Thursday, May 31, 2007

Look Mom, No Tiles

Since before I've been involved in X-Plane, scenery has been broken into tiles. You know the naming scheme...+42-072.XXX is some kind of file for Boston. Perhaps it's a .env or a .dsf, but what is unchanged is that the world is broken up into bite-sized pieces.

Tiling is very necessary for X-Plane...it allows the sim to rapidly load only the information we are interested in. The world is too big to go fishing for the relatively small amount of data that is loaded at one time.

The source data that is used to build global scenery is also tiled - if you look at the SRTM files, they often have names like N42W072. It's no surprise that global data requires tiling to make it manageable.

When we produce global scenery, we work on a per-tile basis. We load the raw tiled data* into source XES files (one per tile), then process and convert that XES file into a DSF. By working one tile at a time, we limit how much RAM we need.

But if you used WorldMaker on an airport or city that spanned a tile boundary, you know how annoying tiling can be. With WorldMaker you couldn't see both halves of an airport at once.

WED will not use tiles. For custom scenery packages, the total data is not so large that we have to tile. When you work on a scenery package in WED, you work on the entire package at once as a single seamless workspace. When you export your work, WED will split the data into tiles as needed. This will mean:
  • You do not have to decide in advance where you are going to work. All scenery packages cover the entire planet, and DSFs are created only as needed.
  • You will be able to work on more than one "tile" of area at a time, because there are no tiles.
  • You will be able to work on airports that span tile boundaries seamlessly.

1 comment:

SteelBlades said...

All this talk of WED; it's getting exciting!