From: Alex P. <al...@fa...> - 2001-05-09 16:08:39
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> > I have no problem with people experimenting with various LOD schemes, > > but do be aware that this stuff is very hard, and I think you will > > find it harder than you think to ensure that the entire edge of the > > further tile is lower than the nearer tile, especially considering > > that we can view these things from any angle. > IMHO You are not right. Everytime you are looking from area with higher LOD > to area with lower LOD. Only when you look from height altitude down you can > see some discontinuity but not holes in terrain. There could help only > SmartMash :-) Actually, the case from above is easy, because the geographic edges of the tiles tend to line up pretty accurately. It's looking sideways that is bad. The pilot of an aircraft views the ground with an angle of between 0 and 5 degrees (aka 0 and 0.1 radians) and this heavily emphasises height errors. As Curt says, the problem is _hard_, both in simple software engineering to implement the code so it runs at reasonable speed, and in terms of the Computer Science to prove that the algorithm gives a reasonable answer, as well as in the algebra, to make the calculations always give an result with usable precision for all the degenerate cases. |