3D Tiles Next CesiumJS Roadmap

[ptrgags]

3D Tiles Next adds several new, experimental capabilities to 3D Tiles. Currently, they take the form of extensions to 3D Tiles 1.0 and glTF 2.0. An overview of these specifications can be found in the 3d-tiles repository. See also the list of resources

This issue tracks the changes to CesiumJS and the implementation status for each.

3D Tiles Next Extensions - Initial Implementation

These features are now available as of CesiumJS 1.87.1

• 3DTILES_implicit_tiling - experimental implementation in Experimental 3D Tiles Next Extensions #9517
  • Implement an Implicit3DTileContent, which transcodes implicit tiles to Cesium3DTile objects when the content loads. This naïve transcoder is similar in function Tileset3DTileContent (external tilesets).
• 3DTILES_multiple_contents - experimental implementation in Experimental 3D Tiles Next Extensions #9517 - However, we found some caveats to the specification, in particular that there is no way to use contents that require mixed ADD/REPLACE refinement. This specification may be revised in the future
  • Implement Multiple3DTileContent
  • Add support for multiple contents in implicit tiling.
• 3DTILES_metadata - experimental implementation in Experimental 3D Tiles Next Extensions #9517
  • Create classes for representing metadata concepts
  • Add tileset, tile, and group metadata to 3D Tiles 1.0 classes
  • Add tile and group metadata support to implicit tiling
  • Add group metadata support to multiple contents
  • Add Cesium3DTileFeature.getPropertyInherited() for CPU styling. Now the styling language will use tileset, tile, and group metadata
• 3DTILES_content_gltf - experimental implementation in Experimental 3D Tiles Next Extensions #9517
• (glTF) EXT_feature_metadata - in progress. This involves significant refactoring of Model.js (see more in the Other Improvements section below)
  • Create classes for representing feature metadata concepts
  • Create a parseFeatureMetadata() function for parsing the EXT_feature_metadata extension
  • Create a parseBatchTable() function to transcode the old batch table into the new feature metadata format. This includes some classes for compatibility with JSON properties and the EXT_batch_table_hierarchy extension.
  • Load feature metadata from a glTF via GltfFeatureMetadataLoader
  • Redesign Cesium3DTileBatchTable to use feature metadata. This will enable using feature metadata for styling.
  • Update Gltf3DTileContent to support feature metadata
• 3DTILES_bounding_volume_S2 - in progress, see PR Adds support for 3DTILES_bounding_volume_S2 #9506
• Custom shaders See roadmap issue basic implementation.

Additional Supporting Extensions

• (glTF) EXT_mesh_gpu_instancing - in progress, requires the Model.js refactor
• (glTF) KHR_mesh_quantization - in progress
• (glTF) EXT_meshopt_compression - future
• (glTF) geolocation extension - future

ModelExperimental Implementation Improvements

General Improvements

• Support noData and required from EXT_mesh_features - Model - support noData and required from EXT_mesh_features #9887
• Add rendering statistics for performance: Add statistics to ModelExperimental, ModelExperimental3DTileContent #9886
• Interpolate per-vertex metadata (see Model: interpolate per-vertex feature IDs #9935)
• Cache shaders and/or pipeline results
• detect quantized vertex colors: GltfLoader isn't correctly detecting quantized vertex colors #9814
• Refactor unit tests, see Improve testing for Model #9813
• Feature texture picking Supporting picking properties from property textures #9852
• consolidate naming conventions between getPropertyIds() and getPropertyNames() - Resolve inconsistency between getPropertyIds and getPropertyNames #9914
• Support feature IDs without a property table Model EXT_mesh_features: handle feature IDs without a property table #9884
• Integration with the 3D Tiles Inspector
• Eye Dome Lighting for individual models Eye dome lighting for Model.fromGltf() #10005

Custom Shaders Improvements

• Allow setting gl_PointSize in a custom shader: Custom Shaders: let the shader control gl_PointSize #9851
• Add cartographic coordinates to custom shaders Custom Shaders: Providing global coordinates to the fragment shader #9735
• Implicit tiling coordinates Custom Shaders: Implicit Tile Coordinates as a built-in uniform? #9736
• Feature IDs in custom shaders Adding feature IDs to custom shaders #9894
• Property textures in custom shaders
• Property tables in Custom Shaders

Pairity with the old Model.js

The intent of ModelExperimental is to someday replace the existing Model.js. Here are the critical steps to get it there:

• Support 3D Tiles 1.0 formats Transcode 3D Tiles 1.0 formats to ModelExperimental #9836
  • b3dm - transcode to ModelExperimental3DTileContent with feature metadata and instancing
  • i3dm
    • Transcode to ModelExperimental3DTileContent with feature metadata and instancing
    • Make sure ModelInstanceCollection will no longer be needed
  • pnts
    • Add support for point cloud attenuation
    • Add support for eye dome lighting
    • Transcode to ModelExperimental3DTileContent with POINTS primitives and metadata
  • cmpt - make sure this is wired up to use ModelExperimental as needed.
  • vctr - transcode to ModelExperimental3DTileContent
  • Support classification models so we can replace ClassificationModel.
• Models that change over time:
  • glTF skinning
  • glTF morph targets
  • glTF animations
• Cesium OSM building support
  • Support CESIUM_primitive_outline glTF extension
  • Support the old batch table hierarchy
• PBR lighting
  • Basic PBR lighting
  • Image-based lighting
• Other existing features
  • custom light color Add lightColor to ModelExperimental #10058
  • Shadows
  • 2D/Columbus View support ModelExperimental - Support rendering in 2D and Columbus View modes #9934
  • Back face culling from constructor
  • clipping planes
  • Clamp-to-ground
• Styling
  • GPU styling Model: GPU Styling #9944 see also GPU Metadata Property Table Packing for 3D Tiles Next #9572
  • Use statistics in the styling language
  • styling point size Cesium3DTileStyle.pointSize in ModelExperimental #10046
  • Use min/max values of metadata properties for better color ramps

Consider Deprecating

• glTF 1.0 support (as it adds considerable complexity)
• KHR_techniques_webgl support (related to glTF 1.0)
• KHR_materials_common support
• Silhouettes as derived commands

[ptrgags]

Updated and reorganized the roadmap. Many of the outstanding tasks have GH issues, I linked them where appropriate.

[lilleyse]

A few more I can think of right now

• Allow dynamic model matrix updates to scene graph. This can be done before animations proper.
• Support AGI_articulations
• Custom shaders (taking some things from styling)
  • Use statistics in the styling language
  • Use min/max values of metadata properties for better color ramps
• Remove all other glTF 1.0 extensions
• Minimum pixel size Add minimumPixelSize to ModelExperimental #10081
• Clean up the Spec/Data/Models folder. All the models should be deleted except those in the Specs/Data/Models/GltfLoader folder which can eventually move into the parent folder.
• Debug wireframe but done correctly - 3D tile wireframe display is tangled #9066

And some comments

• vctr transcode to ModelExperimental3DTileContent may not be in scope for this effort. Let's keep treating it as its own content type Vector3DTileContent. Let's see where the next iteration of vector tiles takes us first.
• ClassificationModel - leverage GltfLoader but otherwise treat as a separate content type since it so heavily uses the vector engine
• I think old batch table hierarchy is already supported...?
• We may still be able to support glTF 1.0 as long as we have a runtime upgrade path that does not involve using KHR_techniques_webgl. This may involve changes in gltf-pipeline and won't work for all assets like the BIM tileset.

[lilleyse]

In addition to basic 2D/Columbus View support...

• Viewing models and tileset correctly in 2D: More accurate rendering of models in 2D #5112

[ptrgags]

One thing to note is new issues about ModelExperimental have their own label of category - ModelExperimental