I've used Celestia before, and from what I can tell... Much like "Microsoft Flight Simulator", there are models for different ports (in this case, spaceports rather than airports). When you are near the ports, the level of detail for those ports are increased. When you are further from them, however, they use simpler and simpler models, until eventually, they don't need to use models at all, and can resort to bumpmapping, normalmapping, and eventually you're so far away, you can just ignore the fact that the port exists in your frame of reference. It is the same thing with planets and moons, in fact, and stars themselves. Obviously, scale plays a big part, and Celestia interrelates that with your distance from the object, providing a reasonable facsimilie of real-life effects.
At least, that's my take on it. I'm not sure how coordinate systems interplay in all of this, but in Celestia, you have frames of reference, oriented toward your target object. You are told what your altitude is (your distance from the target object), and your orientation in regards to said object. That's what I could figure out, but I'm still not quite sure how to program it all to fit on a floppy. -Steve On 2/1/07, chris <[EMAIL PROTECTED]> wrote: > it uses a combo of very high precision and local frames of reference > (which eventually translates to moving the origin piecewise). > "A position-object contains the exact coordinates of a point in space. > Internally position-objects use 128bit per component and therefore > have higher precision than available directly in Lua (which typically > uses 64-bit double-precision). A position is relative to a coordinate > system (i.e. a frame of reference, see frame) and may need to be > converted to or from universal coordinates before further use." > Sounds like one of the three main categories of approaches to avoiding > spatial jitter: piecewise shifting of origin in a continuous space. > That is a good model and what I see as a first stage solution towards > a full origin centric approach. > FYI Michael Jones (Google Earth CTO) once said to me in a Cartographic > birds of feathers meeting at siggraph that he used something like a > floating origin concept (which I was presenting at the time) on Google > Earth. > > chris _______________________________________________ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
