David Megginson writes: > Norman Vine writes: > > > but IMHO what is needed are "imposter tiles" > > > > "imposters" are where you use a 'texture only" substitute > > for the geometry that are computed on the fly 'often enough' > > This is 'radical' LOD but in our case the tiles out on the > > boundary are really just 'little slivers' and there is no need for > > anyting else. I would think that we could easily lump many > > tiles together into these impostors to form a 2 level ring of > > 'near' and 'far' "impostors" around our current scenery. > > Yes, I think that's a very good idea; in fact, if you wanted to go to > three layers, the furthest one could be simply untextured, coloured > polys (that's what you'd see from 120,000ft, for example). For each > tile, we need to sample to find the commonest material and then use it > for the texture (and/or colour) at load-time.
One thing we'd need to think about before we got too far down this path is the texture RAM requirements of such a scheme. > Curt is worried about joining meshed tiles (with irregular terrain) to > flat tiles, but I don't think that will be a big problem if the flat > ones are far enough away. If we wanted to, we could also sample the > elevation variation for each tile to help us decide how far away it > should be drawn as a full mesh: flat tiles could go to a single poly > much earlier than mountainous ones, for example. It will be a problem. If you don't account for even the tiniest gaps between tiles, they can show up as a whole line of pixels no matter how far away. If you are then trying to match complex terrain in one tile to a flat rectangle being the next tile, this problem will only get worse. These pixel wide gaps glimmer and shimmer and change every frame drawing undue attention to themselves. We would need to do something like put 'long enough' skirts around all the tiles (including the ones with terrain mesh) to hide the gaps. This could certainly be done though and is something I've begun to look at for airport areas. Curt. -- Curtis Olson IVLab / HumanFIRST Program FlightGear Project Twin Cities [EMAIL PROTECTED] [EMAIL PROTECTED] Minnesota http://www.menet.umn.edu/~curt http://www.flightgear.org _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
