be addressed (beyond comment/style cleanup) but I think the implementation seems solid. 😎

j9liu · 2026-02-27T15:32:21Z

Source/CesiumRuntime/Public/CesiumGlobeAnchorComponent.h

      Category = "Cesium",
      Meta = (ReturnDisplayName = "Height"))
-  double GetHeight() const { return this->GetLongitudeLatitudeHeight().Z; }
+  double GetHeight(const bool IgnoreHeightReference = true) const;


See my comment under GetLongitudeLatitudeHeight

Source/CesiumRuntime/Public/CesiumGlobeAnchorComponent.h

Source/CesiumEditor/Private/CesiumGlobeAnchorCustomization.cpp

Source/CesiumEditor/Private/CesiumGlobeAnchorCustomization.h

j9liu · 2026-02-27T16:19:09Z

Source/CesiumRuntime/Public/CesiumGlobeAnchorComponent.h

      Meta = (ReturnDisplayName = "LongitudeLatitudeHeight"))
-  FVector GetLongitudeLatitudeHeight() const;
+  FVector
+  GetLongitudeLatitudeHeight(const bool IgnoreHeightReference = false) const;


Hm, almost wonder if you need a None option and call this parameter HeightReferenceOverride. Or Use Existing Reference or something. Would need to namesmith.

Source/CesiumRuntime/Public/CesiumGlobeAnchorComponent.h

Source/CesiumRuntime/Private/CesiumGlobeAnchorComponent.cpp

…ferenceTileset values. This makes sure the actor maintains its position when changing those values.

Co-authored-by: Janine Liu <32226860+j9liu@users.noreply.github.com>

…-to-terrain' into fix-height-relative-to-terrain

…things.

…or widgets when modifying HeightReference

… readonly status can be correctly updated

j9liu

Thanks @david-lively, this is looking really close!! I confirmed that you were able to fix the few UI bugs I noticed.

I still have one concern re: the OverrideHeightReference boolean in the Blueprints functions, but I don't think it will be a huge lift to address. Happy to talk about alternative solutions too.

Source/CesiumRuntime/Public/CesiumGlobeAnchorComponent.h

…set(). Added ECesiumHeightReference::None to indicate allow clear overriding of the HeightReference value where needed.

j9liu

Looking better @david-lively ! My suggestions are only about comments, that's it.

Source/CesiumRuntime/Public/CesiumGlobeAnchorComponent.h

j9liu · 2026-03-03T20:15:17Z

Source/CesiumRuntime/Public/CesiumGlobeAnchorComponent.h

Suggested change

* and height relative to the specified height reference.

Source/CesiumRuntime/Public/CesiumGlobeAnchorComponent.h

…or dropdown. Comment updates.

david-lively added 5 commits February 12, 2026 15:09

Working, needs cleanup

5be300b

Removed unwanted return

7fdf1c6

Added check for HeightReference enum to avoid messing with everything…

33634da

… that has a GlobeAnchor

Removed ClampToGround component which isn't used in this version. Fun…

674479c

…ctionality moved to CesiumGlobeAnchorComponent

Naming, formatting, cleanup

91e334e

j9liu added this to the March 2026 Release milestone Feb 13, 2026

j9liu self-requested a review February 13, 2026 17:07

Removed debug log message

14b8291

david-lively mentioned this pull request Feb 13, 2026

Easy way to clamp objects to the ground #1472

Open

j9liu linked an issue Feb 13, 2026 that may be closed by this pull request

Easy way to clamp objects to the ground #1472

Open

j9liu requested changes Feb 13, 2026

View reviewed changes

david-lively added 7 commits February 16, 2026 11:31

Renamed enum values. Updated comments. Set default behavior to Ellips…

8bab224

…oid to maintain existing expected behavior.

Fixed fixedHeightAboveHeightReference serialization. Renamed some stu…

362453d

…ff. Added comments. Extracted heightAboveTileset code to a function. Set initial fixed height when component is registered. Fixed comments.

Made queryIntersection method private, updating naming conventions. A…

2e03c1c

…dded EditCondition to HeightReference property.

Formatting

55d0407

Updated CHANGES.md. Clarified comment on TilesetHeightUpdateInterval.

19428d3

Some editor inspector changes for HeightReference and related items

166e620

Added missing UPROPERTY macro to force serialization of HeightReferen…

9a592cd

…ce, etc.

j9liu assigned david-lively Feb 18, 2026

david-lively added 5 commits February 18, 2026 13:19

Mostly working; setting Height doesn't do anything when HeightReferen…

f9ea260

…ce is Tileset.

Works; needs cleanup

6331a51

More cleanup

a76253c

Removed some dead code, simplified a few things.

33d4b6b

Merge branch 'main' into fix-height-relative-to-terrain

1acc9ed

david-lively marked this pull request as ready for review February 18, 2026 21:23

david-lively requested a review from j9liu February 18, 2026 21:23

david-lively added 4 commits February 20, 2026 13:54

Removed redundant coordinate transformations.

d8aa405

Removed redundant coordinate transformations. Fixed Height in inspect…

ea44aa1

…or to maintain value when changing HeightReference value.

Merge branch 'main' into fix-height-relative-to-terrain

ec917b1

Fixed oddity that caused incorrect Height display in inspector

bcf8cf4

Removed weird if(true)

d8394b2

j9liu modified the milestones: March 2026 Release, April 2026 Release Feb 26, 2026

david-lively added 5 commits February 26, 2026 12:44

Corrected height adjustment logic to use height above reference tiles…

03ad609

…et when appropriate. Lots of cleanup.

Cleaned up some stuff, fixed default value and names for IgnoreHeight…

4bdf392

…Reference parameters, reverted change to a test.

Removed #if'd out code.

c19070e

Renamed a private method

808a55e

Added a ClampMin and some cleanup

70115ab

david-lively requested a review from j9liu February 26, 2026 19:41

Formatting

f8b20b8

j9liu requested changes Feb 27, 2026

View reviewed changes

david-lively and others added 13 commits February 27, 2026 15:31

Height is now set correctly when changing HeightReference or HeightRe…

fb8aaff

…ferenceTileset values. This makes sure the actor maintains its position when changing those values.

Update Source/CesiumRuntime/Public/CesiumGlobeAnchorComponent.h

1e96809

Co-authored-by: Janine Liu <32226860+j9liu@users.noreply.github.com>

Update Source/CesiumRuntime/Public/CesiumGlobeAnchorComponent.h

d8d4401

Co-authored-by: Janine Liu <32226860+j9liu@users.noreply.github.com>

Update Source/CesiumRuntime/Public/CesiumGlobeAnchorComponent.h

530d092

Co-authored-by: Janine Liu <32226860+j9liu@users.noreply.github.com>

Addressing PR feedback

3e38a51

Merge remote-tracking branch 'refs/remotes/origin/fix-height-relative…

67ff706

…-to-terrain' into fix-height-relative-to-terrain

PR feedback

2dc2422

Formatting

e1f9d61

Corrected normal calculation used for tileset raycast. Renamed a few …

f2f77e7

…things.

Added InvalidateWidgets meta tag to correctly enable and disable edit…

5b0c365

…or widgets when modifying HeightReference

Added notification when changing HeightReference so that editor field…

31676e1

… readonly status can be correctly updated

Comments, formatting, renaming.

cc5e26b

Incorrect default parameter value.

2f35d02

j9liu reviewed Mar 3, 2026

View reviewed changes

Source/CesiumRuntime/Public/CesiumGlobeAnchorComponent.h Outdated Show resolved Hide resolved

Simplified and refactored _queryLongitudeLatitudeHeightPositionOnTile…

8fcb768

…set(). Added ECesiumHeightReference::None to indicate allow clear overriding of the HeightReference value where needed.

j9liu reviewed Mar 3, 2026

View reviewed changes

david-lively added 3 commits March 3, 2026 16:13

Lots of PR feedback. Hides ECesiumHeightReference::None from the edit…

33c3008

…or dropdown. Comment updates.

Updated a comment.

3004b33

Moved a GetWorld() call inside of #if WITH_EDITOR. Updated change log.

5be709a

Conversation

david-lively commented Feb 13, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Description

Issue number or link

Author checklist

Testing plan

Uh oh!

j9liu left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

j9liu left a comment

Choose a reason for hiding this comment

Uh oh!

j9liu Feb 27, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

j9liu Feb 27, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

j9liu left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

j9liu left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

j9liu Mar 3, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

david-lively commented Feb 13, 2026 •

edited

Loading