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Question for A/C developers: Anatomy of an FSX Aircraft

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I don't have any experience in desiging aircraft, sceneries, airports, or anything that goes in FSX. But I have a question about the anatomy of an FSX aircraft and how the different parts pertain to the a/c's overall performance.For my example I will use two aircraft that I get good performance overall in FSX: The LDS 767 and the Aerosoft F-16 that I got last week. For the most part I can fly these a/c into most parts of the FSX world and get good to great performace for the most part, even with full weather setting and AI. Having said that, I have read that some a/c have higher polygon counts than others. From what I understand is that every poly is like if you put an a/c under a microscope and look at it like a bunch of cells, each poly would be a cell for every curve, flat surface, etc. Basically, the polygons are like the terrain mesh of an a/c. Then the textures cover it and now you have a visual model instead of a bunch of sticks. From there you have the avionics, of which consume more processor and vid card time to compute then display the information. I understand that is why some a/c with glass panel displays may take more of a performance hit than an a/c like the default Cessna 152 with regular dial guages.Hopefully I understand this correctly to this point, or somewhat correctly. Because this is where my question comes in.In the model folder of my Aerosoft F-16 there are 3 files:F-16A USA_EXT_0.mdl 23,100 KBF-16a USA_INT_0.mdl 11,951 KBModel.cfg 1 KBAnd in the LDS-767 GE model folder:767300.mdl 8,833 KB767300_interior.mdl 2,183 KBmodel.cfg 1 KBNow, aside from the texture sizes and resolutions, differences in avionics, etc., based on the file sizes is it safe to say that the LDS 767 would have a smaller poly count and be less processor intensive than the F-16?The reason I am asking this is for two reasons.1. Say your not a screen shot artist and don't care what the outside of an a/c looks like, or you never view the a/c from the outside. If you wanted to get the absolute best performace out of an a/c for flying purposes would it be possible to just do away with the exterior model of an a/c? I mean, for myself since I fly only from the inside and don't take screen shots what is the benefit of having an elaborate external model.2. An example would be if your planing a flight into say a really busy airport like LAX or Heathrow and are goind to be only flying and not looking at the outside from spot view or any other outside views is it possible to exclude the exterior model? In this instance I wouldn't care if my LDS 767 looked like a low poly AI aircraft or even a school bus, as long as it looked like it should on the inside and the flight dynamics remaind true.Is this why people "merge" a panel from something like a PMDG to a POSKY model or something to that effect? If this is the case, is it possible to merge some of my more demanding a/c like the two mentioned above with other less demanding models like an AI F-16 model or my LDS 767 with an Aardvark AI 767 model that only has a model size of 535 KB?As I mentioned in the start, these two a/c offer really good performance for the most, but I am always looking to improve. It would make it less demanging on my system when I am trying to get into really big, detailed airports with loads of AI, if my own a/c wasn't consuming so much processor power. It seems like a waste of resources to have really detailed models if your like me and never step foot to the outside of the a/c to look at it. For me, its just about flying. I wouldn't even care if my a/c was invisible on the outside as long as the inside remained the same and it had contact points for the tires so could land, lol.I know this is probably a really weird question? But it's been something that I have been thinking about for a while. If its possible to do this I could eliminate my external models for serious flying and replace them when I am looling to do screen shots.Thanks in advance for any help on this.Sean

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Ron,This raises a question that I've always wondered about.Why do 3PDs not include in a typical aircraft release exactly what the OP is asking for ... a version of the aircraft that is ONLY a virtual cockpit, for those times when you desire very high performance?Thanks in advance for answering,

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>What a great idea! I never look at the outside view...I do all the time....Probably because I flew R/C for many years, and can easily keep the spot view aircraft in control :)Yet, while simming, realistic wing views are very important to me. If the wing looks lame, I won't bother with the model. Hundreds of my real life photo's include the wing in the pic. Therefor, a good portion of the wings, and fuse must be modeled well enough, to at least give me the feeling of being in a real aircraft.There is a lot of wing in this pic, but you'll get the idea :)L.Adamsonhttp://forums.avsim.net/user_files/194557.jpg

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True-and while I'll look outside only for the screen shot forum-why not include an "ifr" massive fps friendly view/aircraft selection that doesn't include all the outside stuff that gobbles up fps?GeofaMy blog:http://geofageofa.spaces.live.com/

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I guess this brings another thought to mind for me. Is the simulator effected by high poly count even if the outside view is not being rendered? I mean why would there be a performance hit for a high poly aircraft if the outside of the aircraft is not even in the view?

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Polygons facing away from the viewpoint are not processed by the video card so only about half the polys get rendered in an external view.Probably even fewer rendered on an internal view.

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Thanks for the replies guys.I have always wondered why two versions of the same a/c aren't usually offered by a developer. Like a hi-res/hi-poly version for screen shot use, then also a low or no poly version for just flying. Like Kevin mentioned, there are time perhaps the plane could be just a virtual cockpit to conserve on processing power. I know when I had FS9's PMDG 737NG they gave you the choice to load the plane with only 2-d cockpit, only 3-d cockpit, or with both, hence taking up more cpu power. I guess in FS9 even if you loaded that plane with both cockpits and didn't use the VC is was still consuming cpu power even though is wasn't being rendered.Ron, you replied yes. Can you give additional details. Does this mean that before I start a flight in say the LDS 767 I can just go into the model folder of that a/c and just move the exterior model file out for the flight? Is it as simple as that? Or can you just alias an external model from another aircraft like the Aardvark AI 767 to use? I would love to learn more about this so I can do the required modifications on a flight by flight basis and see how it goes.Thanks again.Sean

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Sean, I'm reticent to answer in detail because there is much that can go wrong or right depending on how things are constructed and whos hands are on the keyboard and mouse...You can experiment with configuration files and such but the best method is to have experienced hands who have good working knowledge of the sim and model parameters.Things to consider are wing views and other VC elements as well as proper configurations.Just a side note but we often introduce special parameters that cause certain polys/textures to represent zero footprint load factor to the sim while those parts are not in the users viewpoint.Bottom line is that 3PDs use a variety of techniques already and we're unsure that what you've asked would present a significant gain in performance but that would be determined on a case by case basis.:-)

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Larry, is that pic in Nevada?RhettFS box: E8500 (@ 3.80 ghz), AC Freezer 7 Pro, ASUS P5E3 Premium, BFG 8800GTX 756 (nVidia 169 WHQL), 4gb DDR3 1600 Patriot Cas7 7-7-7-20 (2T), PC Power 750, WD 150gb 10000rpm Raptor, Seagate 500gb, Silverstone TJ09 case, Vista Ultimate 64ASX Client: AMD 3700+ (@ 2.6 ghz), 7800GT

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You can keep your external model from ever being loaded into the sim by commenting out the relevant section of that model's model.cfg file, like this:[models]//normal=B747_400interior=B747_400_interiorI do this a lot for filming in FSX. However you're not really going to see any performance improvement by doing so. The external model is only being rendered if it's actually in view, and it mostly gets dumped from memory when you're in the VC. The external model is technically always in memory, simply because your aircraft's ground shadows are calculated from it, even if you're in the VC, but other than that it isn't causing any real performance hit.Similarly your VC is pretty much ditched from memory (except for gauge calculations) when you're flying from an outside view.If you fly in the VC all of the time, the only thing that can help your performance is a lower poly / lower texture vertex / simpler gauged VC. Also unlike the rest of the graphics in the sim, the 'entire' VC is being rendered all of the time that you're in it. This is so that things don't just 'pop' into view or appear untextured if you use a Track-ir or similar device and spin your view around. The sim has to provide for a worst possible case scenario here, and it's safer to have it all loaded and being rendered all the time, just in case the user suddenly decides to look at the floor, or behind them or whatever. Some parts of a VC can be hidden by a developer with visibility tags until certain parameters are met in the sim, but the angle and position of the camera aren't variables that such things can be easily based on in FSX.You could try converting as many of the VC's textures as you can to DXT1 format, which will improve performance, but you will probably hose bump and specular mapping if it's being used. Similarly you could reduce the size of the textures, which will again improve performance slightly, but you'll see a noticeable loss in quality from either.Long story short, try nuking the external model if you like, but I doubt you'll see any improvement at all. You could get the same effect by simply turning off your aircraft ground shadows setting. On really complex aircraft this can actually make a difference.At the very least though you can say you have wonder woman's jet in your hangar. ;)-mike

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Darned good answer!Put simply, there are two parts to most models: the cockpit and the rest of the aircraft. If you are in the cockpit, normally the rest of the aircraft is not rendered. If you are in any doubt, load up the default FSX LearJet, look out the door in the back and tell me what you see. Sometimes, the rest of the interior or even the entire aircraft is rendered, but this can cost you frame rate.Polygons don't have such a strong effect on frame rates as they used to, thanks to advances in graphics technology. In FS9, you had limits to how many polys you could use in a model, but in FSX, the number approaches infinity. Now the issue is vertices, which are the points where polys touch one another. Too many vertices, and you will create a model that bogs your system down.I don't think you can really look at a file size and judge the number of polys or vertices. The issue is algorythmic rather than arithmetic. The biggest thing that will cause an aircraft to perform poorly is probably textures. That's because the computer has to make several "passes" to display textures: one to set the proper colours, one to establish shadows, another to establish shininess (specularity), and so on. These passes are known as "shaders". The more shaders the texture requires, the more processing it will take to render them. on the other hand, shaders will create the subtle play of virtual light and shadow that makes a texture look realistic rather than rendered. Things have also gotten past the point where you could benefit in frame rate if there were fewer objects to be rendered onscreen. What I mean is say, 10-15 years ago, it was a common, ugly practise to make the cockpit view look like a tank slit, and to cover the screen with two-dimensional user interface. Back then, the less screen area that was devoted to 3D rendering, the better the frame rate. Or think of early MSFS, where your frame rates would jump because you were in thick clouds or fog. Since in FSX there is so much going on in the background, there are a lot of calculations being made for things you don't see. You can cut down on the number of calculations by lowering your detail sliders -- I'd say that's the most reliable and easiest tweak you can make.If you are looking to save on frame rates, turn down your traffic slider, turn down the water realism sliders, turn down terrain mesh complexity, and if you have to, lower the overall texture quality, or try flying in 16bit colour. Turn off bloom and any extra animations. Experiment with windowed versus full-screen mode. Jeff ShylukAssistant Managing EditorSenior Staff ReviewerAVSIM

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Another old FPS test is to view model from exterior but at an altitude/angle which doesn't include scenery or the horizon...You'll be amazed at how the FPS climbs when the scenery/horizon is not in view.As Jeff stated, FPS is the product of many factors and viewpoints:-)

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>Larry, is that pic in Nevada?>It's western Utah, on the way back from Nevada.L.Adamson

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>What a great idea! I never look at the outside view...>GeofaHi Geof,At the risk of being slightly off topic here i'd like to ask you this purely out of curiosity. I 'know' you for many years now here at avsim. Always find your posts very interesting mainly because you are a RW pilot ( especially loved your 'RW versus sim' comparison posts :-cool ).Regarding your comment that you never use spotview or any other 'outside' view mode in our beloved virtual flying world i just can't help being very curious about the reason why...In your RW flying experience you are obviously confined to the cockpit during flight, a flight simulator however gives you a chance to magically 'step outside' and admire the sight of your aircraft and surroundings from a point of view a RW pilot will never ever get the chance to do so.I mean, aren't you leaving one of the great opportunities that a flight simulator can bring you for granted this way ??....I could really understand your reasoning if you *weren't* a RW pilot too ( like the most of us here i presume... :-) )i.e keep it 'as real as it gets' but since you *are* why leave a lot of the advantages that a flight simulator can bring you, and flying a real aircraft can obviously not, out of picture and fly your virtual aircraft exactly as you would fly your RW aircraft ?...I mean(2), you obviously *must* love the looks of an aircraft, and especially your own ( that beautiful Bonanza, right ??... :-) ) too, right ?....Just curious, Geof, hope you don't mind... :-cool Cheers,Jan

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