= !MapGuide RFC 90 - Meta Tiling Support =

This page contains an change request (RFC) for the !MapGuide Open Source project.
More !MapGuide RFCs can be found on the [wiki:MapGuideRfcs RFCs] page.


== Status ==

||RFC Template Version||(1.0)||
||Submission Date||(Date/Time submitted)||
||Last Modified||(your name here) [[Timestamp]]||
||Author||Zac Spitzer, Uv ||
||RFC Status||(draft)||
||Implementation Status||(testing sandbox)||
||Proposed Milestone||(2.2)||
||Assigned PSC guide(s)||(when determined)||
||'''Voting History'''||(vote date)||
||no vote|| ||

== Overview ==

Add support internally to the MapGuide Server Engine to render larger tiles
and then slice them up into the normal tile sizes

== Motivation ==

With complex maps, it's more efficent to render one large tile than many small ones. 
There is little or no benefit for simple maps like the Sheboygan Sample.[[BR]]

Using our 140 layer example map we can observer the following timing using metatilefactor 1 & 4
and 3 different locking strategies in the attached chart MetatilingChart1.jpg.

== Proposed Solution ==

Add a meta tile factor to the tile service, which then will render larger tiles
and then slice them up into the smaller tiles which get served to clients.

== Implications ==

The current approach with polling for lock files is inefficent and 
is excaerbated by meta tiling. When using a meta tiling factor of 4,
15 tiles will wait and poll for 1s while the meta tile is rendered
and sliced up.

Changing to a mutex would help

== Test Plan ==

The output of a tile map request should be indentical whether served 
with meta tiling enabled or without. 

== Funding/Resources ==

TBD

== Sandbox ==

http://trac.osgeo.org/mapguide/browser/sandbox/rfc90