How about we leave a hole in the terrain, where the VASI is located, and put red and white bright surfaces underground ?
> Christian, > > It appears that in opengl, environment mapping is based on the the > view direction relative to the object normal, not the eyepoint > position relative to the object normal. > > In otherwords take an outdoor scene where our view is upright (i.e. up > is opposite of gravity). There is a small reflective sphere at our > eye level some distance away. We are looking directly at it so it is > drawn in the center of our screen. We should see a reflection where > the top half of the sphere shows sky and the bottom half of the sphere > shows ground. > > Now if we pitch our view 30 degrees down, but keep the sphere in view, > we would hope that the reflection wouldn't change because our eyepoint > hasn't moved so we should see the same reflection. However, opengl > environment mapping is a crude approximation and it only cares about > your view "direction" so now the reflection is drawn as if we were > viewing the sphere from a 30 degree up relative view position. > > This means if we try to use environment mapping to impliment VASI/PAPI > type lights, they will only react to our view direction (i.e. amount > of pitch up/down and heading) not our actual position relative to the > glide slope (i.e. we are a little high, little low, etc. on our > approach path.) > > So my conclusion is that we will need to find some sort of fancier > opengl "trick" or else we will have to resort to implimenting > vasi/papi lights "the hard way." > > Cub mapping *seems* like it might do the trick, but it's unclear to me > at this point how we would get the cub map space to align properly > with the flightgear world. > > In spherical environment mapping, "up" in the environment map texture > always corresponds to the current view up so if you do a 180 degree > roll and look at the same object, the reflection will now be > backwards. I don't know how this is handled with cub environment > mapping. > > Regards, > > Curt. > > > Christian Mayer writes: > > "Curtis L. Olson" wrote: > > > > > > Here's a question I'll throw out to the list on my way to bed. > > > > > > I'm working on VASI/PAPI type lights tonight and am running into a > > > problem. I'm using environment mapping with the normal aligned along > > > the desired approach path. This almost works as expected except for > > > one major problem. The texture coordinate that is generated is > > > ***highly*** dependent on the object's position on the screen. > > > > > > Thus, on approach, simply pitching up or down radically changes the > > > color of the vasi light, even though the relative view position > > > changes very little. > > > > Something to take cara about with environment mapping is the orientation > > of the normal vector. If you've got it wron (i.e. pointing away from you > > not towards you) you'll see the singularity - and thus quite possibly > > rapid changes. > > > > Apart fro mthat I can't help - except to point you to the little demo I > > wrote quite a long time ago. It seemed to work correctly for me. > > > > CU, > > Christian > > > > -- > > The idea is to die young as late as possible. -- Ashley Montague > > > > _______________________________________________ > > Flightgear-devel mailing list > > [EMAIL PROTECTED] > > http://mail.flightgear.org/mailman/listinfo/flightgear-devel > > -- > 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 > > _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
