[osg-users] vpb - libmini - opinion

Robert Osfield robert.osfield at gmail.com
Sun Sep 14 01:27:31 PDT 2008


Hi Cedric,

I'm not a CLOD expert, so I'd recommend asking some like Ben Discoe,
or others from the VirtualTerrainProject community, as VTP has plenty
of CLOD implementations to choose from so have lots of first hand
experience.

In terms of osgTerrain integration, the part you'd need to implement
would be a custom osgTerrain::TerrainTechnique that build/renders a
single TerrainTile according to the Elevation and Colour Layers
attached to it.

Right now VirtualPlanetBuilder assigns a GeometryTechnique to each
TerrainTile, but at runtime you can replace this with your own
technique via a Registry::ReadCallback that traverses loaded subgraphs
and does the replace.   Longer term, possible in the OSG-2.8 time
frame, my plan is to have the osgTerrain::Terrain node, that can be
used to decorate a subgraph containing TerrainTile, to provide the
default TerrainTechnique to use, this way you wouldn't need to have
the ReadCallback, you could just set the terrain technique on the
Terrain, and all its children would then use it.

Robert.

On Sat, Sep 13, 2008 at 4:55 PM, Cedric Pinson <mornifle at plopbyte.net> wrote:
> Hi Robert,
> I think to implement a clod technique for osg, i did not check all clod
> technique yet. My first candidate to evaluate is libmini. Would you have
> some advise about clod technique to use ? Ideally i would like to plug it to
> osgTerrain.
>
> Cheers,
> Cedric
>
> Cedric Pinson wrote:
>>
>> Thank you Robert for those informations.
>>
>> Cedric
>>
>> Robert Osfield wrote:
>>>
>>> Hi Cedric,
>>>
>>> VPB/osgTerrain doesn't yet have any blending between LOD levels so
>>> "popping" is still apparent.  The effect is less apparent now when
>>> using the --terrain option in VPB, as it creates tiles of higher
>>> resolution so the pixel errors associated with moving between LOD
>>> levels is lower.
>>>
>>> W.r.t libmini, the author of this library, Stefan Roettger,  was
>>> planning on writing an OSG NodeKit to interface the library with the
>>> OSG.  This was last year, but haven't had an update recently from
>>> Stephan so I don't know the status of this work.
>>>
>>> With the development of osgTerrain I designed it so we could implement
>>> new TerrainTechnique implementations, just now we just have a crude
>>> brute force GeometryTechnique implementation, but the path is
>>> available to integrate CLOD techniques as custom TerrainTechnique
>>> implementations, this would allow one to integrate external techniques
>>> but reuise the osgTerrain::TerrainTile data structure, so even in
>>> theory allow you to use VPB generated database with a tool like
>>> libmini.
>>>
>>> Robert.
>>>
>>> On Tue, Aug 19, 2008 at 8:11 PM, Cedric Pinson <mornifle at plopbyte.net>
>>> wrote:
>>>
>>>>
>>>> Hi all,
>>>>
>>>> Is there someone that has already try this library
>>>> (http://www.stereofx.org/terrain.html) in production ? On the example it
>>>> seems a little slow,  i would just want feedback compared to vpb osg.
>>>> Then i
>>>> have a second question, i did not try a recent version of vpb but i
>>>> remember
>>>> last time i used it there was some little popup when switching lod
>>>> level. Is
>>>> there something new to attenuate this effect ?
>>>> Then my last question, do you think that it would be useful to use new
>>>> algorithms that works with data in live like libmini ? I guess it
>>>> depends
>>>> the needed of the application, but i would like different opinions
>>>>
>>>> Cheers,
>>>> Cedric
>>>>
>>>> --
>>>> +33 (0) 6 63 20 03 56  Cedric Pinson mailto:mornifle at plopbyte.net
>>>> http://www.plopbyte.net
>>>>
>>>>
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>>>>
>>>
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>>
>
> --
> +33 (0) 6 63 20 03 56  Cedric Pinson mailto:mornifle at plopbyte.net
> http://www.plopbyte.net
>
>
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