[osg-users] VTP height field issue

Christoph Ehrler ehrler-soft at gmx.de
Wed Sep 19 02:19:32 PDT 2007


Hi @ all,

probably it's a noob question...
I downloaded some data from NASA Blue Marble
(http://visibleearth.nasa.gov/view_set.php?categoryId=2355&p=3)
and tried to produce a whole earth representation with topography.

But the height field does not match the texture. North and South are
mixed up as well as East and West. But when I start mirroring and
flipping the height field JPG it does not resolve much.

Height field and texture are perfectly matching when using a normal
image viewer.
The problem is, if I use the height field as a texture the "mountains"
show up at a complete different location than they show up as "real
bumps" when using the same file as height map.



Height Field:
BMNG Raw Topography
srtm_ramp2.world.21600x10800.jpg

Texture:
Blue Marble Next Generation w/ Topography and Bathymetry
world.topo.bathy.200406.3x21600x10800.png


I converted both data sources with gdal_translate to TIF files and
added a image pyramid with gdaladdo but it didn't resolve anything.
I am building the paged database to single files (IVE) instead of
building to an archive (OSGA) but as I can remember it makes no
difference for this problem too.



gdal_translate srtm_ramp2.world.21600x10800.jpg srtm_ramp2.world.21600x10800.tif
gdaladdo -r average srtm_ramp2.world.21600x10800.tif 2 4 8 16 32

gdal_translate world.topo.bathy.200406.3x21600x10800.png
world.topo.bathy.200406.3x21600x10800.tif
gdaladdo -r average world.topo.bathy.200406.3x21600x10800.tif 2 4 8 16 32


osgdemd --whole-globe -d srtm_ramp2.world.21600x10800.jpg
--whole-globe -t world.topo.bathy.200406.3x21600x10800.tif -l 5 -v
1000 --geocentric -o blue_marble2.ive



Some suggestions welcome  :)
Thanks
Christoph



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