I'm not sure that I understand why you would want "level of detail"
functionality to reside in the rendering at the browser. This should
probably be handled on the server side not the client side. Why download
several levels of detail and tie up scarce bandwidth?
If level of detail is important to your application you could use a
spatial database for the maps on the server side. You can then handle lod in
a couple of ways.
1. Query using a simplify function filter. This would require some
javascript to identify a lod threshold as well as the aoi. Then the svg view
object would be changed to a new view object based on the results of your
spatial query.
2. Keep a detail level as a column in the spatial table and limiting
the query to the level appropriate to the viewbox. Again you would use
javascript to monitor the onzoom events.
For example: level 1 includes just highways level 2 includes roads as well
as level 1, etc If scale discrepancies exist you would probably not be able
to use a clause like "and level<=3" Another approach is to keep a min and
max visibility threshold for each object in the table then the query would
add a clause like "and (visibility>min and visibility<=max)" This approach
allows you to handle scale discrepancy issues by setting the min and max
thresholds to eliminate coarse scale when moving to finer scale or keeping
both if scale discrepancy is not an issue.
If you don't have a spatial database you could simulate one by dividing the
view into the various level of detail (one svgz for each) and calling them
with javascript from the onzoom event which detect when a specific level of
detail threshold has been reached. This could get complicated in a hurry
though and does not save much download time at the higher levels of detail
unless you go further and come up with a tiling mechanism too. In which case
as you zoom down, the lod svgz files are divided into horizontal tiles and
only the required tiles are merged to replace your svg view object src.
Obviously the database approach is cleaner.
By the way there is lod built into the renderer since objects have to be
mapped to screen pixels which automatically reduces detail intricacy. I
assume that is not what you want though.
Trying to include lod in the renderer doesn't seem like a good idea.
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