Basic facts about the Flight Simulator, Scenery design and Swedflight - by Bo Wiberg 

History

For those of you who were lucky enough to own a computer already back in 1979, you may remember what sensation the appearance of the very first version of the Flight Simulator made. It's father was Bruce Artwick at SubLogic Corp. Produced in the beginning for the AppleII (with only 16 kb memory!!) - the first really successful home computer - it was later transformed to the PC environment after IBM had released their Personal Computer in 1983. Already at that time it utilized the computer hardware extensively and for a long row of years the Flight Simulator became the test of choice to check if a new computer was IBM compatible or not. Even if it used the hardware to the limit the appearance on the screen was very rough, with the world represented as a grid only, the panel quite primitive and with an aircraft that was almost impossible to land (at least for me). Yet it soon became the most sold of all 'games' - which it was called then. The reasons for the great success was because you could definitely feel the fascination of flying already in this early version and that you here for the first time saw a form of real world simulation realized on a simple home computer. 

Two pictures from one of the first versions of the Flight Simulator. The world was represented by a grid only. No textures and very few objects. The airports had no more details than the simple runways. But already you can recognize the layout of many of today’s instrument on the panel.

But the development went on and I can still remember the thrill when version 4 much later was released. Now everything was in bright colors, there existed a more 'realistic' world and you could land the aircraft with a reasonable real feeling. And among all, you could buy a separate editor and make your own airports and for the first time modify the default sceneries a little. But the efforts from those who tried to make something of their own were not so many and it was not easy to find them. 

The Flight Simulator of today is a highly sophisticated program that probably will be certified as a tool to be used at flight schools for navigation training. Even if several other simulators have been released during the last year, to us old-timers in the flight sim world this old-timer of program (19 years old!!) still is number one. The new ones maybe more flashy and more advanced, but no other simulator can offer the user all those hundreds of freeware sceneries, thousands of extra aircraft plus panels, all those extra freeware, shareware and commercial utilities for route planning, adventures etc. Plus the fantastic possibility to be able to construct it yourself like we have done in the Swedflight group. 

Stockholm/Arlanda airport from Swedflight 2. A very realistic environment both outside and inside the aircraft. The simulator of today is an almost certified tool for navigation training. (The panel is made by Eric Ernst.)
 
 

Freeware sceneries

The many freeware sceneries that you can easily find today on the Net and elsewhere are the result of three factors. First came the totally new version 5.0/5.1 of the Flight Simulator with a new internal construction of the program. Then after a while appeared the basic document that was released in 1995-96 by Maurizio Gavioli (and others) that for the first time revealed most of the secrets about the program build up. This was the united result of many peoples intelligent ‘hacking’ into the BGL:s and other files that belong to the simulator. The disclosure of the internal structure of the BGL file led to a fast release of several freeware compilators by which it became possible to make your own scenery files. The development of a lot of freeware (and commercial) sceneries exploded literally and today they cover a big part of the earth. The last, but not least, reason to this explosion is the widespread use of the Internet where the Flight Sim pages have a big amount of visits. 
 
 

Swedflight and scenery design in general

The origin of Swedflight is a scenery made by Bengt Larsson in 1995, called Swedmap. It was maybe one of the first of all freeware sceneries covering a whole country with great detail and exactness already from the very beginning (even if it used another scenery to add all the airports in it). Bengt Larsson is also one of the three authors (the other two are from Norway) of the now famous and awarded Norway scenery and when version 6.1 of that was ready, Bengt formed a group with three other Swedish guys to make a similar, detailed scenery for Sweden - and that resulted after half a years work in Swedflight, released September 1, 1997. At that time a lot of new tools had reached the market, and we used from the beginning a freeware program by Peter Jacobson, called ScBuild. This was a really revolutionary product that made it possible to make big sceneries relatively easy in a reasonable short time. Without that program it had not been possible to make Swedflight 1.0 in ‘only’ a little more than six month. ScBuild became later the commercial product ASD (Airport & Scenery Designer) which we now use instead. The compilator to make the final BGL files is in our case SCASM32 by Manfred Moldenhauer, also a very powerful product. 

The main goal when we started the Swedflight project was (and still is) to make a scenery as much detailed as is possible today, without sacrificing the most important feature in a flight sim scenery - the frame rate. That was maybe a little more necessary when we started the project, because of the much slower computers that were around at that time. But even today, when the Pentiums are more or less a standard, it is a necessity. A detailed scenery with a lot of 2D and 3D objects, for example a big airport in a complex surrounding, still puts an extremely heavy demand on the computer and the graphic hardware. 

An aerial view from Stockholm/Arlanda. This type of scenery is very demanding and when you construct it you must give all objects proper visibility settings to achieve a reasonable frame rate. Furthermore you must put the objects in different complexity layers suitable for fast and slow computers. 

It is today possible to make a scenery with extreme exactness, and we sometimes get questions why we don’t make a special object or area more detailed than we have done in Swedflight. A small lake, for example, can in our case be represented by a polygon with only 4-5 points, instead of maybe 20, which would be more realistic and possible. The answer is again - frame rate. 

To understand that and for those of you that are not familiar with the build up of a scenery I want to explain shortly how a scenery is constructed. The main building blocks in a scenery are four elements: Tiles, 2D objects, 3D objects and Textures. 

• The base or ground, so to say, in a scenery is defined as a grid, forming square ‘tiles’ that cover the whole earth to max. 89 degrees 30 minutes (South or North). You can imagine the earth as a bent cylinder with 8192x4096 square tiles on which you can build your scenery. Each of those tiles you have to give a certain height and that will represent the different ground levels in the scenery. 
  
• On those tiles with their defined heights you start placing your 2D objects. Those are everything that have only two dimensions: coastline polygons, lakes, islands, smaller or bigger communities, roads, rivers and all other 2D polygons (swamps, parking places, beaches etc.). Every time a polygon is to be presented on the graphic screen, the program must do a calculation of its size and form. If you have many points in the polygon or if you have a lot of polygons at the same time on the screen, the computer must do an awful amount of calculations every time the screen is updated and when you move through the scenery. You can construct your 2D map totally freely or you can, as we did, use some of the digital chart databases that exist on the Net, and import the contours of the landscape into your design program. Mostly that picture is too detailed to be possible to use directly so you have to make it much simpler. It is a pity of course, but the frame rate is so important that you must sacrifice detail to gain speed. This is one of the features that are the hallmark of the good design philosophy, that Bengt Larsson and some more pioneers in scenery design have ‘preached’ for a long time. And that philosophy is still valid in spite of faster computers. 
  
• To make it even more complicated for the computer you can also define 3D objects: mountains, houses and all sorts of objects that you can think of and imagine. The calculations for those are a lot more demanding than for 2D objects. The biggest paradox in scenery design appears at an airport. An airport is often the most complicated area in every scenery because of its many 3D objects and the surroundings that often have a lot of 2D objects (cities, roads, rivers, islands, you name it). The paradox comes from the need for speed in the program at an airport and the need for maximum number of objects at the same time. To be able to land an aircraft with good precision and a real feeling of flying the aircraft you need as high frame rate as possible - 6-8 frames/sec is an absolute minimum for some realism. That figure is not easy to achieve if the airport contains a lot of objects. You can find many airports on the Net where it is almost impossible to land because of the slow frame rate. It works maybe if you have a 200MHz Pentium or faster, but not all are lucky to own such a machine yet. One of the tricks you must use then is an internal programming variable called visibility. Most objects at an airport you can give very short visibility and that speeds up the calculations and the frame rate considerably. This is also a part of the good design philosophy. 
  
• The fourth element is textures. A texture is a graphic picture in the form of a bitmap that is projected on the surface of the tile, 2D or 3D object. You can imagine it as different ‘wallpapers’ that you put on the surfaces of all the objects in the scenery. The quality of the texture is extremely important for the final look of the scenery. Microsoft has delivered a default set of textures with every version of the simulator, but a lot of those don’t look very Swedish or even European. Therefore we decided to make a totally new set of Swedish/Scandinavian looking textures that would give Swedflight a defined Nordic look. The design of a texture is an art in itself but we have mainly based our textures on aerial photos from different parts of Sweden, also those that are used for the winter setting. One common problem with all textures used for the ground tiles is that you very easy can see the borders between each tile. That gives the landscape a chess board look, especially when seen from bigger heights. We have tried to minimize that effect by using two special tricks, maybe invented by us. Those tricks you can easily find out if you study the build up of some of our texture files. 

View from the surroundings of the airport at Angelholm showing the use of one of our special 'seamless' ground textures (Prairie.r8) 
 
 

The future of Swedflight and other sceneries

The development of the hardware is accelerating at a faster speed than ever and that will of course result in the possibility to make better sceneries in the near? future. Already you can for example implement a much better graphic by using the latest 3D graphic boards. That gives the existing textures a realistic look that can be even more enhanced if you optimize the textures for 3D use, like the ones Microsoft made for FS98 as a second default type. Maybe Microsoft will also reveal some secrets about the internal build of the simulator. Now at last they have started to give away a series of development tools for the simulator, which we designers appreciate very much. The Design Kit for panels is already out and they have promised more tools in the near future. What that can mean for the development of freeware sceneries we can only guess for the moment. A totally different path to choose in scenery building is to make a photorealistic scenery by putting a series of photographic texture files side by side. Such sceneries have existed for a long time but are now beginning to show up more frequently. But they use a big disk space of course and to construct them you need a lot of good aerial pictures, not so easy for everyone interested to get hold of. The existing photorealistic sceneries cover also only small areas, but the result is very good as you can see also in FS95/98 where the Las Vegas scenery is such an example. 

Swedflight will also be developed continuously in the future. Now when the geography is more or less ready in version 2.0 we will put a lot of effort in making the airports as realistic as possible. A big job because we have about 180 airports to take care of, some are very simple but the big ones need a lot of constructive work. In that job we rely on the help from many interested people around the country that send us pictures and data about airports in their neighborhood. Without their kind support the realism of the airports will suffer. One of the stimulating parts of scenery design is this almost daily contact with many of the users of the scenery. So don’t hesitate to call us (by e-mail) if you feel that you will discuss some features or problems in Swedflight or of course if you are willing to help us with pictures or data so that we can build the airports of Sweden as realistic as we want and intend to. Another part of the update process will be to develop the textures more and more. The look of a scenery depends in the end almost solely on the look and quality of the textures used. Therefore we will put a lot of work also into this important part of flight sim design. 

Author: Bosse Wiberg/Swedflight (May 1998) 
 
 

The drawing and the resulting map showing the use and effects of 3D objects (mountains) in the High Coast area of northern Sweden
 
 

The aerial view of the landscape from the drawing above (showing the birthplace of the author actually)

Copyright 1998, SWEDFLIGHT