Hello all
@scraw : geometries doesn't have to share vertex arrays but bufferobjects..this
is not the same:
The pattern that maximize vao reutilization is the followed
Geom1
G1VertAttrib1->BO1 G1VertAttrib2->BO2...and a Unique IndexArray->BON
Geom2
G2VertAttrib1->BO1 G2VertAttrib2->BO2...and a Unique IndexArray->BON
With this pattern and vao sharing I have not only draw stage drop but also a
huge gpu charge decrease
The only problem is that you should use glDrawXXBaseVertex or offsetIndices of
your IndexArray
My bench in release this time
.............................................................. Cull Draw
GPU FPS
Pattern on all geometries with 1VAO/Geom 2 4 1.37
160
Pattern on all geometries with shared VAOs 2 2 0.47
200
So I think there's interest in sharing vaos
scrawl wrote:
> Hi,
>
> please correct me if I'm wrong (I have a naive understanding of VAO). I don't
> see the point of VAO sharing. If a VAO can be "shared" between two
> Geometries, that means the Geometries have the same set of vertex arrays,
> correct? So then why use two separate Geometries to begin with if they are
> identical? You can re-use a Geometry by attaching it to multiple parents.
>
> The only downside I could think of when re-using a Geometry is that a Node
> with more than one parent can cause problems (certain functions like
> getWorldMatrices() suddenly return multiple results). Or you might want to
> assign a different StateSet to each copy of the Geometry (but in that case
> you could decorate the Geometry with an intermediate node and set the
> StateSet there).
>
> I guess this might be a case where the pre-OSG3.4 way of having a Geometry
> attached to a Geode instead of directly into the scene graph makes more
> sense. That way doing Geometry sharing doesn't result in a multi-parented
> graph...
>
> Cheers,
> Jannik
------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=68394#68394
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