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Help needed for ModelConverterX

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Help needed for ModelConverterX

Postby bigstones » Fri Apr 18, 2014 2:51 pm

Hello,
I'm using ModelConverterX to convert the models from an FS scenery with the permission of the owner, and planning to contribute to FG scenery only the GPL compatible parts. The axes seem to be messed, and what comes out looks in one (wrong) way in FG, and another (wrong) way in AC3D. So I asked for support on their forum, and Arno, the developer, asked me: "do you know how are axes in FG, so that I can check?"

I don't, so I'm asking you and will report back.

Note: for reference, there's also an older thread on their forum on this topic.

Note 2: I know there's a way to convert objects with fs2xplane -> blender, but with MCX there's this nice "batch converter" that can also convert BMP to PNG, and texture filenames to consistent uppercase (so that it works in Linux), without installing blender, setting up fs2xplane and messing with other scripts, going through a 3rd format and so on.

Note 3: I didn't try exhaustively, but I think MCX can work in Linux with WINE (not plain Mono).

Note 4 (lol, that's a lot of notes): I'll probably report soon some considerations on my experience in FS scenery conversion.
Last edited by bigstones on Sat Apr 19, 2014 10:53 am, edited 1 time in total.
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Re: Help needed for ModelConverterX

Postby Johan G » Fri Apr 18, 2014 7:39 pm

For the aircraft axis see the wiki article Howto:3D Aircraft Models.

It gets more logical if you consider that real life fuselage stations (i.e. distances from a datum point usually in front of the aircraft) usually increase towards the rear.
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Re: Help needed for ModelConverterX

Postby hvengel » Fri Apr 18, 2014 8:48 pm

For aircraft the selection of the "datum point" is typically something that is arbitrary and varies from manufacturer to manufacturer or for different designers. I have only looked at two actual sets of real aircraft blue prints in detail and one had the datum point located slightly behind the front edge of the cowl (North American Aviation) and the other had the datum point located at the front edge of the main spar (Stelio Frati) but I think it is also not un-common to place the datum point at the firewall. Since most FG models are based on 3rd party 3 views which seldom have the actual factory datum point marked many FG models place the datum point for the model at the nose of the aircraft so that all X offsets in the 3D model are negative numbers.
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Re: Help needed for ModelConverterX

Postby bigstones » Fri Apr 18, 2014 8:54 pm

Err, I think we're talking about world axes here, like "X points to south, Y points to east, Z points up".
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Re: Help needed for ModelConverterX

Postby VicMar » Sat Apr 19, 2014 8:33 am

Hi Bigstones,

I don't want to dampen your enthusiasm, but if you are using someone else's model you will need their permission to use it, and it must comply with GNU GPL if it is to be submitted to the scenery DB.

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Re: Help needed for ModelConverterX

Postby bigstones » Sat Apr 19, 2014 10:51 am

VicMar wrote in Sat Apr 19, 2014 8:33 am:I don't want to dampen your enthusiasm, but if you are using someone else's model you will need their permission to use it, and it must comply with GNU GPL if it is to be submitted to the scenery DB.

Hi, don't worry, I've discussed that already here (1st page). I'll add a notice to the first post here, to avoid misunderstandings for new users.
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Re: Help needed for ModelConverterX

Postby radi » Sat Apr 19, 2014 11:01 pm

First -- nice find! I wasn't aware of MCX, that certainly looks like a very convenient way to convert models, much better than my blender/fs2xplane/scripts hack. I'll update the wiki. I invite you to share your experience with MCX on a dedicated wiki page, that would be very useful.

Using a heading of 0 in the .stg file, I think the coordinate system is RHS with x pointing South, y pointing up, and z pointing West. At least this what I found is working for osm2city.

(BTW: To me, this is somewhat of a, well, non-intuitive choice -- anyone knows why they picked this system?)
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Re: Help needed for ModelConverterX

Postby Johan G » Sun Apr 20, 2014 8:52 pm

In addition to my theory above (and indeed I have seen the datum at the firewall a few times as well) I can imagine that it might have something to do with how three view drawings are laid out.

Doing a Google image search for "aircraft "three views"" one will find more aircraft with a left side view than a right side view, and thus the x axis maybe just happened to to be put towards the rear, and since the z axis would be up the y axis would be to the port side to form a RHS (right hand coordinate system, i.e. thumb, index and middle finger representing the x, y and z axis).

Pure speculation of course. :wink:
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Re: Help needed for ModelConverterX

Postby bigstones » Mon Apr 21, 2014 10:49 am

radi wrote in Sat Apr 19, 2014 11:01 pm:I invite you to share your experience with MCX on a dedicated wiki page, that would be very useful.

Using a heading of 0 in the .stg file, I think the coordinate system is RHS with x pointing South, y pointing up, and z pointing West. At least this what I found is working for osm2city

Thanks, that confirms an experiment I made. For the wiki, I'll consider it, luckily it would be a very short one, that tool is easy to work with. The problems come in when working with the converted models... I don't think that experience is wikificable, it would include a lot of swearing.
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Re: Help needed for ModelConverterX

Postby bigstones » Tue Apr 22, 2014 1:00 pm

radi wrote in Sat Apr 19, 2014 11:01 pm:I invite you to share your experience with MCX on a dedicated wiki page, that would be very useful.

http://wiki.flightgear.org/Howto:Conver ... ConverterX
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Re: Help needed for ModelConverterX

Postby radi » Tue Apr 22, 2014 10:14 pm

Thanks a lot!
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