The map is lagged when the polyline consists of a large number of points

[Vafin84]

Hi guys! I am experiencing performance problems when a polyline consists of a large number of points (for example, more than 7000 points), the map starts lagging and the FPS drops. Is there a way to increase productivity? For example, it would be possible to render only what is visible on the screen.

[JaffaKetchup]

Hi there,
Unfortunately this is a well known issue (although previously known for markers, the same issues apply).
At the moment, you can try enabling: polylineCulling: true in PolygonLayerOptions but it is not guaranteed to fix your issue. Hope it works!

[Vafin84]

Hi there, Unfortunately this is a well known issue (although previously known for markers, the same issues apply). At the moment, you can try enabling: polylineCulling: true in PolygonLayerOptions but it is not guaranteed to fix your issue. Hope it works!

Thanks for the answer. I've tried toggling polylineCulling on / off, but unfortunately it doesn't help much. I see the following steps in solving this problem:

1. Render only the part of the polyline that is visible on the screen.
2. Remove some points from the list of points of the polyline when zooming out

[ibrierley]

I can't remember how the polyline culling works just off the top of my head, but if you have one polyline with 7000 points, that's quite a lot....maybe it would be more optimal to have the poly broken into multiple lines so it can cull differently (this would only working depending how the cull code works). You could also look at line simplifcation at certain zooms or something (I think there's some line simplification code floating about somewhere).

[Vafin84]

I can't remember how the polyline culling works just off the top of my head, but if you have one polyline with 7000 points, that's quite a lot....maybe it would be more optimal to have the poly broken into multiple lines so it can cull differently (this would only working depending how the cull code works). You could also look at line simplifcation at certain zooms or something (I think there's some line simplification code floating about somewhere).

Thank you. I will try to break the polyline into parts to test this.

[mziadd]

@Vafin84 Hi, do you come up with a solution, i have the same proplem.

[JaffaKetchup]

#958 may also help here?

[mziadd]

@JaffaKetchup i mean the solution about breaking polyline into parts.

[JaffaKetchup]

@mohammedX6 Not sure, but if search Google for chunked list in dart, you'll probably get an algorithm that splits a list into smaller parts through 2D lists. You can then use the .map method to map to a polyline.

[ibrierley]

I'd be interested if someone has a test data set and widget that's causing problems. Nothing like real world examples to look at.

[Vafin84]

@Vafin84 Hi, do you come up with a solution, i have the same proplem.
Yes, I found a solution, but I don't know how good it is. I create a polyline only from those points that enter the boundaries of the phone screen. I get the borders of the screen through the map controller.

[mziadd]

@Vafin84 Can you share the code?

[Vafin84]

@Vafin84 Can you share the code?

Unfortunately, I do not have the right to distribute the code, because I signed an agreement with my employer.

[Vafin84]

@Vafin84 Can you share the code?

Just create a condition for a list of all polyline points. If the point is included in the borders of the screen, then we add it to a separate list from which a polyline is formed in the future. Every time the borders of the screen change, it is necessary to recalculate the polyline.

[ibrierley]

I assume that would be a relatively straightforward map over every point and previous, see if they are within bounds eg map.pixelBounds.containsPartialBounds(x,y) ?, if so add to the new polyline list ? or is it more complex than that ?

Edit: Sorry, beat me to it.

[Vafin84]

I assume that would be a relatively straightforward map over every point and previous, see if they are within bounds eg map.pixelBounds.containsPartialBounds(x,y) ?, if so add to the new polyline list ? or is it more complex than that ?

Edit: Sorry, beat me to it.

Yes, it is exactly as you said. In addition, I made an additional optimization as follows. It is necessary to recalculate the polyline only after the animation or actions on the map are finished (for example, changing the zoom or moving around the map). Additionally, I recommend simplifying the list of points depending on the zoom, so when the zoom is reduced, good detail is not needed.