Howto:Place 3D objects with the UFO

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A very useful tool for placing objects within the scenery, created by Melchior Franz, is available with Flightgear 0.9.10 and later. It is an addon to the UFO aircraft which allows a user to place a new (or old) 3D object at any arbitrary location in the scenery with just a few clicks of the mouse.

Selecting the ufo

The first thing you need is a 3d model file to place in the scenery; let's say we'll use a catii-iii.xml object. You must save it in a path where this UFO feature can find it. The UFO searches the objects in the Flightgear/data/Models/ directory. In this example, we create a subdirectory called Tabu and save our catii-iii.xml there.

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Now start Flightgear, and choose UFO as your aircraft.

Placing objects

Once Flightgear has been started, fly with the UFO to the place you want the model to be positioned.

You must be sure about the size of the object in reference with the scene, it means: try to obtain the right value using some tools. Particulary, i recommend combine Googleearth and the rule tool and some size definition in the 3D software for obtain the right size, in my case, i have use Blender and the Caliper script. -- Alfonso de la Guarda

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Let's say we want to position the catii-iii.xml object at the end of a taxiway. We stop the UFO just above this intersection and press the space key, a Select Model window will open up where the contents of the Flightgear/data/Models/ directory will be shown. Select your model from this list, then close the window. The selected model path/name will be display in green text at the bottom left of the FlightGear screen.

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Now you may point the mouse on the scenery ground and left-click again, the CAT II/III ground marking model will be positioned there. Of course, it does not have the correct orientation and it's partly covered by the surrounding terrain, but we can adjust that.

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Rotating objects

Fly closer to the ground with the UFO, so that you can see it better.

Now press TAB (or Ctrl-I), and use the resulting sliders to adjust the latitude/longitude/elevation/heading of the model.

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Exporting the result

Now that the model is correctly positioned, press the D key to dump the model position data to the terminal. A few lines will be printed on the console, providing the necessary orientation data. You will save those coordinates into a scenery objects file in the next step. If you don't do that, next time you run Flightgear it will know nothing about the new object.

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In the terminal window, you get three sections printed out by the UFO with very detailed information about what's going on, we need the line at the end.

e000n50/e008n50/3089154.stg is the secenery object file where this object's coordinates have to be saved. The default place where to find e000n50 directory is inside Flightgear/data/Scenery/Objects/. You just open the 3089154.stg file with any text editor, add the following line and save it the file:

OBJECT_SHARED Models/Tabu/catii-iii.xml 8.57928135 50.03667992 105.9972 111.1

Now you have your object's position saved, and it will appear inside the scenery every time you start Flightgear.

Reload a saved session

If you press the E key while developing sceneries with Ufo, fgfs will generate an xml file with the dump of your current work, this file can be after reloaded giving the --config=path_to_file parameter. Example for Linux:

fgfs --config=$HOME/.fgfs/ufo-model-export.xml

Useful keys

See the UFO from the 'White Project' of the UNESCO page for ufo command keys.