Do not render link roads until z12

[matthijsmelissen]

This improves rendering on mid zoom levels by smoothing up the highways.

Before:

After:

This becomes especially important after implementing something like #2194 (comment):

Before:

After:

[imagico]

I suppose you mean z<12.

Could this result in gaps in cases like here:

http://www.openstreetmap.org/#map=15/42.1637/12.6129

[matthijsmelissen]

I suppose you mean z<12.

Yep.

Could this result in gaps in cases like here:

Likely yes. Unfortunately Luxembourg doesn't seem to have a case like this.

[nebulon42]

It reduces clutter which is great but on the other hand it leads to gaps at junctions and there are also some longer link passages that could have some relevance on < z12.

Compare https://www.openstreetmap.org/#map=11/48.0510/16.4991 of Vienna's south east with

(I have not checked if the tagging is accurate.)

So I'm leaning a bit to the negative side due to the side effects, but otherwise it would be a good improvement.

[HolgerJeromin]

Even in Luxembourg we have a problem. Last image from math.

Rendering links like the connecting highway (yellow?) is probably not a good idea, too.

[matthijsmelissen]

Thanks for the examples!

[pnorman]

Lately I've gone for starting rendering of links at z10 in my projects. I've found if I increase that it leads too too many problems of gaps.

[matthijsmelissen]

Google Maps has the same problem, by the way (see bottom):

[imagico]

We probably need to consider

1. what our expectations of quality are here.
2. what side effects rendering artefacts will have regarding mapping practice. I suppose if we have visible gaps at larger highway crossings with long links people will be tempted to at least partly tag the links as normal highways.

You might also consider some fancy logic only removing topologically redundant links but that is probably too expensive for us.

[HolgerJeromin]

Rendering links like the connecting highway (yellow?) is probably not a good idea, too.

After thinking about it more this could probably work. Calculating the connecting road class is probably not doable, but render all motorway links with a primary color could be nice.

[pnorman]

Perhaps instead of z12 (proposed) or z9 (current) we could go with something between them?

[pnorman]

As this has cartography changes, this PR is currently held up by the feature freeze until 4.0.0 has been released.

[matthijsmelissen]

Thanks for all comments. I have changed the PR to only drop link roads up to z11 (rather than z12). Merged.

[nebulon42]

Hm, I have the impression that recently it doesn't matter any more so much if others have concerns about changes. They get merged anyway. I think that decreases quality.

[nebulon42]

Also: Didn't we have the requirement that there has to be at least one approving review?

[matthijsmelissen]

You're right, I reverted this merge. As it is not possible to re-open a PR, I created a new PR here: #2758 Could some of you please review it?

[kocio-pl]

I have warned about problem with reviews lately. Lack of discussion seems to be a bigger factor regarding quality than making informed decision.

[matthijsmelissen]

Sorry, I'm not sure if I understand what you mean with you last commebt?

[kocio-pl]

It was response to both @nebulon42 comments.