Tiled 3D Model - Exported tiles seems to have an offset w.r.t. gltf version

 

Hi,

I have exported the same reconstructed 3d model in both gltf and cesium 3d tiles formats.

The tiled version, however, seems to have an offset w.r.t the gltf one.

The offset is both in altitude and along a ground axis. 

I am using ThreeJS to view both models (for 3d tiles, I load b3dm using some custom code and ThreeJS GLTFLoader).

I dont apply any trasformation (as, for example, tile transforms).

Can you explain why?

Thanks

Andrea

 

 

 

 

 

 

Hi Andrea,

is your model georeferenced? Also, what have you set here:

Have you set Clamp to WGS84 ellipsoid or Unmodified?

Yes, it is georeferenced.

For the altitude parameter, I tried both, but seems to change nothing.

 

Can you please attach your export settings? Which coordinate system are you using?

You have set in GLB export coordinate system as Grid plane, not Projected output

“Project output” does not recenter the whole reconstruction, while the tiled3d model is centered at the origin (not applying tile transforms).

I have tried “shifted project output”, but there seems to be an addional rotation applied to the gltf file.

I have also tried to apply only the rotation part of tile transformation.

For the gltf model I still use “shifted project output”.

Now both models are aligned but still with an offset.

 

 

You wrote, that it is georeferenced, but you have set the Output coordinate system as local. So it is not georeferenced as output. Which of these exported models is on right position? Why the models aren’t the same, when you are exporting one model but just in different formats? Why are you exporting GLB format as Export Model and not Level of Detail as JSON?

Ok, I’ll try to explain more clearly what I am trying to do.

I would like to render the reconstructed 3d model along with the calibrated cameras (as in Reality Capture).

I can easily achieve this by exporting:

  1. the 3d model as glb

  2. the cameras using the Bundler .out format (I am generating cameras frustum geometries on the fly)

I was exporting both using “grid plane” and “local output coordinate system” because I do not  care about georeferencing the whole scene and I want the whole scene recentered at the origin for precision issues.

The problem arises when exporting the model as tiled json.

The tiled version it is no longer aligned with the glb version and thus it is not aligned with the exported cameras.

The tiled version is clearly centered at the origin and relies on the root tile transorm to geolocalize the model.

I am looking for the correct workflow to export both cameras and tiled 3d model aligned correctly both recentered.

 

 

 

 

 

 

 

 

 

Hi, is it possible to share your project with us?

Hi, sorry for the very late reply.

I have solved by using local reference system in both project and output systems.

If you are still interested I will setup a minimal project to reproduce the error.

Anyway, it would be very useful to have more control on the output reference system for 3d tiles like what happens for standard mesh export. 

 

Best,

 

 

Hi Andrea, good to hear that you were able to solve it. It seems that it was caused by different coordinate systems. Thank you for your ideas.