Use an external library for 3D Tiles

[jailln]

Don't hesistate to complete this post with more information such as analysis criteria or datasets.

We have been thinking about using an external library to handle 3D Tiles to reduce maintenance and bugs. We have identified three possible options:

• 3DTilesRendererJS: parses and renders 3D Tiles, based on threejs
• loaders.gl: contains everything to parse, and handle 3D tiles for rendering (culling for instance)
• three-loader-3dtiles: Uses loaders.gl to load 3D tiles and displays them with threejs

They should be analyzed against itowns implementation with the following criteria in mind:

• License
• Community, activity, etc.
• Possibility to contribute
• Dependencies / bundle size
• 3D Tiles support (1.0, 1.1 and also previous versions official or unofficial in which there are still tilesets available) and GLTF support (1.0 and 2.0)
• Performance

Given the wide variety of 3D Tiles datasets available and of the variety of possible representations (meshes with or without textures, point clouds, gltfs, instanced meshes, multiple possible bounding volumes, draco and ktx2 compression, etc., etc.), we need to test against multiple datasets. Here are some datasets that I have gathered (some of them are private and I cannot share them but I can run tests on them and post the results):

3D Tiles 1.0

b3dm without textures:

• https://github.com/CesiumGS/3d-tiles-samples/tree/main/1.0/TilesetWithDiscreteLOD: A dragon with multiple LOD in the USA, EPSG:4978
• https://github.com/CesiumGS/3d-tiles-samples/tree/main/1.0/TilesetWithRequestVolume: Tileset with request volume, EPSG:4978
• https://saturnus.geodan.nl/maquette_nl_compressed/data/amsterdam_test/tileset.json: Amsterdam buildings, EPSG:3857
• Bordeaux agglomeration (Private), EPS:4978, draco compression, 226Mo

b3dm with textures:

• https://github.com/iTowns/iTowns2-sample-data/tree/master/3DTiles/lyon_1_3946_textured_draco: Lyon 1er borrough, EPSG:3946
• https://github.com/iTowns/iTowns2-sample-data/tree/master/3DTiles/lyon_1_4978: Lyon 1er borrough, EPSG:4978, draco compression
• Lille (Private), EPSG:4978, 817Go, from photogrammetry, with LOD
• Bordeaux (Private), EPSG:4978, ktx2 compression

pnts

• https://github.com/iTowns/iTowns2-sample-data/tree/master/3DTiles/lidar-hd-gorges-saint-chely-tarn: Gorges Saint Chely du tarn (from IGN LIDAR HD), EPSG:4978
• https://github.com/iTowns/iTowns2-sample-data/tree/master/pointclouds/pnts-sete-2021-0756_6256: Sete (from IGN LIDAR HD), EPSG:4978, with classification
• Lyon agglomeration: can be created with py3dtiles from this dataset
• Luxembourg subset (Private), EPSG:4978

i3dm:

• https://github.com/CesiumGS/3d-tiles-samples/tree/main/1.0/TilesetWithTreeBillboards: instanciated trees, EPSG:4978
• Lyon agglomeration trees (Private), EPSG:4978

3D tiles 1.1

• https://github.com/CesiumGS/3d-tiles-samples/tree/main/1.1: Cesium official examples of 3D Tile 1.1 datasets

Note that the private datasets have been generated with multiple open source tools such as py3dtiles, py3dtilers, pg2b3dm, i3dm-creator, etc. and have been compressed with draco and ktx2 so it allows to test datasets produced from diverse tools and with diverse representations.

Other possible sources:

• TU Delft 3D datasets list: https://3d.bk.tudelft.nl/opendata/opencities/
• Univ Singapour list: https://ual.sg/project/ogbd/

For benchmarking, I identified three common usecases that can be tested:

• Fixed scene loading: launch the page with a fixed camera position centered on the dataset (optionnally at multiple zoom levels)
• 3D navigation: simulates user navigation in the 3D scene with predefined camera positions and camera animation with CameraUtils functions to animate camera (don't forget to pan, rotate, etc. like a real user would)
• Strong zoom: Start at a fixed camera position centered on the dataset (wait or not until data is loaded) and zoom a lot and quickly on the dataset

Some indicators that can be analyzed are:

• FPS
• GPU memory
• Loading and rendering time
• Visual impression (subjective but does it seems smooth, etc.)

Post your pocs, benchmarks, etc. in comments

[jailln]

After a first analysis and first tests, we are more oriented on using loaders.gl (and maybe three-loader-3dtiles or some of it?) because loaders.gl has a big community and seems more sustainable (and we already use its las module).

@gchoqueux I think you implemented an integration of itowns with loaders.gl, can you post your branch and your first tests results please?