How to create a i3s LOD Tileset from gltf model.

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04-16-2021 09:41 AM
WaqasBakht
New Contributor II

Hello, 

I want to test the I3s tileset using some of our large 3d geo datasets. I am new to Arc and have been struggling to figure out how to create a tileset. 

I have used the Cesium tiling platform, and this accepts gltf files and can create a 3D Tileset with LOD's using that gltf data. But I need to do the same with Arc and I3s. 

If anyone can provide some guidance that would be appreciated!

Thanks, 

Waqas

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7 Replies
Tim_McGinnes
Occasional Contributor III

I would suggest you look at ArcGIS City Engine. It has support for Importing GLTF and Exporting SLPK. Also refer to the Model Export Application Notes, which talks about large models and LODs.

You could ask for a trial version from Esri to see if it will work - it may also be good to contact your Esri distributor directly to ask them if what you want to do is feasible or not.

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WaqasBakht
New Contributor II

Thanks for your response!

Would this work for very large models, say on the scale of Canadian Provinces? 

Thanks Again!

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Tim_McGinnes
Occasional Contributor III

The answer of course is ... maybe! I don't use City Engine, I just remember reading something about GLTF support somewhere. Might be worthwhile posting a question in the ArcGIS City Engine community.

It would help if you could describe your model in a bit more detail, maybe with some screenshots (if it is not confidential). There is a big difference between a full city (or province) wide integrated mesh model vs a model made up of DEM + imagery + BIM + multipatches for example. There may be good reasons to take your original source datasets and bring them into the esri environment via a variety of methods to get the best results.

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WaqasBakht
New Contributor II

Hey Tim, 

Thanks again for your response! 

So I have these large volumetric grids (originally in a vtk format), these models are being triangulated into meshes and converted into gltf. The example here is a voxel grid representing Alberta. This grid is also projected from espg:3978 to WGS84 coordinates during the conversion process.Screenshot 2021-04-18 140412.png

Cesium has a pipeline where they take in a gltf model and can create LOD's and I want to recreate the same thing using Arc's i3s format. I've been trying to use ArcGis pro for this originally but it doesn't seem that simple!

Thanks again for your advice!

- Waqas

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Tim_McGinnes
Occasional Contributor III

Well that's a bit different than what I was expecting. When you say triangulated into meshes, do you mean as a series of stacked solid layers (like a cake) or replicating each individual cell as a 3d object? Is your symbology\colouring fixed or do you expect it to change at run time? Is it just zones, or do you have multiple variables in the grid?

You should also check out Esri's voxel capability in Pro 2.6/2.7. https://pro.arcgis.com/en/pro-app/latest/help/mapping/layer-properties/what-is-a-voxel-layer-.htm. There are a few limitations - only works with NetCDF data at the moment and 3D viewing is only supported in ArcGIS Pro scenes and not yet via web viewers. However additional functionality should be coming in future Pro releases.

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WaqasBakht
New Contributor II

So when converting to gltf, each of those individual layers you see are extracted from the original model and the surface is triangulated. So originally these layers are solid closed volumes, but for the gltf conversion, only the surfaces (of each layer) are extracted during the triangulation process. There is only one property (variable) in this model (rock units or zones). As for the symbology, I don't expect the coloring to be the same but whatever color map used should clearly show each individual layer. 

I had tried CityEngine using a trial license, but it seems the extents of the gltf model are far too large, and  I'm back to trying to figure out Arcgis Pro. 

I did see that there was voxel support in Arc, and my next move was to try and convert my vtk models to NetCDF to view in Arc Pro.

Here is a sample tileset, in the cesium web viewer, showing a lower resolution of that same model converted to Cesium 3d tiles format (which uses gltf as the model payload), using a different color map (this is essentially what I want to see and test in Arc):

 

Screenshot 2021-04-18 180730.png

Anyways, I'll keep at it! Hopefully, I'll get some results soon. Thanks again!

- Waqas

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Andrew--Johnson
Esri Contributor

Hi,

 

Based on the structure of this data I would definitely recommend using a voxel layer. If you can get this data into a NetCDF format then you can add it as a voxel layer in ArcGIS Pro.

https://pro.arcgis.com/en/pro-app/latest/help/mapping/layer-properties/what-is-a-voxel-layer-.htm

thanks,

Andrew

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