FSLandClass

By Andrew Herd (15 March 2002)

icrosoft Flight Simulator draws its fair share of criticism, but one of its most impressive features is its chameleon like nature. Just when you think that you have seen it all, someone discovers another little tweak and everything changes, as if by magic. This article is about a tweak that can change the world, courtesy of a program called FSLandClass, developed by Burkhard Renk. But there is much more to it than that; the screen shots you see here wouldn't be the same without Ruud Faber's FScene, which will be the subject of a later review - and the star around which this particular show is based is Iain Gallacher's freeware Glasgow International Airport.

So what is the excitement all about, then? Well, a lot of scenery has done the rounds of my hard disk and it isn't often that I download an airport and do a double-take, but when I downloaded Iain's new package and spotted an FSLandClass file buried among the folders, curiosity overcame my natural sense of caution. Download the scenery and you will see why I am so impressed; the result of installing the complete scenery is nothing short of spectacular and one of the reasons for writing this piece is to highlight to developers the possibilities open to them if use FSLandClass.

FS2000 came with a new type of scenery called elevated mesh, which radically changed the look of the sim by introducing a more natural looking landscape. The quality of the mesh was much improved in FS2002, but despite this a major criticism of the sim has always been that the coverage of the mesh with textures was fixed and that there was no way to alter it. This wouldn't have mattered much except that Microsoft has made some strange choices of default texture coverage. Much of England is shown as open grassland, when in reality there is little lowland ground that isn't under tillage - no doubt simmers the world over stare at Flight Simulator from time to time and wonder why it is that being "as real as it gets" doesn't seem to include them.

But FS2000 did highlight the possibilities and after its release, developers put a great deal of effort went into working out where the information which coded for placement of textures was stored. After a great deal of trial and error, Burkhard found out that Flight Simulator stores such data in a special type of bgl file, which he calls a "landclass". A landclass file can be thought of as an overlay on top of the mesh terrain, the function of which is to tell Flight Simulator what the surface should look like at any given location. Given appropriate tools it is possible to create new landclass files which force the scenery engine to use specific textures in defined locations.

The effect of applying a new landclass file is best appreciated by seeing it in action. Look at the adjacent screen shot, ignoring the top picture for the moment. The only difference between the bottom two pictures is the new landclass file Iain Gallacher developed for his Glasgow airport scenery. If you click on the image and examine the full-size screen shots, the first thing you will notice is that the large area of heathland in the foreground of the middle shot is replaced by fields in the lower shot. Furthermore, while the built-up areas in the middle shot are confined to the upper third of the screen, the distribution in the lower shot is quite different, and much more realistic. The reason the lower shot looks the way it does is because Iain has spent countless hours creating a custom landclass file to make the towns and villages appear where they do in real life. To my eyes, that picture is as close to reality as I have yet seen in a simulator - it is how Britain looks from the air.

Before we go any further, I had better explain why there are three screen shots in each strip. The top shot is purely for reference and show the scenery as it appears in a clean install of Flight Simulator. The center shot shows what happens when the default textures have been replaced with Ruud Faber's FScene textures, which are much better suited to Europe than the ones Microsoft provides - Iain Gallacher's freeware Glasgow International airport has also been installed, which explains the appearance of the chimney. The lower shot is simply the second state, with Iain's custom-built FSLandClass file added, which has caused Flight Simulator's scenery engine to redistribute the textures. As you can see, the difference is quite spectacular.

FSLandClass is a 15 Mb download and costs 20 euros or $16. As has become the norm, it has an automatic installation routine, which worked very well, but before the software can be used it is necessary to download Microsoft's freeware terrain SDK, a link to which is on the site. After the SDK files are installed in the FSLandClass folder they can be forgotten about.

In a nutshell, FSLandClass can be thought of as a basic graphics editor with some clever file saving features. Once you have selected the coordinates of the area you want to work on, you can create a landclass for it from scratch, but this is a long and tedious process and the easiest way to get up and running is to buy one of Burkhard's "country packs". Packs covering the majority of Europe, the US and many others areas have already been released; these are intended to provide a start for designers, since most of the hard work has already been done. Essentially, the country packs are landclass files with every texture location precoded, based on data extracted from digital maps and they cost $12 each; though I should point out that complete coverage of the continental US requires the purchase of nine packs.

The FSLandClass program can be used to edit and compile the data from these files to produce very realistic representations of local scenery. In addition to encoding the textures needed to show the terrain (fields, woods, deserts, whatever), the landclass files in the country packs include every urban area with a population of 5000 or more and many towns with populations of 1000 to 5000, though most smaller villages aren't coded. In the FSLandClass editor, different types of texture are shown as different colored squares (dark green for forest, various shades of lighter green for fields, red for urban areas etc.); clicking on a square brings up a dialog showing the precise class of the texture.

If you don't fancy trying your hand at landclass editing, there is even a compiled landclass file included with each country pack, which is automatically recognised by Flight Simulator if it is installed in the correct folder. The availability of the country packs begs the question of why anyone should bother using the FSLandClass editor at all, but although the packs are 80% of the way there, if you want truly VFR scenery, a great deal of editing is going to be necessary, if only to add in all the smaller villages.

As it stands, the editor has plenty of rough edges and the kindest way of describing it is to say that it is more of a developer's than an end user's tool, but the way the FSLandClass program works is simplicity itself. Each Flight Simulator landclass tile is split into a grid of squares which are a little over a kilometre on a side, depending on latitude. Each square has a one byte code which describes not only the texture usage but also the autogen scenery it will display, which is how FS2002 manages to show all those buildings and trees without grinding to a complete halt. The secret of the FSLandClass is that it lets you alter the value of that byte. With a single click you can change a square kilometer from desert to golf course and back again, and if you select a texture which is associated with Autogen scenery, then that will appear when the landclass bgl is read by FS2002.

Once you have made the changes you want to a landclass file, options in the FSLandClass program allow you to compile and save it and you are ready for action. As you fly across the terrain, the scenery engine frantically reads the landclass files of the squares around you and builds that Autogen as fast as it can, at the same time as it figures out which texture to use. Neat, or what?

The best thing about landclass files is that they can be distributed as freeware, provided that one of the country kits isn't used for the basis of the scenery. Commercial developers should take note that the price of a country kit includes the right to sell up to 100 copies of that scenery. For every additional 100 sales, an extra copy of the country kit has to be purchased - though Burkhard is happy to talk about bulk deals.

Incidentally, it was while I was using FSLandClass that I finally realised why I sometimes see Autogen and sometimes don't in apparently similar areas. It all boils down to frame rate usage. Imagine a 1.4 Ghz Pentium with the FS2002 frame rate locked down to say 25 fps. Now fly over an area of flat ground with Autogen set to dense; the odds are that you will see plenty. If you then fly over an area of complex mesh terrain with a detailed airport in the middle of it, no Autogen appears, purely and simply because FS2002 only generates it when it calculates it has enough spare processor cycles to do it. Even I have to admit that Microsoft has been quite clever here.

So far, Burkhard hasn't figured out how to extract the information on texture type from the default landclass files supplied with Flight Simulator, which means that there is no way to exchange small groups of land class squares (for example, the immediate area surrounding an airfield). The biggest drawback to the program is, therefore, that it is only possible to edit a complete land class file, which means dealing with a predefined area of around 300 kilometres square. The example in the screen shot above includes most of northern England - the file being taken from the country pack for the Great Britain.

OK, I hear you say, no worries, I can just alter the area I want and forget about the rest - and you can. While I was writing this article I played around with the textures at Teesside, which is the red area about half way up the east coast on the screen shot above. Now imagine that I spent an entire weekend doing this (not difficult when you get going, since all it involves is a bit of pointing and clicking), getting the outlines of all the towns and villages and woods and everything just right. Then I save my work as a landclass bgl file and drop it into \FS2002\scenery.

There is therefore a potential problem if I want to install another landclass scenery later on that involves the same tile. For argument's sake, let's say someone else does a similar job on the area around Carlisle and sends me his work. Carlisle, for those of you unfortunate enough to live outside the northeast of England, is on the west coast, almost opposite Teesside - so any landclass edits there fall on the same tile as mine and if this is done the results can be unpredictible. However, Burkhard has thought of an extremely clever way around this.

Designers who wish to make landclass edits available for cooperative scenery designs can merge their work using two different methods. The first is, like FSLandClass itself, impressively simple. Every single edit made with FSLandClass is recorded in a text file with an .frc extension. If my friend sends me the frc file with his Carlisle edits, I can merge them with my Teesside edits, and create a new combined landclass file. The second method, slightly more complicated, is to use FSLandClass' facility to export and import class sceneries as bitmaps. So if my friend sends me a bitmap, I can copy and paste his areas into mine and merge the two using whichever graphics editor I choose. Editing exported bitmaps with a program like PhotoShop opens up an enormous range of possibilities - there is no reason for example, why one shouldn't scan a detailed map of a local area, edit the image using colors corresponding to the texture layers FSLandClass uses and then merge the result with an existing landclass file.

One look at the screen shots should be enough to convince most people that this is a ground breaking program. I can't recall seeing a single piece of software which had greater potential to alter Flight Simulator. I did run into a few problems while I was using FSLandClass, however. The first one was that there are two versions of the program, FSLandClass98 and FSLandClass2000 - the latter wouldn't run under Windows XP Professional no matter what I did - this is a known issue. The other issues are that the manual needs a complete rewrite and the interface is very clumsy, but believe me, once you understand how the software works, none of this matters.

FSLandClass is the most innovative piece of software I have seen for a very long time - it has the power to change the Flight Simulator world beyond recognition. I don't find it hard to imagine groups of freeware designers getting together to produce accurate landclass files for entire countries - the UK and the Netherlands are obvious choices that could be tackled relatively quickly. To see this application in action is to appreciate the breathtaking possibilities it offers and I would be very surprised if the majority of add-on sceneries aren't packaged with landclass files before very long.