Jim Wilson
> It occurred to me that our 3-D modelers might not all be > running plib cvs. > Andy came up with an excellent improvement to the ac3d > loader/optimizer (new optimizer actually) that incorporates > logic to automatically split vertices in two so that they go > into seperate normal calculations (averages). Briefly, the > plib change gives us sharp edges automatically. > > For the many aircraft models this change really helps. But > for the models what were already designed to work around the > problems with the earlier plib, they end up looking a little > worse. I've gone through a few and for the most part they > have square or sharp leading edges on the wings now. > > I'm bringing this up now because this is the version of plib > that the next release of FlightGear will released for. > Looking at my own models, this has proven to be a very > difficult problem to deal with. > > Basically what you'll see is that a sharp edge is created > whenever the angle between the normals of adjacent surfaces > is greater than 46 degrees. Another way to describe the way > this works is that a cylinder object will appear round if it > has 8 or more sides. 7 sides will have sharp edges. > > This creates a serious problem for ac3d/blender modelers > because you will need at least 4 surfaces to make up a > leading edge. In practice you actually need 6 or more > because wing edges are not perfectly round. > > At some point simgear and plib will have to be modified to > support the ac3d 4 format or some similar scheme for setting > the angle. Either that or we'll finally be able to move to a > file format that actually supports normals "normally". > > For the time being though, I propose that we try to get this > default angle to a higher value. From my testing 61 degrees > seems to be a good number. 61 degrees means that a 6 sided > cylinder will be smoothed. Anything less (e.g. 4 or 5 sides) > will be sharp sided. Many of the aircraft models will still > need some modifications to recover their rounded shapes at 61 > degrees, but the process is much easier, with far fewer > vertices, etc. > > Best, > > Jim We seem to have jumped into something without really thinking it through. Pity. We need to implement something like the AC3D 'crease' sooner rather than later. Regards Vivian _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
