Use Mapnik simplify algorithm instead of a dedicated file

[yohanboniface]

It's a bit (not that much) slower, but given it's all pregenerated tiles, it's harmless. And it makes the workflow much simpler.

@kent1D can you have a check, given it's a sensible topic? :)

I've already deployed on the preprod site so you can check it with other data (only in Africa):

https://carte-mae.enix.org/#4/-3.25/25.66

[kent1D]

What I see is that it a bit less precise of the older way to do that

And it leaves some holes.

Is there a big performance issue playing with line-simplify ?

[yohanboniface]

And it leaves some holes.

Oops. Can you point me to one? :) It may just be a matter of finding the right tolerance.

Is there a big performance issue playing with line-simplify

Nope, not big.

[kent1D]

Where it's quite visible is where there is not concrete other datas because no sub admin level boundaries.

Some polygons appear.

At zoom 4 the most, some examples :

• around Bhutan
• North of Iraq
• between Tadjikistan and Afghanistan
• around Switzerland

[kent1D]

Or maybe there is an option to clip them?

[yohanboniface]

Seems I'm totally missing something here :( May be related to screen resolution or something.

Here is what I see (feint: after is on the left, before in on the right):

I detect no hole nor lack of precision :s

[kent1D]

hmmm quite strange, here is what I see on carte-mae.enix

Look around Belgium / Netherland, Moldavia / Romania

[kent1D]

Ok yours is @2x and mine is @1x

I have two screens on my computer, one retina and the other not, and effectively it's not the same ;)

[kent1D]

I will try your branch this afternoon and try to play with the simplification option and tell you

[yohanboniface]

Ok yours is @2x and mine is @1x

Bah, makes sense, "my" images are twice bigger, so simplification is twice lower, so I've adjusted a bit high for the normal images.

I will try your branch this afternoon and try to play with the simplification option and tell you

Cool, thanks. I'll make a try with half the simplification in the meantime :)

[yohanboniface]

I'll make a try with half the simplification in the meantime

Sounds better for normal tiles with 5, and of course it's less simplified with the retina one, but it's more acceptable that way. One option may be to use pixel_width/height to adapt the tolerance. Given the pixel_height changes either with zoom, map scale and latitude, it's certainly too much of an alchemy to play with it. AFAIK, pixel_width should only change with zoom and scale (not with latitude), so it may worth a try.

But at the end I'm not even sure if it's a bug or a feature that the line-simplify algorithm does not seems to take into account the map scale. @springmeyer any hint from the top of your head on this?

[kent1D]

Oups? j'ai fermé, désolé... je ne sais pas comment, il ne faut pas me donner trop de droits :D

C'est beaucoup mieux sur la version actuelle

[springmeyer]

@springmeyer any hint from the top of your head on this?

No, not looked at that code for a long time now.