[osg-users] Anomalies using VirtualPlanetBuilder

[Paul Brewster]

Thanks Jason,

I guess the geo info was lost when I rescaled the image.  I'll include 
another GTiff with the info in it.  The NODATA value is -32767, which is 
the smallest value possible, of course.  I don't know the exact value of 
the bad areas, but if you look closely, you can see craters on top of 
the "plateaus", so I don't know if it is purely a NODATA problem.

Thanks for the help.

Paul

Jason Beverage wrote:
> Hi Paul,
> 
> I tried to take a look at the sample file you created, but it doesn't 
> have any coordinate system attached to it so can't reproduce the 
> problems you were seeing with that data.
> 
> My gut feeling is that it has something to do with the handling of 
> NODATA values in osgTerrain.  What are the actual pixel values of the 
> file you are using where the spikes are occurring?
> 
> Thanks,
> 
> Jason
> 
> On Fri, Apr 4, 2008 at 10:29 AM, Paul Brewster <Paul.F.Brewster at nasa.gov 
> <mailto:Paul.F.Brewster at nasa.gov>> wrote:
> 
>     Hey all,
> 
>     I'm using VPB to build some terrains and have found a few anomalies
>     going on.  I have a single 10240x10240 DEM of part of the moon in a
>     16-bit unsigned format.  I can run gdalinfo and gdal_translate on it
>     just fine, so I will include a 2.5% version of the DEM so that you
>     can see
>     what I am talking about.  When I run "osgdem -l 1 --TERRAIN -d DEM.pds"
>     everything works really well, except I get some areas in the terrain
>     that just don't look right.  My nice round craters suddenly jump out
>     into plateaus in the middle.  It appears that somebody put some
>     monoliths in my moon craters.  Does anybody know what is happening here?
>        These anomalies are consistent throughout the levels, even if I
>     go all
>     the way down to full resolution.  At first I thought these might be from
>     signed/unsigned problems.  But as I look at the data, I'm not convinced
>     that is true.  Anybody have any ideas what is going on?  I'll include
>     some pictures to show what I mean.
> 
>     Thanks for your help.
> 
>     Paul Brewster
> 
>     Oh, and here is the vital information:
>     OpenSceneGraph: 2.3.5
>     VirtualPlanetBuilder: 0.9.6
>     GDAL: 1.5.0
>     OS: CentOS 4.5 (linux)
> 
>     The header to my DEM:
>     Driver: PDS/NASA Planetary Data System
>     Files: LDEM20723Sm.LBL
>     Size is 10240, 10240
>     Coordinate System is:
>     PROJCS["POLAR_STEREOGRAPHIC MOON",
>           GEOGCS["GCS_MOON",
>               DATUM["D_MOON",
>                   SPHEROID["MOON_polarRadius",1737400,0]],
>               PRIMEM["Reference_Meridian",0],
>               UNIT["degree",0.0174532925199433]],
>           PROJECTION["Polar_Stereographic"],
>           PARAMETER["latitude_of_origin",-90],
>           PARAMETER["central_meridian",0],
>           PARAMETER["scale_factor",1],
>           PARAMETER["false_easting",0],
>           PARAMETER["false_northing",0]]
>     Origin = (29.614999890327454,-29.614999890327454)
>     Pixel Size = (59.229999780654907,-59.229999780654907)
>     Corner Coordinates:
>     Upper Left  (  29.6149999, -29.6149999)
>     Lower Left  (      29.615, -606544.813)
>     Upper Right (  606544.813,     -29.615)
>     Lower Right (  606544.813, -606544.813)
>     Center      (  303287.214, -303287.214)
>     Band 1 Block=10240x1 Type=Int16, ColorInterp=Undefined
>         NoData Value=-32768
>         Offset: 1740000,   Scale:0.6
> 
> 
> 
> 
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