On Tuesday 05 August 2003 00:12, Jim Wilson wrote: > "Curtis L. Olson" <[EMAIL PROTECTED]> said: > > > Lee Elliott writes: > > > I've noticed this effect too, on the 2d clouds. I think it's an ordering > > > issue. When I use transparent objects/textures in a model I have to be > > > careful of it's position in the object list - basically, every object that > > > comes after a transparent object is invisible when viewed through the > > > transparent object. With the 2d clouds it's as though they are coming after > > > the prop disk, in the object order, and so are invisible when seen through > > > it. > > > > I think we should be drawing the 3d model of the aircraft last, after > > the sky, terrain, and clouds. > > Actually the model objects are sorted so that the transparencies are last so > that they are higher on the stack and get rendered *first*. Blending requires > the foreground alpha object to be known first, which makes perfect sense if > you think about it. > > Someone might want to research the archives, on previous discussion of what > happens to the terrain and the model if you render the sky at a different point. > > Norm's idea may be the only solution that could eliminate the tradeoffs in the > current approach. One possibility might be to somehow tag transparent model > objects in xml (or ac3d object data) so that they can be moved after (or > during) a load. Then you could put the clouds into the transparent scenegraph > along with the transparent object parts, and everything else can go into the > other scenegraph. This would also be helpful to modelers who can at times > face complex difficulties with manually sorting objects. > > Yet another thing that suggests an writing ac3d loader customized for simgear. > > Best, > > Jim
It's a tricky one. If fgfs rendered the a/c after everything else it wouldn't work with the nice new clouds. I think there could be a problem with tagging transparent objects - most side/cabin windows on the large a/c are going to be done in the texture map via alpha/transparency against the hull paint scheme - not only is cutting out the individual windows a lot of work, it also tends to spoils the smoothing of the object, because of the uneven concentration of vertices, and also increases the poly count. Is an a/c model treated separately from the 'scene' or is it dissembled into it's component sub-objects, which are then z-buffered along with the rest of the scene polys? LeeE _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
