search

mapbox / vector-tile-spec

Mapbox Vector Tile specification
https://www.mapbox.com/vector-tiles/specification/
Other
890 stars 209 forks source link

Simplified/unified extra dimensions and per-node attributes #127

Closed e-n-f closed 5 years ago

flippmoke commented 5 years ago

Some issues with this design currently:

We lose the concept of global_offset vs local_offset which I feel is value-able especially. Additionally all this information is repeated for each Feature when it should likely be the same for each layer.

Next I feel that we should still have another field that is specifically for elevation. We could add this directly as the 3rd dimension in our encoding.

optional Dimension elevation = 999;

As we discussed I still feel it is important for a Layer's features to be all 3d or 2d.

e-n-f commented 5 years ago

Good point about giving elevation its own message so that it has explicit semantics.

If you still want the offset and scale to be part of the layer, I don't really understand how this differs from the previous idea, except for wrapping each dimension in a container object.

I do not think it is enforceable to require that every feature in the same layer have the same number of dimensions. I am reluctant enough to require this of every node in the same feature. GeoJSON does not require that features have consistent numbers of dimensions and shapefile allows NaN in the M dimension so if we do not allow nulls we will find legitimate user data to be unrepresentable.