Pier/landcover sorting

[mrwojo]

Piers render over landcover. For natural=beach, this is generally good. For some other tags, such as tourism=attraction, leisure=park, and amenity=parking, this is often not good. layer=* can't fix this problem because piers and landcovers are rendered separately.

Brighton Pier and Wildwood piers have attractions that should be pink areas on the pier.

Santa Cruz Wharf: A large part of it is a parking lot that's invisible except for a few bits that stick out from underneath the pier area.

Now it get's a little trickier:

Santa Monica Pier should probably continue rendering over (or distinct from) the park underneath. But how about this pier park? It should be green. Mappers may need to use layer=* to differentiate these.

And importantly the render order is (from back to front):

1. landcover
2. water (non-ocean)
3. water-features (including piers)

With all that said we'd still need to have piers render over water and water over landcover.

Any ideas on how to break the circle or otherwise improve the existing the behavior?

[gravitystorm]

It's something that came up a few months ago, but I haven't thrashed through it fully in my own mind. I suspect there's something to do with physical vs administrative in the landcover - e.g. "sand" is representing a feature on the ground, whereas "theme park" is more of an overlay (and currently implemented as such). However, I don't want to end up giving sand and buildings a pink tinge if they are in a tourist attraction, nor make everything a bit green when in a park.

However, maybe that's making things too complex - maybe there's a simpler solution for the case of piers.

[matthijsmelissen]

See also https://trac.openstreetmap.org/ticket/3517

[matthijsmelissen]

We have no way to determine whether a parking, for instance, is on top of or under the pier, so I think the only way to definitely fix this is looking at the layer tag. That would require answering #53 with 'yes', and including piers in the landcover layer.

In general, including pier in the size-based sorting of landcover might already solve most of the issues we currently have.

Opinions?

[jeisenbe]

Now that we have switched to water polygons, and landcover is rendered under water-areas and piers are rendered above water-areas, I don't think there is a way to solve this issue. We also removed landcover sorting by layer and #53 was closed by #2823

So we can close this issue as wontfix?

[jeisenbe]

Actually there is one possible solution, but it requires more comp-op changes:

0. Implement Separately adjusting rendering over water and over land #3854, which would mean that water areas would be "cut out" of the landcover using dst-out
1. Change order to first "cut out" oceans and other water areas prior to rendering landcover.
2. Next render pier areas in land-color (or any other color),
3. Then render landcover with comp-op: src-atop, which means that landcover would only be rendered on top of land and piers
4. After that, water areas would be rendered behind as described in Separately adjusting rendering over water and over land #3854