Hi Curt,
On Saturday 26 May 2007, Curtis Olson wrote:
> If this works as well as advertised (and it appears to) then this is a
> really nice feature of OSG. Dealing with whole earth scales using floating
> point numbers requires a few non-obvious tricks. For those not familiar
> with the issue, a floating point number can represent about 7(-8?)
> significant digits. The est-epsilon program in the tests directory of the
> FlightGear source estimates the smallest floating point number that can be
> represented.
>
> In practical terms, this means you run out of floating point precision
> trying to accurately place yourself or objects on the surface of the world.
> You could easily a several meter shift in the position of objects (or the
> view point) depending on whether or not the results of your placement math
> gets rounded up or rounded down.
>
> You can just use doubles because *everything* that opengl does uses
> floating point math.
>
> This leads to scenery that will jitter back and forth by this amount as you
> move. It's a huge problem for flight simulators, unless you are studying
> alchohol effects on pilots or something. :-)
>
> OSG appears to have come up with a nice workaround/solution to the problem.
> Cool ...
Yes, this works in that way. You can already see that in fg HEAD.
Robert's library is heavily used in the Viz-Sim industry and thus exactly
written for our needs :)
Greetings
Mathias
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