On Tuesday, December 11, 2012 15:51:06 Christian Schmitt wrote: > Hi Adrian, > > generally, yes a LOD system would be nice, but it would need considerable > changes on the btg format or a switch to something new. > I'm currently investigating how to make elevation calculation for the > terrain easier and more versatile. I want to use gdalchop for general > processing as gdal reads almost all kinds of raster formats. So we would no > longer have to rely on hgtchop, srtmchop and demchop (yes, it's mad). > Also, depending on what is possible, i would like to get rid of terrafit. > We have great SRTM data, reduce the amount of points and then have to > interpolate like mad when we need the elevation of a certain point. GDAL > has interpolation routines included (beyond linear interpolation) and I'd > like to make use of that. I noticed yesterday, that there is already > gdallocationinfo which reads the elevation on the fly for a given lat/lon. > This might be worth investigating. > > Cheers > Chris
Hi Chris, You are correct about SRTM and GDAL, but I'd like to add that my greatest problem now is not reading the elevation (this is already done, albeit innacurately), but reading and placing the material information in the same table as the elevaton info. And this I can currently do only by using polygon output from ogr-decode. Also, I'm relying on text files generated by terrafit, because I have a simple python script to get that into the database. I'll see how to adapt in the future. The wonders of using sqlite is that you can attach and detach on the fly databases to the main connection, and if you have unique tables, the amount of code needed is really small to handle transition from one area to another. I already have elevation sampling working in Flightgear with 10x10 degree tiles (for whatever distance that allows), the very nasty trick is obtaining that material information for each point and I'm currently working on a fast method to get that info. Right now I take polygons as generated by ogr-decode, and apply the GEOS routine Within test for each elevation point. Considering 12,000,000 elevation points for a 10x10 tile, and lots of polygons generated by ogr-decode, it's literally taking days or weeks to complete this. I will dedicate some time in the future to think about terrain LOD without significant changes to the BTG format. The current system is definetly inferior to most every other simulator out there. Cheers, Adrian ------------------------------------------------------------------------------ LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial Remotely access PCs and mobile devices and provide instant support Improve your efficiency, and focus on delivering more value-add services Discover what IT Professionals Know. Rescue delivers http://p.sf.net/sfu/logmein_12329d2d _______________________________________________ Flightgear-scenery mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/flightgear-scenery
