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Walking through the Scenery: The portable Walker

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Re: Walking through the Scenery: The portable Walker

Postby Gijs » Fri Jun 27, 2014 7:55 am

There is a Config field in FGRun under Advanced > General.
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Re: Walking through the Scenery: The portable Walker

Postby chriscalef » Fri Jun 27, 2014 3:36 pm

Ah, thanks everybody, that's much better!

Somebody (DFaber?) should probably fix the instructions on the download page though, it currently directs users to use Advanced->Properties.
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Re: Walking through the Scenery: The portable Walker

Postby chriscalef » Fri Jun 27, 2014 5:18 pm

Sooo... I probably shouldn't even say anything at this point, given that I have no idea if I'll have enough spare time for it anywhere between now and next winter, but for purposes of getting feedback I guess I'll go ahead and bring it up.

First off, I *love* the fact that flightgear's community has motivated to the point of getting a person out of the plane! (Are there any flight sims on the market even now that let you do that?) This is truly awesome.

However, my particular specialty for the past several years has been human animation, or specifically writing a tool to facilitate working with animations (see my beta product here, it is still under development and lacks much in the way of docs and examples, but it does basically work: http://www.ecstasymotion.com)

What occurs to me on initial assessment of the walker is that we appear to be using hand edited xml files to generate all the motion (unless there is a gui tool somebody is using to generate that xml?)

Being a coder who has no real talent or inclination to generate animations by hand, I've spent a number of years working instead toward first being able to import anims from motion capture, primarily in BVH format, and later toward importing and exporting FBX files, for use in Unity and other game engines. My app also applies ragdoll physics using the PhysX API and a certain amount of hand rolled AI involving behavior trees and scripted scene events.

My initial observation, then, for how to open up the walker to the wide, wide world of existing animation libraries, instead of hand rolling all of our anims in house, would therefore tend to go in one or both of two directions:

One, write a BVH converter to produce standard flightgear/walker XML animation files from a source BVH. Check out sources like the free Carnegie Mellon BVH Motion Capture Library (http://mocap.cs.cmu.edu/) to get an idea of the number of anims we would then have available... This would be the least invasive option in terms of what already exists, in that it would not require changing anything at all in the current setup. However, it would be a significant amount of labor. I have done this before and am 100% confident I could do it again, but not absolutely certain *when* I might sit down to do it again... This option would also leave us with the current walker models, which while far superior to anything I myself could put together in a modeling program, are also a little bit behind the times if I may say so, in terms of expected first person experience in 2014.

The second option would be to open up a giant can of worms and fire up the FBX support already contained in OSG. I do not know if there are licensing purity issues with using FBX in FlightGear, or if the bloat would be intolerable, but some here may remember that I actually did already make an inroad in this direction last year:

viewtopic.php?f=18&t=19250&p=178440&hilit=fbx#p178369

I had some problems with the texture import, as you can see, and I never tried to get an animation running, but I gave it all of a day or two to get to the initial point you see there and then moved on to other things. In the end, FBX support could be anywhere from very easy to very difficult, but it would certainly open up a world of advanced human models far beyond our little collection here, and it would also allow animation imports (especially if anyone wants to buy my app and use it to export FBX from BVH inputs, after doing editing and physics, *cough*, very sorry it only works on windows at the moment though).

I have no idea how difficult it would be to modify the existing walker code to work with an FBX model and play FBX anims, however. A side benefit of FBX, though, is that you can also have whole scenes with many characters, plus even lights, etc. contained in one FBX file, which could allow things like complex airport traffic, dudes running around with carts of luggage, pedestrians, etc. all contained in one file and played at the airport when you come within a certain range...

Anyway, like I said, I'm going to have a busy summer and a lot of this is somewhat idle speculation on my part, but I'm also becoming increasingly interested in using flightgear for my own nefarious schemes, so I may surprise myself and find time sooner than I think. Would be very interested in feedback from the community.

EDIT: oh yeah, in rereading that FBX post above, I rediscovered this link which already contains much feedback and discussion on this subject - viewtopic.php?p=178059 - going back to read that again.
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Re: Walking through the Scenery: The portable Walker

Postby chriscalef » Fri Jun 27, 2014 5:38 pm

Hm, in that discussion Buccaroo states:

"I wish .FBX wasn't in the clutches of @#$% Autodesk. Course I also wish I had my own starship."

I know that FBX is a proprietary format, and please forgive my ignorance here for a second, but does that mean it is strictly off limits for a project released under GPL to use it at all? And is there a difference between including support for it in the main flightgear project as compared to me having my own fork of flightgear that uses FBX? I know there could be bloat issues and implementation difficulties as well, but thinking just of the legal framework at the moment.
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Re: Walking through the Scenery: The portable Walker

Postby Hooray » Fri Jun 27, 2014 6:54 pm

I don't know, it's obviously up to you what you do locally - but just look at FG and its current state, there are quite a few technologies that would have proprietary equivalents, and the fact that FG doesn't use those is a good thing for the project and the whole community, even despite tailored & excellent tool chains (in comparison to our "generic" tools like Blender3D/QGIS/GRASS etc).
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Re: Walking through the Scenery: The portable Walker

Postby psadro_gm » Fri Jun 27, 2014 7:04 pm

FBX format is proprietary - they have an 'open source' sdk which is not compatible with the GPL.
The blender devs have been working on binary support - you can read about their troubles / status here: http://code.blender.org/index.php/2013/ ... ification/
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Re: Walking through the Scenery: The portable Walker

Postby chriscalef » Fri Jun 27, 2014 10:13 pm

Ah, right, one of the comments on that link I believe answers my question...

"Please consider using FBX SDK. You will always be behind regarding new versions and features otherwise, and it would be much easier with the SDK. License is no problem if you have fbx code in its own process, and IPC makes it slower but not much."

Which I take to mean that, while of course I can do whatever I want locally, but if, theoretically, I had an interest in starting a FlightGear based project which made direct use of the FBX SDK, and wanted to share it with others, I would be in violation of the GPL. So in order to overcome this obstacle I would have to create a whole separate importer/exporter process and convert the models into ac or some other open format before I would be legally safe to use them in any derivative of FlightGear?

Not laying out a plan here, just trying to wrap my head around the legalities.
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Re: Walking through the Scenery: The portable Walker

Postby chriscalef » Sat Jun 28, 2014 5:12 am

Further research reminds me that Autodesk's FBX SDK also imports and exports a number of formats on its own, so a standalone app could actually be an extremely simple affair if their converters actually work. They supposedly save to collada, obj, and 3ds. I guess obj is probably the lightest, if it supports all the required features, but theoretically any of those could be used with the appropriate plugins for OSG.

There would of course still be the technical issues of integrating an advanced modeling/animation format into flightgear's current way of doing things, and many users may not care very much about this feature, but I for one certainly would like to have it! As much for animation of ground characters as for the pilot's own out-of-airplane experience.

Will have to poke around a bit and find what was done before regarding 3ds or obj in flightgear...
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Re: Walking through the Scenery: The portable Walker

Postby Hooray » Sat Jun 28, 2014 10:27 am

yes, separate process/IPC are the "standard" methods to circumvent the GPL that are also in use by various FG systems, implemented by contributors who did contract work that couldn't be contributed back.
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Re: Walking through the Scenery: The portable Walker

Postby chriscalef » Sun Jun 29, 2014 2:46 am

Okay, so, I think I now have a plan. It will probably take a while before I can break away enough time to do it, unfortunately.

My Goal: to get a more advanced 3D model format than .ac working in flightgear, supporting at least the features of: 1) skeleton-based vertex morphing, and 2) animation, as part of the format.

Formats under consideration: obj, 3ds, dae (because these are supposedly directly exported by the FBX SDK, and are also to the best of my knowledge GPL friendly)

Methodology: Since FBX SDK is off the table for direct inclusion into FlightGear because of GPL restrictions, making a separate process necessary; and since my app Ecstasy Motion would also benefit from supporting more formats, and is already using the FBX SDK; I propose to test all of the above mentioned export formats in the FBX SDK instance in EM and see if any of them work - including textures, vertex morphing, and animations. I should be able to test the results on other apps (like blender) before trying to bring them into flightgear, but ultimately will want to add the appropriate OSG plugins and test them if FG.

Note that this immediate goal does *not* cover supporting existing features for aircraft models, like calling aileron and elevator animations - for now I'd be satisfied to be able to call animations on ground entities only and see them work in flightgear. More involved support would certainly worthy of discussion but not my current top priority.
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Re: Walking through the Scenery: The portable Walker

Postby Hooray » Sun Jun 29, 2014 10:04 am

chriscalef wrote in Sun Jun 29, 2014 2:46 am:Note that this immediate goal does *not* cover supporting existing features for aircraft models, like calling aileron and elevator animations - for now I'd be satisfied to be able to call animations on ground entities only and see them work in flightgear. More involved support would certainly worthy of discussion but not my current top priority.


Usually, such things will be scripted via "Nasal", i.e. there are properties for animations that are really just handled by some Nasal-based listener/timer that modifies the properties, e.g. by running some interpolation/extrapolation and filters and updating the corresponding properties. So called "Property Rules" might be another option that should be less GC-sensitive.
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Re: Walking through the Scenery: The portable Walker

Postby chriscalef » Sun Jun 29, 2014 10:08 pm

Ah, and more research turns up the fact that obj format doesn't support animation at all, so I guess it's down to 3ds or Collada.
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Re: Walking through the Scenery: The portable Walker

Postby chriscalef » Tue Jul 08, 2014 6:19 am

Well, some more research returns interesting if somewhat disappointing results. First off, unless I'm simply calling it wrong (which seems likely, but haven't gotten any response yet to my query on their forums and haven't figured out any better way to do it) the FBX SDK seems unwilling to export any file that isn't some version of fbx. This is very odd and seems very likely to be user error on my part. However, so far, nothing I've tried has resulted in an export that isn't some version of fbx, sometimes ascii, sometimes binary, but never dae or 3ds as I was under the impression I should be getting.

However, while I'd really like to be able to use FBX's supposed export capabilities to broaden the reach of my app, for now I'd really just like to see if I could take the export of my app, in fbx, and by hook or crook at least manage to convert it to a format legally usable in flightgear. Toward that end, I turned back to the standard Autodesk Fbx Converter utility program (http://usa.autodesk.com/adsk/servlet/pc ... d=20481519).

With that, I am able to load my fbx files and successfully convert them to any other version of fbx plus dxf, obj, and collada. Support for 3ds, it turns out, was dropped by Autodesk in 2011, so if I want a format with full support for skeletal animation it seems that collada is the only option left on the table.

However, the good news is that at least on cursory visual inspection, the fbx converter appears to be making a successful 1.4.1 collada file. The bad news for me is that so far every one of the free (or otherwise available to me) collada viewers I have tried to use so far have run into errors and failed to load this collada file. Blender was closest, in that it loaded the skeleton and was able to play the anim, but it had no mesh. Torque and Sketchup appeared to load the file but showed nothing. A couple of other free viewers also failed to deliver. However, the primary test will be to see if OSG in flightgear will be able to render the model, and for that I need to get my whole project back in working order on my new OS, so it might be a few days.
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Re: Walking through the Scenery: The portable Walker

Postby philnx » Fri Jul 11, 2014 2:39 pm

Hello everyone,

I appreciate the effort that some of you are putting into the new "Walker" feature, as it shows to the world (among other notable things) that FG is a true open project. However, I'm one of those FG "pilots" who use this software as a more traditional flight simulator, and don't intend to switch to a kind of "3D social gaming" mode (though I'm sometimes active in MP in order to have some "real traffic" around, and to generate some myself). That said, will the "Walker" feature be enabled by default, thus possibly making the whole software more resource-intensive, or will it be implemented as an option, like several other FG features?

Please don't get me wrong: this is not a criticism, and I don't want (not even remotely) to start a flame war between different "philosophies" related to FG development.

Any light that anyone will shed on this will be much appreciated.

Happy flying,
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Re: Walking through the Scenery: The portable Walker

Postby Johan G » Sun Jul 13, 2014 6:55 pm

For the most part I agree, though it could potentially be used for pre- and postflight walkarounds. ;)
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