Dont worry. *A lot of thanks for your reply*. Im interested in osgdem
code because Im really impressed by its outcomes. I had read that it is very
important to know how to distribute the nodes when you are working with
PagedLOD, so I thought that the best way to learn would be studying the VPB
code. Now Ive an idea.
Thanks again for your replay.
Robert Osfield <[EMAIL PROTECTED]> escribió: Hi Ignacio,
The osgdem app by default builds paged database, in fact this is
really what its all about, creating a single scene graph with LOD's
really is just a extra which comes effectively free from the
implementation, and is mainly just used for testing - for serious
usage one uses paged databases.
W.r.t paged databases, these are built top down as a quad tree, the
topmost file contains the lowest level of detail geometry and
textures, and also an external file reference for the next highest
level of detail. At runtime you don't need to know about all the high
res files, you just need to load the topmost file in the database and
the OSG will automatically do the paging in on demand for you. The
paging all takes its direction from the PagedLOD node, which are built
into the database.
Personally I'd recommend against trying to get to deep in working out
how VPB does its stuff internally. First up its complicated and I'm
waaay too over stretched to explain all the details. Second up, I'm
just starting a massive refactor of VPB so what you see now won't
necessarily apply to the future implementation.
If you want to know more about PagedLOD and paging please trawl
through the osg-users archives, there is lots of discussion over the
years.
Robert.
On 8/7/07, Ignacio José López Rodríguez wrote:
>
> Hi,
>
> I'm interested in knowing how is builded the scene graph by the "osgdem"
> program. To this end, last week I'd reading the "Virtual Planet Builder"
> code but I still have some doubts, specifically when the PAGED_LOD mode is
> used.
>
> On the one hand, I'm able to follow how is linked the scene graph when the
> simple LOD mode is set. If I'm not wrong it's instantiated a new LOD node
> which in turn is composed of both a geometry node and a group of descendants
> (if they are). Likewise its descendants are LODs node.
>
> However, when the PAGED_LOD mode is set I don't catch when nodes are linked
> among them. That is, after reading the code it gives me the impression that
> all nodes are written in the filesystem but I cannot see where they are
> linked adn so where the scenegraph is builded. Likely, there is something
> about the PAGED_LOD concept that I don't understand yet because I don't know
> either why the QuadMap is used for the PAGED_LOD nodes instead of the
> CompositeDestination graph.
>
> I'll appreciate any help.
>
> Thanks in advance,
>
>
>
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>
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> ¿Quieres saber cómo? ¡Deja que otras personas te ayuden! .
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