Hi Dylan,
SVG viewers have their limitation and as far as I know, SVG was never
designed to handle huge amounts of data. Of course it would be nice if
it could ...
Parts of the reason of why it can't handle huge amounts of data are the
interactivity and animation features SVG provides. It has to maintain
the DOM for all the elements, which is expensive.
The threshold value of the number of elements that a viewer can handle
varies according to the hardware and the software implementation. It
maybe at 10000 elements up to 50000 elements. I never saw a SVG
implementation that could handle >50000 elements without performance
problems and many viewers already fail with 10000 elements.
There might be workarounds, though:
* use a clever serverside generation in combination with network requests
- if you want to show an overview of your data, just show the most
prominent features or aggregate features that are close to each other
- if the user zooms in, provide additional graphics or details
as an example see our yosemite maps
(http://www.carto.net/williams/yosemite/), which works in all SVG full
viewers, even if they don't support a large number of elements. Content
is generated serverside according to the map extent the user had chosen.
If a user zooms in, he gets additional elements and the geometry is more
detailed, as he zooms out, geometry is simplified on the server,
selected, partially aggregated or we use different datasets.
* try to reduce the number of elements. As an example: if several
circles share the same attributes/interactivity it might be more
efficient to use a path element with lots of "M" moveto commands and use
markers to show the circles. If you have lots of path elements, try to
aggregate them to viewer path elements.
* use elements are usually in particular slow. If you can use rects or
circles instead of the use elements, thats in almost all cases more
efficient than use elements
If you don't need the interactivity, other technologies (e.g. raster
graphics) might be more suitable, but as I see, you use the mouse
events, so this might not be an option.
* finally: if you really need to support such a large number of
elements, try to support SVG viewer development either by contributing
suggestions to improve the code, contributing code or helping
financially by supporting developers. I don't know if that is an option.
I produced a document that describes server-client communication for
maps and contains suggestions/ideas to improve performance. I don't know
if that helps:
http://www.carto.net/papers/svg/postgis_geturl_xmlhttprequest/
Andreas
Dylan Browne wrote:
Hi,
I guess this is a general question that I'm sure all SVG developers
come across, how to handle an SVG Document that contains a very large
number of SVG Elements.
I've scanned the archives but didn't see anything that relates to my
current issue, that is displaying a large number of elements AND those
elements containing a great deal of information.
For example, as below, this is my code to render a single circle on a
graph, together with it's associated JS etc. None of the information
is redundant, as far as I can see. I was wondering if there is any way
to 'compress' this, if that makes sense. I could conceivably need to
generate 50,000 of these circular points, by which time the Document
is getting bloated and giving outOfMemory errors. (I'm using Batik DOM
to generate my SVG Document in memory and then streaming it to a
browser).
<use fill-opacity="0.2" xmlns:xlink="http://www.w3.org/1999/xlink";
onmousedown="select_group(evt,true,145.94715733333334,445.35867495591333,'1.0');"
stroke="blue" name="1.0"
onmouseover="selectLabelledLine(evt,'DOSE =
10.00|IRESP = 42.91|ID = 1.0');select_point(evt);"
transform="translate(145.94715733333334,445.35867495591333)scale(5.0)"
width="5.0%" xlink:show="embed" xlink:type="simple"
fill="blue"
onmouseup="deselect_group(evt,true,'1.0');"
height="5.0%"
onmouseout="deselectLabelledLine(evt);deselect_point(evt);deselect_group(evt,true,'1.0');"
xlink:href="#circle" xlink:actuate="onLoad"/>
Thanks in advance for any advice,
Kind regards,
Dylan
--
----------------------------------------------
Andreas Neumann
Institute of Cartography
ETH Zurich
Wolfgang-Paulistrasse 15
CH-8093 Zurich, Switzerland
Phone: ++41-44-633 3031, Fax: ++41-44-633 1153
e-mail: [EMAIL PROTECTED]
www: http://www.carto.net/neumann/
SVG.Open: http://www.svgopen.org/
Carto.net: http://www.carto.net/
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