FlightGear - LODLOD = Level Of Details.Rendering high detailed objects with FlightGear can be a disaster; too much details means too much 3d objects to be rendered, that takes a lot of work for the CPU and the graphic card. You can get very nice visual results but very low fps when the scenery is full with high detailed 3d objects. The solution is based on displaying high detailed objects when they are not too far from the point of view only, and rendering lower detailed versions of the same objects when the point of view is far distant from them, i.e. when the details are not visible anyway. FlightGear provides three LOD whose default values are (in meters): /sim/rendering/static-lod/detailed = 1500 /sim/rendering/static-lod/rough = 9000 /sim/rendering/static-lod/bare = 30000 We can modell three versions of the same 3d object with different level of details and let FlightGear display them one at a time, regarding LOD values. An easy way to implement this technique is to create an object.ac file with those three versions of the modell inside, and name them "high-detail", "rough-detail" and "bare-detail". We then create a simple object.xml, which makes use of the "range" animation, like this. This object.xml file tells FlightGear to use the object.ac file, to display the "high-detail" object inside object.ac when the point of view distance from the object itself is between 0 and /sim/rendering/static-lod/detailed meters, to display the "rough-detail" object inside object.ac when the point of view distance from the object itself is between /sim/rendering/static-lod/detailed and /sim/rendering/static-lod/rough meters, and so on. Finally, FlightGear will not display anything when the distance is more then /sim/rendering/static-lod/bare meters. Of course, you have to triple your 3d modelling work in order to get all those versions, and you get a more complicated scenario when the object.ac file contains many different objects inside, each with a unique name and properties, but that's just an evolution of the base scenario. Keep in mind that building high detailed objects gets some really nice visual results and pleases every user, but you will get a tremendous drop in frame rate when those details become too much, and the best way to avoid that is to not let Flightgear render what a user cannot perceive, i.e. useless detailed object from a distance. Roberto |