User:Tordanik/Proposed features/Open 3D model repository links

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Open 3D model repository links
Status: Draft (under way)
Proposed by: Tordanik
Tagging: key=*
Applies to: Node, Way, Area, Relation
Definition: Link to an externally hosted 3D model
Rendered as: Visible in 3D renderers
Drafted on: 2017-06-19

Using the new key [key]=*, it will be possible to link to a 3D model from the [NAME].

Rationale

[NAME] is a free and open collection of 3D models, under licenses compatible with OSM data. These can be used by 3D renderers to go beyond what's possible Simple 3D Buildings and similar tagging schemes, while still relying on OSM data for the rest of the scene.

Unlike the OSM database, IDs in [NAME] are relatively stable, and lend themselves well to linking. At the time of writing, each ID represents exactly one model, but it may eventually represent a set of models of the same real-world feature (e.g. for different levels of detail).

This proposal only covers basic links. More advanced features may be introduced in the future.

For the most part, this tag is equivalent to building:obm=*, which was in use with OpenBuildingModels (a defunct spiritual predecessor of [NAME]). However, it is not limited to buildings.

Proposed tagging

The suggested tag is key=<id>, where id is the ID of the model in [NAME].

A 3D renderer supporting this tag may then ...

  • obtain the model from [NAME] and place it in that location, and
  • ignore the tagged OSM elements for 3D rendering, to avoid duplication.

Additional tags

At least the following existing keys are taken into account to scale and rotate a generic model:

Other tags and conventions (e.g. deriving a bollard's rotation from the way containing it, ...) should also be taken into account.

Tagable features

The tag applies to all elementsNode nodes, Way ways, Area areas, and Relation relations. When applied to a relation (e.g. a bridge relation or parking relation) or outline (e.g. a building=*) area), features that semantically belong to these "root" elements should also be replaced with the model.

Creating new elements for the sole purpose of linking a model from [NAME] should be avoided wherever possible. Usually, this is a sign that the linked model does not have the intended granularity: Instead of creating a single model containing both a castle and the decorative fountains in front of it, for example, the model should be subdivided into separate models for the building and fountains. These can then be easily linked to existing OSM elements.

Examples

Photo Tagging Interpretation
Coburg-Marktplatz-Brunnen-W.jpg Node node or Area area, tagged Link to an external model for an historic fountain. This id will only appear in the database once, as the fountain is unique.
Bench.jpg 4 Node nodes, each tagged

The direction key defines the facing of the bench, as usual.

Link to a model for the bench design. There will be four instances of the same model.
Rathaus Muenchen - Panorama.jpg Area area, tagged Link to a model of the building. Like the fountain example, but also replaces any building:part=* elements and indoor features of this building.
 Bridge + roads unique example: Tag on the man_made=bridge, roads and other elements on the bridge are implicitly also affected
 Complex unique example

External discussions

  • Diary with posts about the repository's development

Comments

Please comment on the discussion page.