[mapguide-internals] RFC required for tile caching changes?

[Traian Stanev]

Can you also give an example for tiles with negative indices?
For example if in the current scheme the tile is -33, -64, what would be the resulting directory path?
 
R-2/C-3/-3_-4
 
What about tile -1,-1
 
Another suggestion I have -- name the folder part of the path (30 * tile index div 30) and then the file part would be (tile index mod 30).
 
So for tile 33,64 the folder would be:
 
Base Layer Group/30/60/3_4.png
 
And for tile -33,-64 the folder would be:
 
Base Layer Group/-30/-60/-3_-4.png
 
For tile 1,1, the folder would be:
 
Base Layer Group/0/0/1_1.png
 
For tile -1,-1 the folder would be:
 
Base Layer Group/-0/-0/-1_-1.png
 
 
It's a little weird around 0, but it allows for arbitrary groupings of tiles in folders (they don't have to be 30x30) since the tile index can be computed directly from the file path, by adding the folder term to the file path term.
 
Also, can you tell us what the problem is with having too many images in one directory? Is it a file system issue? And how many tiles is the limit, i.e. why is 30x30 the preferred grouping and not 1000x1000 for example?
 
Traian

	-----Original Message----- 
	From: mapguide-internals-bounces at lists.osgeo.org on behalf of Jason Birch 
	Sent: Fri 1/12/2007 8:57 PM 
	To: MapGuide Internals Mail List 
	Cc: 
	Subject: RE: [mapguide-internals] RFC required for tile caching changes?
	
	
	Can I forward this to the "tiling" list for comment?
	 
	

  _____  

	From: mapguide-internals-bounces at lists.osgeo.org on behalf of Chris Claydon
	Sent: Fri 2007-01-12 12:24 PM
	To: MapGuide Internals Mail List
	Subject: RE: [mapguide-internals] RFC required for tile caching changes?
	
	

	A sample tile location would be as follows:

	 

	……\ Repositories\TileCache\Samples_Sheboygan_Maps_Sheboygan\7\Base Layer Group\R2\C3\3_4.png

	 

	The R and C indices correspond to rows and columns where each row contains 30 tiles vertically and each column contains 30 tiles horizontally.

	 

	This indicates that:

	 

	1)       We’re at zoom level 7

	2)       We’re in grouped row 2

	3)       We’re in grouped column 3

	4)       The tile location within this grouped row/column combination is (3,4).

	 

	The R and C indices never take a zero value (to avoid issues with negative values around the origin), so this tile corresponds to a location of (33, 64) in the old scheme.

	 

	I took a quick look at the Tile Map Service Specification, but it doesn’t appear to support the concept of grouping blocks of tiles into subfolders in its current form. Can you provide more information on whether this is possible?

	 

	Chris.

	 

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