Thanks for the reply Robert. When you mention default size I assume you are referring to the 63x63 pixel resolution that I mentioned? Is that the default size for a tile? I did a grep on the entire VPB src package for "63" and didn't find anything related to default size values; am I misinterpreting you?
You may be right about VPB not being the optimal solution for my needs, but I am very hesitant to try to start from scratch because I am making extensive use of the fact that osgdem creates a geocentric database that i am able to place objects onto using lat-lon coordinates. I also wouldn't know where to begin when it comes to interpreting dted data in C++ and creating a geocentric database. When you say that I might want to generate geometries and textures myself do you mean writing all of that logic from scratch or did you have other osg utilities in mind? I could also try to start from VPB src and modify osgdem to create double-triangle-pixels according to the number of pixels in the source geotiff file but i don't know how straight-forward that would be. I'm not looking for extensive help or anything but if I could at least know what a good starting point would be to sink my teeth into I would be much better off. Thanks again, -Ethan robertosfield wrote: > Hi Ethan, > > VPB is built around the idea of creating large paged database, scaling > up to terrabytes in size, rather than single tiles, and render the > terrains at a solid 60Hz. These requirements mean that one has to > tile and LOD the terrain, which is where the default size you are > seeing is coming in. You can change the default size is you want but > typically you wouldn't want to increase it as this will impact > performance. > > For you needs it may well be that just creating a geometry and texture > directly rather than using VPB would be appropriate. > > Robert. > > On 17 November 2011 16:13, Ethan Fahy <> wrote: > > > Hello all, > > > > I start with dted data and use gdal_translate to convert this data to a > > geotiff. This geotiff has 278x305 pixels. The lat-lon bounding box has > > right angles in lat-lon space, but due to the mercator projection being > > used, the geotiff has some no-data areas along the edges. > > > > I then run osgdem using the following command: > > > > osgdem --geocentric -d elevation.tif -l 1 -o elevation.osg --POLYGONAL > > > > When I view this elevation.osg file in wireframe I see that the primitives > > that make up the terrain are large if there is a small elevation gradient > > and small if there is a large elevtion gradient. This makes sense; it's > > only using as much detail as needed. For my purposes, I want a set of > > primitives that is in the same grid as the original pixel map. So, I > > repeat the osgdem command above but add the --no-terrain-simplification > > flag. When I look at this osg file in wireframe, I see that it has created > > a 63x63 pixel terrain, with each pixel made up of two triangles. There is > > also a second primitiveset that is simply a quadstrip that wraps around the > > edge of my terrain. This is close to what I want, but my questions is this: > > > > Why is the osg terrain 63x63 when the source geotiff was 278x305? What > > process is osgdem using to determine how many of these two-triangle-pixels > > to put in each direction in the output product? Do I have any control over > > these parameters without modifying the osgdem src? I've looked at all the > > osgdem flags and nothing jumped out at me. > > > > Thanks so much for any help you can give me. > > > > ------------------ > > Read this topic online here: > > http://forum.openscenegraph.org/viewtopic.php?p=43931#43931 > > > > > > > > > > > > _______________________________________________ > > osg-users mailing list > > > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > > _______________________________________________ > osg-users mailing list > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > ------------------ > Post generated by Mail2Forum ------------------ Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=44120#44120 _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
