Model Coordinate System

[VCGP-TIAANJ]

Hi,

I am having issues with my iTwin mode (based in HS2 Snake Grid) being placed geographically not aligned with the Cesium tiling.
My 4D model is working, but it is being placed somewhere in the sky and miles away from the location it should be.

We have resolved this issue earlier, but am looking for a permanent fix to address this issue.

Regards,
T

[AlexandreWalensa]

Hi John,
Thanks for having shared your iTwin.
I have noticed that the "project extents" of your iModel is huge (more than 200 km along the Y axis) compared to the size of the actual model.
This can lead to several issues:

• When loading the iModel, the actual model appears very far away from the camera (more than 100 km in your case), because the GeoReference is set at the center of the project extent box.
• Even after manually fixing the GeoReference position, the model may still appear at an incorrect position because of precision issues due to the large extents.
  So, could you try to adjust the project extents so that it encompasses your model more closely ?

[VCGP-TIAANJ]

Hi Alexandre, We have issues as some of our design files are from external sources and as we are using synchro control, we need to manage version controls by using their latest issued files. As this is the case, I don't have direct control over the model extend. Are there any solutions that can be managed within unreal engine to get the models positioned right ? As I would like to align with the cesium tiles. Would be keen for a quick teams call, if you can run me through any options to position it correctly! Regards, Tiaan Get Outlook for iOS<https://aka.ms/o0ukef>

…

________________________________ From: AlexandreWalensa ***@***.***> Sent: Tuesday, December 10, 2024 13:39 To: iTwin/itwin-unreal-plugin ***@***.***> Cc: JOHN Tiaan-Callum ***@***.***>; Author ***@***.***> Subject: Re: [iTwin/itwin-unreal-plugin] Model Coordinate System (Issue #32) Hi John, Thanks for having shared your iTwin. I have noticed that the "project extents" of your iModel is huge (more than 200 km along the Y axis) compared to the size of the actual model. This can lead to several issues: * When loading the iModel, the actual model appears very far away from the camera (more than 100 km in your case), because the GeoReference is set at the center of the project extent box. * Even after manually fixing the GeoReference position, the model may still appear at an incorrect position because of precision issues due to the large extents. So, could you try to adjust the project extents so that it encompasses your model more closely ? — Reply to this email directly, view it on GitHub<#32 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/BLHRRJPW6IBETAKRX2AXK7L2E3VH5AVCNFSM6AAAAABTIUHQR2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDKMZRGY3DINJWHE>. You are receiving this because you authored the thread.

[AlexandreWalensa]

Hi Tiaan,
The first issue I mentioned (model appearing far away from camera) can be easily fixed in Unreal by shifting the placement of the GeoReferences.
However, for the second the second issue (wrong placement dur to potential precision issue), as far as I know there is no workaround.
It would be very helpful if you could try adjusting the model position and extents in synchro, so that:

• the model is located around the origin in local space (currently the model is around local position |x = 280 km, y = 280 km])
• the extents closely encompasses the model.

This would allow me to quickly see if it is really a precision issue.
In the meantime, I will continue to try to spot a precision issue in the code.