[osg-users] PrimitiveSets and performance

[Riccardo Corsi]

Hi Glenn and Robert,

thank you for your suggestion.

I have written a little stress test application to try different
PrimitiveSet sizes,
but so fat it's providing inconsistent results with respect to my previous
benchmark (and in line to what I expected).
I wasn't able to isolate a culprit so far, I'll let you know if I spot
something.

Ricky


On Fri, Dec 2, 2016 at 6:36 PM, Robert Osfield <robert.osfield at gmail.com>
wrote:

> Hi Riccardo,
>
> I'm a surprised you saw a significant change in performance, in
> particular for the worse, this suggest that the merging has some kind
> of error in it or the driver isn't handling the larger sized
> primitives efficiently for some reason.
>
> One thing of note is that both the draw dispatch and the draw GPU are
> around the same amount slower in the merged case, this suggest that
> the something in happening in the driver/GPU combination that is
> blocking the OpenGL FIFO and then in turn blocking the OSG draw
> dispatch that is putting data into the OpenGL FIFO.
>
> There isn't any way for us to pinpoint what this might be with the
> details given.
>
> Check for GL errors being printed to the console.  Also try writing a
> your scene graph out to a .osgt  before and after the merge so you can
> QA the merge by hand - do this for a subset of your whole scene graph
> as reviewing a really big dataset will be really heavy on an editor.
>
> Robert.
>
>
> On 2 December 2016 at 15:32, Riccardo Corsi <riccardo.corsi at kairos3d.it>
> wrote:
> > Hi all,
> >
> > I'm trying to find out the best geometries and primitive sets layout on a
> > model that I'm using as performance benchmark.
> >
> > The model is quite heavy in terms of vertices and polygons, and
> everything
> > is rendered at the moment with DrawArrays.
> >
> > In the attempt to reduce the draw calls, I've recombined the primitive
> sets
> > contained in every geometry into a single primitive set.
> > I expected draw/gpu time to improve, and I've found the exact opposite -
> > find attached the 2 screenshots with the stats (before and after
> primitives
> > merge).
> >
> > After merging the primitive sets I've also tried to force VBO usage
> instead
> > of display lists, which improve things slightly, but always far worse
> than
> > before merging.
> >
> > Can anyone comment on this result?
> >
> > Thank you,
> > Riccardo
> >
> >
> >
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