Open Source Simulator FlightGear Releases v2.4 70
mikejuk writes "The latest version of FlightGear, 2.4, has just been released — and it has some significant improvements. Now it simulates weather so that you can ride the up draft from a range of hills and seek out thermals — but watch out for the simulated fog! For the future the implementation of an HLA interface means that you can build clusters of interacting simulators and perhaps even work with commercial flight simulators." The FlightGear website has gotten a long-deserved upgrade, too.
Comment removed (Score:4, Insightful)
Re:Graphics artifacts (Score:5, Insightful)
While there isn't a lot of research on the topic, what there is seems to indicate that open source software and "commercial" (i.e. not open source) software have similar defect densities. Here's a paper on the topic:
http://www.reasoning.com/pdf/MySQL_White_Paper.pdf [reasoning.com]
I've worked on both "commercial" projects and opens source projects. My personal experience has been that willingness to fix bugs is much higher on the open source teams. Usually the authors actually use the product in their everyday life and bugs affect them personally. They are highly motivated to fix them. On "commercial" software projects, my experience is that the authors of the software rarely use it in their every day life. Selection of bugs to fix usually comes from a project manager.
Both open source and "commercial" projects usually have large backlogs of bugs that never get fixed. The difference is that open source projects usually fix bugs that directly affect the authors, while "commercial" projects fix bugs that directly affect customers who have bought enough units to gain the right to complain (i.e. thousands of copies). However, with an open source project, if the authors decide not to fix a bug you usually have a number of options. You can complain on the developer's mailing list and plead your case. If that doesn't work, you can fix the bug yourself, or hire someone else to do it. With "commercial" software once you file your bug you usually don't even know if they will decide to fix it. You usually don't even know if it was fixed in the next version without buying it and trying it for yourself. If the program manager decides not to fix your bug, you have no recourse at all unless you have already bought thousands of copies of the software and can threaten not to upgrade to the next version unless they fix your bug. Even then they might decide not to.
"Well that's the thing with volunteer made software isn't it?" is what you wrote. Yes. That's the thing with volunteer made software. You have direct access to the developers to report your bug. You get informed whether your bug when your bug is being looked at. You can make a case for having your bug fixed. And if that doesn't work, you can fix it yourself. What is there that needs fixing again?
Re:PC Based Flight Simulators just dont cut it (Score:2, Insightful)
Essentially what X-Plane does could be considered an extremely crude, low-density real-time CFD (computational fluid dynamics.) The problem is that even extremely well done CFD's that run offline on super computer clusters can't compute all the effects and aerodynamic interactions of an airframe. X-Plane is pretty good for what it does, and it's been tweaked and refined over the years to account for a lot of different effects ... but at the end of the day, "blade element theory" is a fancy word for "really crude CFD".
On the flip side, I don't know why people knock table driven models (except for maybe that Microsoft game them a bad name.) Very serious aeronautical engineers seem to prefer this approach because it's a way you can deterministically represent everything you know about exactly how an airplane behaves.
The problem with things like blade-element theory is that after punching in all the physical geometry of the airplane, if it doesn't fly right what do you do? Basically you start fudging the mass and geometry and using other tricks to try to get it to fly right ... not exactly science.
Blade-element theory might be decent if you have a brand new design and you have no idea how it will fly and you want to see approximately what might happen. But then if you decide to stake your life on the results, good luck to you!
There is a lot of FUD that gets spread about different simulators and how they model flight dynamics.
Here is another thing to consider ... blade element theory is kind of a cookie cutter approach ... it makes many assumptions and often you end up with all the airplanes flying roughly the same, just with the speeds and weights scaled differently. Once you get the hang of flying one of them, all you have to do is scale your basic piloting strategies to the speeds of the other aircraft and you pretty much have them handled. It's really hard to account for specific bad habits and flight regimes that cause specific problems for specific airplanes. Table driven models can actually account for the idiosyncracies of individual aircraft if you know what you are doing.
Remember, table driven models are just as physics based as blade element theory. There is a physics engine at the heart of them that is integrating forces and accelerations and computing velocities and rotations and positions ... all based on accurate physics and sometimes some very advanced numerical integration schemes. The difference is that the tables represent how to compute what the actual forces and moments are in any situation, rather than estimating them the way blade element theory does.
Anyway, I don't want to take away from the effort that X-Plane has put in to creating a nice sim, but much of the hoopla about blade element theory is exactly that ... marketing hoopla that gets repeated over and over and over again so many times I almost want to believe it myself! :-)