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Compatibility issues

The information and algorithms presented in this document apply to FS5.1 and were tested using FS5.1(CD version). FS5.1 has a wider set of instructions than FS5.0. Also, some instructions perform in a slightly different way in these FS versions. I made no efforts to highlight FS5.1 specific features. Thus, all code and suggestions should be tested on FS5.0 before using them for designing FS5.0 compatible sceneries.

Questions about FS6

One question that causes much concern among scenery designers at the time this document is written is whether BGL scenery files will be compatible with the upcoming FS6. The opinion presented below will be outdated as more information about FS6 will become available.

The only thing we now know for sure is that we do not know how compatible to existing add-ons FS6 will be. Microsoft has indicated that FS6 will be compatible to existing commercial add-ons, but not to all home-made stuff. Two questions arise: whether the scenery design effort for FS5 should be continued and how to write FS6compatible scenery.

The answer to the first question is definitely yes. If FS6 will be incompatible with existing sceneries, we can simply continue running FS5 when using them. There is also a possibility that the scenery that will come with FS6 will be so good that we will not want to use old sceneries at all. However, this could also be the case if FS6 would be 100%-compatible to FS5 stuff. Also, much time can pass until scenery design tools for FS6 will appear, if it is going to happen at all. Thus, the suspected but unproven incompatibility of FS6 should not discourage anyone from designing scenery for FS5.

The answer to the second question is much more difficult. The answer here depends on how Microsoft understands the 'compatibility' with existing commercial sceneries.

If this compatibility means we could simply install BGL files into FS6 and use them, then using only instructions, variables and algorithms actually found in commercial sceneries would somehow increase the chances that the home-made scenery will run under FS6 too. Another possible scenario is that Microsoft will publish updates that will make existing commercial sceneries FS6-compatible. This was the case with FS5.1CD: existing sceneries caused double runways and some other problems with the CD scenery, so the CD-ROM includes patches that fixed these problems. If this scenario proves to be true, there will be not much hope that even sceneries that only use "official" methods will be FS6-compatible. Microsoft could even change the scenery file format completely - and publish new scenery files for all its add-ons. They would easily fit on the same CD as FS6 itself.

A third scenario is that FS6 will be 100% compatible to existing sceneries, so all existing BGL files will run ok.

My opinion is that the second scenario is the most likely one to happen. Thus, also tricks not found in commercial sceneries can be used without any special concerns. The information in this file does not restrict itself on tricks actually found in commercial sceneries.

My thoughts about FS6 are based on speculations, not on facts. As can be seen, the risk of either designing incompatible scenery that could otherwise be compatible or restricting the tricks used without any gained compatibility cannot be avoided. So each scenery designer should decide for himself, which line to follow.