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.
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
