[osg-tds] osgTDS with coordinatesystemnode and large geocentric Databases

Sat May 23 07:01:34 PDT 2009

Hi Don,

Ok, regarding osgEarth I got it, so lets refocus only on osgTDS.

My scene graph logic is a CoordinateSystemNode as root node, and as childs my geocentric earthmodel  and my other models.

But for easier learning a used a simple setup with the standart osgviewer program, just to verify that osgTDS works with databases generated by VirtualPlanetBuilder.

I have a flat database which I generated with VirtualPlanetBuilder. (The Puget example dataset)

Additional I use the house.osg from the osgTDS examples. I modified the transform matrix at the beginning of the house.osg file, so the house appears not on the corner of my scene, but inside my scene. Translation works because the house is visible in my scene. I suppose it is far enough away from the edges.

Now there is no warning like I mentioned below, but on the other hand there is also no terrain modification, as if osgTDS wouldn’t be there.

The debug-Messages at OSG_NOTIFY_LEVEL = INFO tells me he is triangulating something, but I can’t see any effects.. 

Du you have an idea what could be the problem?

Thank you for your help,

Torben

Von: burns.don at gmail.com [mailto:burns.don at gmail.com] Im Auftrag von Don Burns
Gesendet: Freitag, 22. Mai 2009 18:44
An: Torben Dannhauer
Cc: osg-tds at andesengineering.com
Betreff: Re: [osg-tds] osgTDS with coordinatesystemnode and large geocentric Databases

Hi Torben,

On Fri, May 22, 2009 at 7:39 AM, Torben Dannhauer <torben at dannhauer.info> wrote:

Hello,

I discovered osgTDS for terrain modification and have some trouble to get it working.

I got the source, compiled it and integrated the files into my OSG installation.

osgTDS with the example data works great and has an impressive output.

Unfortunalety osgTDS seems not to work with my geocentric database (WGS84) which I build with VirtualPlanetBuilder.

During the application startup a message is displayed, that the model is not or not completely over Terrain:  “Terrain Deformation Software:  ERROR in Target Database Base definition:  at least one target is not completely over terrain.”

SO you understand the historical implications, VPB is a newer product than osgTDS, and osgTDS has not been kept up with advances in osg, which would explain the difficulty you've had with integration.  osgTDS is a community supported project by design, so your work with it could be valuable in keeping it up to snuff.

The message you are getting is undoubtedly (I haven't looked at the code for about two years), the result of your models being in a different coordinate space than the terrain over which they are positioned.  I would guess that the solution is to use the same sort of coordinate node provided by OSG to position your models.

There may be another consideration, in that osgTDS makes some assumptions about "which way is up", or more specifically, "which is the bottom of the models", and may require some transformations to get things right.... (I'm not sure here, just guessing).

I have read the Documentation but there are still some beginner questions:

1.       The osgTDS loader seems to load all targets mentioned in the .tds file by himself. Is it possible to relocate this models in my scenery to their right place and the terrain will always be corrected the right way?

I believe that we are on the same page here regarding my first paragraph.  You probably need to group your models under a coordinate system node.  However, you may also need to build the support for the coordinate system node into the osgTDS traversers, as this node did not exist when osgTDS was written. 

2.       How is the loading logic build? Which model/target is parent/child of which other node, and at the end of the loading process, which node is passed back to the application as “loaded model” ?

There is nothing unique about osgTDS in the file loading.  it works like any other osg viewer in that all objects listed on the command line are grouped under a group node which is then formed as part of the main scene graph.  This is not unique to osgTDS.  The tds loader accepts a file named *.tds, then uses the information therein to find the other components, which need to preceed it on the command line.  It then divides the scene graph into "Terrain" and "Targets", manipulates the coordinates of the terrain according to the position of the targets.

3.       Is there any maximum or minimum distance up to which the terrain will be corrected to “touch” the target?

The software is designed to always connect to the target's "bottom", which is assumed to be coordinates of the "bottom hull", formed by the coords with lowest "z" value.  If you want to alter the behavior, you can insert targets that are used for manipulating the terrain, but not drawn.   

4.       Is it possible to use osgTDS for loading highdetail terrainmodels into larger low-detail, and osgTDS will adapt the low-level model that there is no z-fighting or things like that? Or is it better to use osgEarth for that purpose?

I have no idea what osgEarth is.  But yes, osgTDS does, in fact, adapt the lower level model to the new set of coordinates.  This allows you to shape the surface of the terrain to your liking. 

5.       Is it possible to use osgTDS in combination with osgEarth? Both projects seem to use a loader-plugin over osgDB.

Again, I have no idea what osgEarth is.  osgDB and "loader-plugin" however are not mutually exclusive.  osgDB is the framework by which osgTDS and other plugins work.

-don 

Thanks for your help,

Torben

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