[Qgis-developer] Heatmap renderer: caching possible?

Mathieu Pellerin nirvn.asia at gmail.com
Wed Nov 26 15:46:14 PST 2014


Hmm, handling a cache for the heatmap renderer would probably be quite
challenging. Let's say a temporary raster heatmap is created to ease
panning, you'd have to re do this every time the zoom level is changed. You
could decide to cache as many temporary raster hearmaps as zoom levels
requested by the user during a session, but that'd probably be a memory
nightmare both in terms of nb of zoom levels and resolution of temporary
raster at high level values. All of that cache would also have to be
revoked as soon as the dataset is modified.

In cases where a cache is needed, your probably better off with a formal
raster heatmap.
On 27 Nov 2014 05:49, "Andreas Neumann" <a.neumann at carto.net> wrote:

> Hi,
>
> I tried the new heatmap renderer in QGIS master. It works nicely.
>
> I wonder if we could introduce a caching mechanism in a temporary raster
> layer to speed up zooming and panning? The idea would be to recreate the
> heatmap every time the project is loaded and then cache it while the
> project is open. At least as an option. For small data or smaller search
> radius the live behaviour would still work well, but for larger data sets
> of larger search radius, such a cache raster would speed things up
> significantly, especially in a server scenario.
>
> Would such a cache be technically possible and useful?
>
> Andreas
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