[OSM-dev] OpenStreetMap Cartographic: A client-side rendered OpenStreetMap Carto

[ndrw6 at redhazel.co.uk]

On 26/05/2020 13:26, Christoph Hormann wrote:
> As Joseph has hinted when it comes to accurate rendering for precise
> mapper feedback without unintentional incentives at the lower zoom
> levels there are other options based on pre-rasterizing the data which
> would still allow using the benefits of client side styling.  I have
> demonstrated that in the past.

Rasterization is a data generalization technique too. Yes, in some cases 
it leaves no artifacts at all but that's not true in a general case and 
almost never true on mobile platforms. It is a viable solution but to 
make it work well the style should not use borders or bake in 
antialiasing (i.e. leave that to the client code).

I am concerned about something else - even with polygon generalization 
in place, the performance is not great. Zooming/panning is rather slow 
on my not so weak PC - the map would be unusable on a mobile device or 
at best it would be draining the battery quickly.

I've been looking into the code and I couldn't find anything related to 
polygon generalization. Where is it done? If it happens automatically in 
the Mapbox GL renderer that's too late - all the cost of preparing 
tiles, transmitting them, processing them in the client has already been 
incurred. Displaying data via WebGL is probably the cheapest part of the 
processing chain.

ndrw