Oliver Eichler wrote: > > Just a small add on. Fabrice tried your patch and now he can grow rice in the > hills. Thus RasterIO will make staircases for interpolation. so I don't commit it to svn;). > > Oliver > >> On Saturday, 15. November 2008 20:53:42 [EMAIL PROTECTED] wrote: >>> Hi, Oliver >>> >>>>>> Another topic is to optimize the copy action of the elevation data. >>>>>> It's less a question of how to do it, more one of who is doing it. >>>>>> Either way, me or you, is ok for me. It's just important to assign it >>>>>> to one, to avoid double work. >>>>> I want investigate this task. I have some ideas and need make some >>>>> experiments. >>>> Ok, it's yours. I will ammuse myself with stacking raster, vector and >>>> DEM layers this weekend. Need to find a good concept for that. >>> I'm create first version of the optimization patch. It's draft only, but >>> reflect the main idea: "get elevation of all points and make one request >>> of RasterIO". >> Hi Andrew, >> >> just my 2 cents from looking over the patch: >> >> I would have done the API a bit different by passing a buffer to >> IMap::getElevation(). Of course you need some additional data like the >> buffer dimensions, topLeft, bottomRight and step size in meter for x and >> y. By that you can get the elevation matrix with one single call. And you >> can allocate the buffer on the stack instead on the heap with new/delete. I >> don't like new and delete on simple objects as this is prone to memory >> leaks. >> >> To let RasterIO do the interpolation might be a good idea. It will do it >> fast. But I don't think it does a good one. If you do an overzoom into a >> raster map you will notice that the pixels will get squares and these >> squares just get larger. That won't fit for elevation data. A 90m SRTM data >> will become like stairs on a 1m resolution map. The interpolation you >> disabled (float ele = w.c1 * e[0] + w.c2 * e[1] + w.c3 * e[2] + w.c4 * >> e[3];) will do better. >> >> But maybe RasterIO recognize the special character of the DEM data and >> applies a better interpolation. It's worth a try. >> >> Just for the records: Contour shading does quite the same. It just does not >> look as staircasey because the array is smoothed by a lowpass filter. But >> it would have been too bad to derive the elevation value from it. That is >> why I made this 4 point interpolation. Once we can interpolate a whole >> region fast, I will use it for shading. That should make much better >> results. >> >> I can't apply the patch locally as my source tree is on hiatus for Garmin >> typ file implementation. But I will try after that. >> >> Oliver >> >> >> >> >> >> >> >> ------------------------------------------------------------------------- >> This SF.Net email is sponsored by the Moblin Your Move Developer's >> challenge Build the coolest Linux based applications with Moblin SDK & win >> great prizes Grand prize is a trip for two to an Open Source event anywhere >> in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ >> _______________________________________________ >> QLandkarte-users mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/qlandkarte-users > > > > ------------------------------------------------------------------------- > This SF.Net email is sponsored by the Moblin Your Move Developer's challenge > Build the coolest Linux based applications with Moblin SDK & win great prizes > Grand prize is a trip for two to an Open Source event anywhere in the world > http://moblin-contest.org/redirect.php?banner_id=100&url=/ > _______________________________________________ > QLandkarte-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/qlandkarte-users
------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ QLandkarte-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/qlandkarte-users
