[OpenLayers-Dev] final animated zooming and panning patches

[Paul Spencer]

Sorry, I'll try to explain more ...  Now using the controls  
example ... I'm only using the mouse wheel to zoom one step at a  
time.  By the 3rd step, it is slowing down and by the fifth it causes  
100% processor usage for several seconds to complete the one step zoom.

Browser is Safari, hardware is a powerbook g4.

In Firefox, it is much better and rarely shows the really blurry  
tiles (or briefly enough that I can't get a screencapture of it anyway).

Digging a bit deeper ...

initial load: 4 tiles
zoom 1: 10 tiles
zoom 2: 30 tiles
zoom 3: 44 tiles
zoom 4: 50 tiles
zoom 5: 51 tiles
zoom 6: 60 tiles

Each zoom was a single step zooming in using the mouse wheel.   
Initially I thought it was keeping all the tiles from a previous zoom  
level but it actually seems pretty random to me.  Some of the images  
are definitely from other scales though and I think the blurry image  
is a symptom of those images being left in the dom tree and being  
scaled way beyond what they should be.  I haven't looked in the code,  
but I expect it is a leak of some sort that leaves these tiles in the  
dom after a smooth zoom.  This theory also explains why performance  
tails off quickly as I zoom ... more and more images to resize over  
time.

Cheers

Paul
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On 29-Mar-07, at 9:49 AM, Emanuel Sch?tze wrote:

> Hi Paul,
>
> I'm not exactly sure what do you mean.
> If you start the demo; zoom f.e. to level 5 and you drag now the  
> slider to
> level 0 you get a new zoomOut tile which show you new informations  
> arround
> the last viewport of level 5. This zoomOut tile is 4 times greater  
> than a
> standard tile and it contains the max extent. So it comes to some  
> alleged
> strange situations if you zoom out from a high level. After mouseUp  
> the
> zoomOut tile stay pixelated until the new tiles are loaded. This is  
> a normal
> zoom out process. Sure, we could improve it but therefor you have  
> to load
> more zoomOut tiles which scales in higher levels - and this could  
> be evoke
> new performance problems.
>
> To improve your own performance try to make your map smaller. My  
> demo has a
> map with 100% width; dependent on your screen resolution there are  
> many tiles
> which have to scale. Perhaps there is the bad performance effect if  
> the tile
> size over 32768px like in IE? Which browser and hardware do you  
> use? I can't
> reproduce these effects on my machines. Try the controls example  
> [1]. It
> should works faster.
>
> Regards,
> Emanuel
>
> [1]http://dev.openlayers.org/sandbox/emanuel/animatedZooming/ 
> examples/controls.html
>
> On Thursday 29 March 2007 15:10, Paul Spencer wrote:
>> Hi Emanuel,
>>
>> I just tried this out for the first time and its quite good :)  I
>> have one piece of feedback.  In all browsers (although perhaps Safari
>> is the worst), there is a strange visual effect after it has scaled
>> the tiles and before the new tiles arrive, some (or all perhaps) of
>> the tiles change to a very blurry image ... its very pixelated, each
>> pixel looks like it is about 50 square pixels on my screen.  This
>> doesn't happen right away, only after I have zoomed in a few times.
>>
>> Also, after a few zooms, the whole thing slows down to the point of
>> being not useful anymore and jacks my processor through the roof ...
>> at this point, even resizing the window is horribly slow and consumes
>> a lot of processing power.  I've attached a screen grab of the blurry
>> stuff that happens on zoom out.
>>
>> It does work great when first opened, though, so hopefully its
>> fixable :)
>>
>> Cheers
>>
>> Paul

+-----------------------------------------------------------------+
|Paul Spencer                          pspencer at dmsolutions.ca    |
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|Chief Technology Officer                                         |
|DM Solutions Group Inc                http://www.dmsolutions.ca/ |
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