Hi Christope, I've doing a clean out of old submissions, and this one from back in July last year I have done reviewed and tested against the model you suggested and found that it didn't fix things completely - I still saw artefacts. ]
I tried build the database using --terrain to select a osgTerrain::TerrainTile based database and this cures the artefact. --terrain will soon be the default, so I wonder if about whether this issue is still critical or not. Cheers, Robert. On Fri, Jul 18, 2008 at 12:42 PM, christophe loustaunau < [email protected]> wrote: > Hi, > > I have found a little problem with some normals in VPB. > If you generate a terrain with two dem files : global.tif , local.tif > -->local.tif have a better resolution than global.tif. > -->local.tif is part of global.tif > In other words imagine global.tif representing the USA and local.tif New > York. > > If you generate the terrain with this command line : > vpbmaster -d global.tif -d local.tif --geocentric -o terrain.ive > > You can see in the generated terrain that some normals are wrong, see > screen.png. > > I have searched the code for this bug, and I have found that in both > functions > equalizeCorner() and createPolygonal() (in destination.cpp) there is a > problem if there are two corners that have different resolutions. > The vec2 heightDelta computed in equalizeCorner() is the average of the of > all the corners's heightDelta. When dealing with 4 tiles, if three corners > have the same resolution, they may have all a heightDelta that is nearly the > same, but the fourth corner with a different resolution has a really > different heightDelta (generally smaller as it's more precise). These > heightDelta are then used in createPolygonal() to compute the normals. The > small heightDelta* *results in a bad calculation of the normal. > > I have found a solution but I'm not sure if it's the best one...In fact, I > checked in equalizeCorner() if the corners have different resolutions, if > it's the case, I change the normals only for those who have the lowest > resolution. > > Anyways, here is a patch based on the svn version. Tell me what you think > of it and let me know if you find a better solution. > > I have joined to the mail global.tif and local.tif if you want to reproduce > the problem (the two images are very little, so it's very quick to generate > the database). > > Regards. > -- > Christophe Loustaunau. > > _______________________________________________ > osg-submissions mailing list > [email protected] > > http://lists.openscenegraph.org/listinfo.cgi/osg-submissions-openscenegraph.org > >
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