[mapserver-dev] RFC97: Dynamically Creating High Zoom-Level Tiles
woodbri at swoodbridge.com
Tue Apr 16 07:51:31 PDT 2013
+1 great idea.
Duh! Told you I hadn't had enough coffee, got up and down flipped in my
On 4/16/2013 9:43 AM, thomas bonfort wrote:
> if max is 15, you would only resample for levels 16, 17 and up, i.e.
> always from a single tile using the common power-of-two grids (g, wgs84,
> ...) or at the worst from 4 tiles for the other ones.
> so z <= max-cached-level : usual behavior
> z > max-cached-level : upscale from tiles where z=max-cached-level
> clearer ?
> On 16 April 2013 15:36, Stephen Woodbridge <woodbri at swoodbridge.com
> <mailto:woodbri at swoodbridge.com>> wrote:
> On 4/16/2013 2:43 AM, thomas bonfort wrote:
> Please find RFC97:
> A bit short for an RFC, but a bit too long for just a ticket...
> This RFC
> basically allows serving tiles from high zoom levels by
> upscaling lower
> zoom level ones at request time, thus avoiding to fill up the caches
> with upscaled data.
> Note that the RFC also provisions the usage of proxying these high
> zoom-level tiles to the source WMS instead of reconstructing
> them from
> the lower level tiles (use-case: the WMS is fast enough when
> but needs caching when far away). This isn't implemented yet,
> but should
> be a contribution by the OpenWebBlobe folks in some future.
> Hi Thomas,
> I have a couple of questions, probably not enough coffee to get my
> brain turned on yet.
> Your goal is to produce up sampled tiles from tiles at the “maximum
> cached level” using the reassemble strategy.
> So if that is level 15, then at 14 each tile would need to resample
> 4 tiles, and at 13 need to resample 16 tiles, and at 12 need to
> resample 64 tiles, etc.
> And these re-sampled tiles are not going to be stored in the cache?
> I can understand that if this resampling is fast that that would
> make sense, but it would seem to me that at some point the disk IO
> would start to kill this not to mention the CPU load. Why would you
> not want to store these tiles or take a hybrid approach and save
> every 2nd or 4th level above the max as a compromise between storage
> and performance?
> Am I missing something obvious here?
> -Steve W
> mapserver-dev mailing list
> mapserver-dev at lists.osgeo.org <mailto:mapserver-dev at lists.osgeo.org>
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