[osg-users] [Toward DrawElementBaseVertex as drawcall]

[Robert Osfield]

HI Julien,

Are you still talking about the same VAO implementation you original
proposed last year?

I tested this and decided against it.  In testing performance and
comparing it against my own non sharing VAO implementation the later
performance far better for a range of models that I have to test
against.  The biggest bag in performance between the two was on very
large models such as city models where there we are large number of
objects.  Even you unit test case performed better with my
implementation.  I found the CPU overhead in your implementations
swamped any other theoretical performance improvements.

The official VAO implementation that we now have is part of master,
performs well, looks to be pretty reliable.  As previously discussed
it may be possible to adapt this implementation to share the
osg::VertexArrayState object in cases where osg::Geometry share their
arrays.  However, such changes would have to justified by a real
performance improvement on real complete data.

Robert.

On 5 February 2017 at 23:34, Julien Valentin <julienvalentin51 at gmail.com> wrote:
> Hi all,
> Excuse me to return on an old debate but I can't achieve VAO sharing with the current design...I really need an easy way for drawing with basevertices
>
> To argue on the utility of VAO sharing among geometries, and (so on the replacement DrawElements to DrawElementBaseVertex as draw submission command):
>
> 1)GPU Pro 4 : Evaluating drawcall cpu overhead and GPU Draw Submission Limitations
> https://books.google.fr/books?id=_FnSBQAAQBAJ&pg=PA24&lpg=PA24&dq=cost+of+glbindvertexarray&source=bl&ots=1O1DTprEUD&sig=XBs_GMyYM8em72dF8fWnO3YeRKU&hl=fr&sa=X&ved=0ahUKEwiunsa8mMvOAhXDWRoKHXwuBN4Q6AEISzAE#v=onepage&q=cost%20of%20glbindvertexarray&f=true
> 2)Performances of my VAO proposal  have conforted me in facts vaos should be shared and draw calls should be submitted with basevertex.
> 1VAO/Geom  DrawCost 4
> shared VAOs  DrawCost 2
> (My VAO proposal contains a little overhead that can be easily deported to a NodeVisitor)
>
> I would like other sentiments on the subject
>
>
> Cheers
>
> ------------------
> Read this topic online here:
> http://forum.openscenegraph.org/viewtopic.php?p=70109#70109
>
>
>
>
>
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