You just lay them out sequentially in whatever format your graphics library calls for. The only trick is that you need a table somewhere that tells you the offset, size, and so forth of each texture tile. Given that, you can figure out the offset and convert that to a pointer of the appropriate type. (Let's hear it for C and C++'s ability to casually convert types back and forth.)
Ok it's probably best if I describe what I'm doing now in detail. So we have a bunch of tiles that each represents about 400 square meters of the earth. The tiles are seperated by
UTM Zones and then by divisions of these UTM zones I call subzones. Each subzone gets it's own file in the database directory. Within each subzone file there is a list of tiles (by x,y,z) in that subzone along with the file offset information into a larger file. The larger file is just a huge collection of bitmap tiles. So when the program renders a map it finds the subzone files it needs to use, loads them into a cache and then using the subzone file information to seek to the right place in the large image file. Then it reads the bitmap from the image file and displays it on the screen.
So I think I'm doing this in a pretty efficient way already. What I was hoping was that there was some storage engine out there that would be just as fast and would handle all these file I/O internals for me. That may be wishful thinking though.
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