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In your experience, how many point features can be added to an OpenLayers vector layer (new OpenLayers.Layer.Vector("Point Layer")) before it goes unusably slow?
My use case is to display points from a database table. The user can decide which time frame to visualize. Therefore the result can be from very few to potentially 100,000s of points. I'd like to introduce a reasonable limit and warn the user if his query would return more features.
I don't have a definitive answer for you but you I put together a page where you can play around with different numbers of points on an OL map: http://derekswingley.com/lab/olpts/
If the display goes slow because of the too high feature number, it means that the data to display are not suitable for the zoom level. Usually, when the features density goes too high, the display can not be readable anymore (see this example). Even if there was no processing limit and all the display devices were able to display 1000000000000 features in 0.001s on a small screen, the visualisation would remain impossible.
The Töpfer's radix law states that feature density should remain under a constant threshold whatever the zoom level. A way to solve this issue and adapt the data to the visualisation scale is to transform it using generalisation operations like this one or this other one.
I don't think it is not possible to give solid answer for this question. Rendering point/polygons fully depend on browser and hardware (CPU & memory) not with OpenLayers. I had problem with Openlayers and IE6 for one of the Lake (Polygon) rendering. but, it loaded nicely in Firefox. And best option would be monitor the memory and CPU usage with Chrome or some tools would be better.
In OpenLayers 6, there is a WebGL point renderer which should allow you to render 100s of thousands of features, with time based filtering. You May want to check out the latest version of the official workshop at https://openlayers.org/workshop/en/webgl/.
With OpenLayers 2, which I really don’t recommend to use any more, the maximum for acceptable frame rate will be a few hundred features only.
As others, I have no answer regarding that question, but applying a BBox strategy could help you keeping just the needed data since it displays only features located within the given bounding box.
I stumbled on a similar use case, not sure whether it will suit the above mentioned needs but Clustering in OL 5 is what I adopted.
Clustering as the words suggests takes a group of points and merge them togther in a single point e.g. you have 100 points in particular city all the points will be visible as one point from a zoom of let's say 4 but as individual points from a zoom of let's say 10 so what you can do is when the zoom is 4 you can join those points as one, what this does it helps reducing the number of points to be rendered in a particular area.
In other words, let's say you have 10,000 points to be rendered on the map and they are pretty close to each other, so you can make clusters of them and reduce rendering and when the user zooms in you keep breaking the clusters. This will ensure that you have less rendering and better performance.
Satisfying performance. Link to Clustering examples on Openlayers
