Hi Christoph,
On 11/08/2011 03:28 AM, "Christoph Fünfzig" wrote:
> Hi all,
>
> please consider the following case:
> I want to store a terrain as a geometry node
> (Positions and Normals as VBOs).
> Now I want to change small parts
> inside the Positions and Normals arrays only..
>
> What change policy for VBOs is actually used?
> With the "changed" marking of arrays,
> would it make sense to subdivide the terrain (in a cluster)?
> Is it possible to change arrays without getting entries
> into the change list?
>
> Any comments are well appreciated!
This is a case that OpenSG doesn't handle most efficiently right now. No matter
how small the change, changes are only recorded on a Field level. Between
threads there is no cost associated with it, as only pointers are swapped, so
that's not a problem. But for cluster distribution small changes in large
arrays
can be a problem. We just haven't come across many situations where that
happens, most of the time the whole array is replaced. So with the current
system subdividing the terrain into smaller pieces would help with cluster data
transfer.
In theory you could extend the ChangeList to support partial transfers. The
problem is in how you detect them, how you combine multiple partial changes,
and
how you handle insertions/deletions in addition to just changes. It's a big can
of worms to get it right...
Hope it helps
Dirk
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