Problems with CesiumOriginShift

Cesium for Unreal
1

Hello everyone

I’m experimenting with cesium right now and I’ve run into a problem.

I imported a 3rdPersonCharacter from the 3rd person template provided by Unreal, attached the CesiumOriginShift and CeisumGlobeAnchor, and tried to explore the world of Cesium.

However, when using the Change Cesium Georeference mode of CesiumOriginShift to rebase the character to the origin, I discovered that the character was jumping back and forth between two points. After looking a little more closely, I realized that the character should be at (0, 0, 0) after the rebase, but he was teleported to a completely different location.

So I tried to look into the code of the part that teleports the character after the rebase, but it was not easy for me.

I also found a thread with a similar problem to this one, but it was not solved.

Where can I look further here?

I need your help.

How to reproduce

  1. complete the quick start and add datasets from getting start in Cesium for unreal.

  2. import the 3rd person template from Unreal and attach the CesiumOriginShift and CesiumGlobeAnchor components to the 3rd person character. Set the Mode of the CesiumOriginShift to Change Cesium Georeference and the Distance to a reasonable amount (100?).

  3. use 3rd person game mode instead of cesium’s dynamic pawn to explore the world as a 3rd person character.

This is an additional question.

It may not be an issue with Cesium.

In the above reproduction, select the mode of CesiumOriginShift to disable and set the maximum speed of the character (which can be set in the character movement component) to 10000.

You will see a jitter that feels different from the jitter in the rebase.

problem.zip (27.3 MB)

2

I suspect that whatever character/pawn your using is trying to move in Unreal’s coordinate system, rather than Cesium’s world coordinate system. As far as I’m aware Cesium’s dynamic pawn moves by manipulating the CesiumGlobeAnchor component itself, whereas the character/pawn you’re using is trying to change it’s xyz values - I think. To check:

  1. Play the game, click Shift+F1 (to release the mouse if it isn’t already)
  2. Select your character/pawn in the outliner on the right
  3. Select the CesiumGlobeAnchor component and make sure you can see the location values e.g. latitude longitude
  4. Click back in the game window and move around

The location values of the globe anchor should change as you move, if they don’t then I would suggest trying to modify the dynamic pawn to fit your needs as this has movement already set up correctly.

I suspect your last issue is related to

And my issue that you already linked. This jitter can be resolved by using the origin shift, however, the bug is apparently fixed in 5.4 according to

I’m currently in the process of downloading 5.4 and compiling Cesium to be used with 5.4 so we will see if they have indeed fixed it.

3

Thank you for your reply, @SimonLation.

I checked the lattitude and longitude of the CesiumGlobeAnchor as you suggested and it works fine whenever the character moves.

I also looked into character movement.

The character I used receives events from the enhanced input system and calls Add Movement Input.

The dynamic pawn overrides the Move function and calls the same Add Movement Input.

I haven’t noticed any differences between the two except that the character I used is implemented in Blueprint and the Dynamic Pawn is written in C++.

Is there something I’m missing?

4

Learn new information and add it.

The problem didn’t seem to happen when I was in the air, so I added flight to my character to test it out.

As it turned out, it didn’t happen when I was in flight!

However, the moment I landed on the ground after flying and started moving, the flickering started again.

Any suggestions on where to investigate further here would be appreciated.

fly1

5

Seems like the same issue in the second post you linked:

I’m not sure if the third person character uses the spring arm component though? Have you tried the solution there (a modified version of the spring arm I believe.

6

I thought it was similar to the phenomenon in the article.
And I don’t use spring arm’s camera lag feature, but I am using spring arm, so I tried janine’s solution(CesiumOriginShift error - #16 by janine).
But it didn’t work for me and the same phenomenon was repeated.
There seems to be a conflict between UE’s physics engine and Origin shift, but it’s hard to find the cause. :sweat_smile:

7

Hi @KIM_BYOUNGHA,

I’m looking to reproduce this error, but just want to confirm some details.

  • Are you using Cesium World Terrain, or a different dataset?
  • What is the longitude / latitude where you’re seeing this problem?
  • For the 3rd person character, is this the same asset as the one included in Cesium for Unreal Samples? (In the third sample level, 03_CesiumDenver)

It would also help to know if you were able to reproduce this in the Cesium for Unreal Samples directly, so that we can have some common ground to troubleshoot from. Thank you!

8

Hi, @janine

I appreciate your response and will let you know the details.

  • Are you using Cesium World Terrain, or a different dataset?
    • I am using Cesium World Terrain.
  • What is the longitude / latitude where you’re seeing this problem?
    • It happened everywhere outside of sublevels, but the latitude/longitude I tested is (39.742999,-116.990742).
  • For the 3rd person character, is this the same asset as the one included in Cesium for Unreal Samples? (In the third sample level, 03_CesiumDenver)
    • The 3rd person character I used was from the Unreal 5.3 Starter Template example, but I tested by importing the character from Cesium for Unreal Samples and adding a Globe anchor and Origin shift, and the same issue occurred.

CesiumProject - Unreal Editor 2024-05-14 14-16-00

However, I tried to reproduce it by adding a Globe anchor and Origin shift to the character in Cesium for Unreal Samples and it worked.
I don’t know if this is enough, but please let me know if I missed something.

10

Hi @KIM_BYOUNGHA,

Thank you for the detailed information! We’ve seen similar behavior in the past; the “rebounding” usually happens when Enable World Bound Checks is true. Could you make sure that setting is disabled for your own project? You can find it in the World Settings panel.

image
image1002×751 37 KB

Let us know if that fixes it!

11

Hi, @janine
The world’s “Enable World Bounds Checks” is disabled and the character is still rebounding.
I’ll look into it further to see what the issue is. Thanks!
CesiumProject-Unreal-Editor-2024-05-16-09-11-44

12

Hmm, thats a strange one!

We experienced that rebounding with flight, but never just normal walking

Janines Solution of the updated springarm solved the flight issue for us and we didn’t face any more issues with it from there.

We’ll be back working on the project in a week or two, Ill ask my team mate who is the more experienced coder of the two of us, if we find anything that can shed light on it, ill be sure to post screenshots here :slight_smile:

13

Hi, @MQS
Congratulations on the completion of your demo. :tada:
The thread(CesiumOriginShift error - #20 by MQS) and solution was interesting.
It helped me to understand OriginShift better.
Please let me know if there is anything new, or if I missed something. Thanks!

14

Thanks Kim!
Im glad you could learn from our questions, we had to get our mind around it too. But Janine was great in helping us get there and providing some code!

And yes I will keep you in the loop if anything arises :slight_smile:

15

Hi, I found this thread in the UE forum.

The component and function that are currently causing the problem match, and the answers to avoid the problem also seem to match (the forum avoids it by negating collisions, I avoid it with flight mode).
It seems to be UE causing it, but it doesn’t happen in the cesium sample, so there must be something I’m missing.
That’s all for now.

16

Hi everyone. My reply may be coming quite late—the last message in this thread was posted almost 2.5 years ago. However, I think KIM’s last post was actually quite close to the root cause of the issue.

I’m currently using UE 5.8, and I believe the problem is related to the UpdateBasedMovement function in Unreal Engine’s CharacterMovementComponent.

When we place a Third Person Template character with both CesiumGlobeAnchor and CesiumOriginShift components into the scene, the character can be affected by the movement of the Cesium3DTileset. Since the Cesium3DTileset itself is a movable Actor, when the character is standing on it, movement of the tileset can also cause the character’s position to change.

Normally, a character with a CesiumGlobeAnchor should not change its actual geographic position simply because CesiumOriginShift changes the Cesium Georeference. However, I believe this behavior needs to be considered relative to the 3D Tileset as well.

This part is a little difficult to explain precisely, but when Cesium for Unreal shifts the origin, it updates the transforms—including the locations—of both the 3D Tileset and other Actors. The official Cesium World Terrain and Denver sample do not appear to be visually affected, although coordinate changes should still be occurring internally.

The important part is what happens when the character is walking on the ground.

When the 3D Tileset is repositioned as a result of the origin shift, that movement can trigger UpdateBasedMovement. Unreal then treats the tileset as the character’s movement base and applies the base’s movement to the character again. In other words, the character is effectively moved a second time.

I believe this additional movement is what causes the camera jitter.

The workaround I found is to create a custom CharacterMovementComponent in C++, override UpdateBasedMovement, and prevent the default based-movement behavior from taking effect. Then, replace the character’s default CharacterMovementComponent with this custom component.

So far, this approach seems to work correctly, and I haven’t encountered any obvious problems with it.

This is the C++ Code link:

17

Hey @978092768jm,

Thanks for looking into this! Your explanation of UpdateBasedMovement treating the tileset as the character’s movement base and re-applying its motion during the origin shift sounds plausible to me, and points to a UE-side interaction rather than something specific to the sample.

Since you’ve already got it working, would you be open to opening a pull request against cesium-unreal? That’s the best way for the team to review it and potentially add proper handling so others don’t run into the same jitter. The contributor guide covers the steps (it does need a signed CLA before review), and linking this thread would give it context. If a full PR is more than you want to take on, even an issue with the code pasted in would help, since I’m not aware of an existing one tracking this specific interaction.

Cheers!

18

It’s my pleasure, my mehtod in the last post just a Third-party fixes, there are more info in my github GitHub - YaoYingZi/CesiumForUnrealCharacterMovementComponent: 對使用Cesium For Unreal中可能出現的問題的修復 · GitHub , and I am not going to work on PR editing the origin code after a little try, and I think the tutorial may be slightly outdated. When using the latest version of Visual Studio, you may need to install an older version of certain components or toolchains to build the developer’s CMake project successfully. Maybe I am wrong, but the environment setup was so frustrating that it put me off continuing. My programming skills aren’t particularly strong, but I hope my code can still be helpful to your official development team.