World Wide Guide to FS Scenery Design | Knowledge Bank | Seeds

The story behind SEED textures

     (Note: This is a DRAFT document - Your comments are welcomed)

Flight Simulator offers two ways of creating landscapes:

• You can lay down synthetic tiles, whose colour and appearance can be determined either by the default texture files supplied with the FS package, or by special texture files you create.
• You can lay down a flat polygon and associate any texture file with the polygon.

This article looks at the first option, focusing on the special texture files you can create for use when covering a large area with synthetic tiles.

Why are they called "SEED" files?

These special texture files are called "SEED" files, because they are used to impregnate the FS scenery engine for easy "planting" and quick coverage of large areas. 

Although they don't offer the precision of placement that is possible with polygons, synthetic tiles using the default FS textures or your own SEED textures are the simplest way to cover a large area with scenery that approximates the actual appearance of that area. All the compilers allow you to lay synthetic tiles that make use of these textures,

Note that the default and SEED textures must be kept in the main TEXTURE directory, unlike other textures, which can be placed in a sub-directory holding files associated with a single scenery area. 

If you use the textures supplied with FS, you'll notice they have descriptive file names like NEEDLE.R8 (the pine forest), URBURB.R8 (suburbia), etc. Although some compilers allow you to specify such textures by their descriptive names, the internal FS engine itself refers to these standard textures by a hexadecimal number. For example, NEEDLE.R8 is identified in low-level computer code by the number 02; the farm is identified by the number 87; the city by 8C; etc.

How SEED files were discovered

Although the makers of FS have never documented the use of SEED textures, it didn't take scenery designers very long to discover that if you create your own 256-pixel-square texture file and name it SEEDxx.r8, you can use your own textures in synthetic tiles by specifying the hexadecimal number you used in your SEED file.

Several years ago, Bill Roccia of Philadelphia stumbled on to SEED possibilities by experimentation.

"I was experimenting with laying down synth blocks, and tried an undocumented number in the source code. Instead of the documented number 89, I tried 90. When I started FS, it said: "Can't find SEED90.R8!" So I found a way to lay down my own textures with the seed names. A lot of other people discovered the same thing at around the same time."

If you create a texture designed to simulate the appearance of a suburb where red roofs are common and you call the texture SEEDF4.R8, you can lay a synthetic tile featuring that texture by specifying F4 as the texture.

If you use a synthetic texture tile such as the Swamp (known to the FS scenery engine by the hexadecimal notation of 0Ah), the scenery engine automatically uses SWAMP.R8 to generate the texture. But if you specify a hex number that FS hasn't reserved for its own use, it will automatically append that number to the prefix SEED, and look in the TEXTURE directory for an .R8 file that matches that name.

Note that it is not possible to assign names to your own seed textures, in the same way that FS automatically associates "Swamp" with 0Ah. You have to stick with hex numbers when you're working with homemade SEED files.

The limitations of SEED files

The use of SEED files opens up a lot of possibilities for customised scenery, but poses some serious problems as well. The problems arise from the limitations on the number of textures.

Because it's a two-place hexadecimal number, there are 16 x 16, or 256, different numbers available. 28 are already programmed by the FS scenery engine for use, leaving 228 for custom use.

That's a goodly number, but there are several problems with using SEEDxx.R8 textures:

• Because they have to be in your main TEXTURE directory (unlike other textures which can be isolated in their own subdirectories), there's no way to activate or de-activate them with various scenery files. If you have some custom SEEDxx.R8 textures in your main TEXTURE directory and want to use a scenery created by another designer who created his own custom textures using the same names as you used, you have a problem.
• They suffer the same placement limitations as other synthetic tiles. That is, FS basically carves up the globe into numbered tile-size blocks, and you fill a tile by specifying a number. The smallest tiles will be 2-4 miles square, depending on latitude, so you can't use them to define precise landmarks in the scenery.

The advantages of SEED files

The arguments in favour of using SEEDxx.R8 textures include:

• They can be placed even in a basic compiler like BGLGEN, which doesn't support more advanced ways of laying custom textured terrain.
• They avoid the need to fiddle with polygon textures and complex code. Polygon textures are custom textures you lay using the various polygon commands found in the more advanced compilers.
• When large areas are involved, they may require less processing power and disk space than polygon textures.

In recent debates in flight-sim circles, some designers have urged their colleagues to avoid using SEEDxx.R8 textures and rely on polygon textures. Polygon textures allow greater authenticity of location, shape, size, seasonal variation and night-time lighting. It's worth noting that several kinds of polygon commands are available: in SCASM, for instance, it has been noted that Poly and TexWindow produce faster frame rates and better haze effects and are a better choice than TexPoly when it comes to 2-D texture surfaces.

Despite the limitations with SEED-based synthetic tiles, if you want to cover a large area quickly, and don't want to go to the trouble of creating custom textures laid down in polygon style, the SEED method may be a good approach.

With the help of numerous designers on the Flight-Sim mailing list, we've put together a registry of known SEED files. In the absence of a committee that might officially endorse a new SEED texture, we're proposing a set of guidelines to follow if you want to create a new SEED texture for use with scenery you distribute. And we're working on arrangements with the keepers of the FTP.IUP.EDU site for creation of a special storage place for SEED files.

See Registry of SEED Files

If you have anything to contribute on this subject,
please send e-mail to kraybill@vianet.net.au.