[osg-users] Performance regression 3.6.3 vs 3.4.0

[Robert Osfield]

Hi Andrew

On Wed, 7 Aug 2019 at 23:43, Andrew Cunningham <osg-users at a-cunningham.com>
wrote:

> Firstly, has anyone noticed that http://forum.openscenegraph.org is
> basically off-line and has been malfunctioning for some time.
>

I think it was back working after a bit offline while I was away on
holiday, hadn't checked it recently (I don't admin the forum), checking
this morning it's offline again.

As a workaround for the above issue, and as I don't have any role in
management of the forum I took over admin of the osg-users googlegroups
mirror and enable it's use as a forum, though as the forum came backonline
I didn't announce it:

     https://groups.google.com/forum/#!forum/osg-users

So perhaps it's time to just default to the googlegroup.


> The link to the mailing list failed some time ago.
>
> In any case....
>
> I have noticed a serious performance regression when moving to 3.6.3 from
> 3.4.0
>
> It's  become such an issue for me, such that I had to revert to 3.4.0.
>
> The problem starts with Geometry::addPrimitiveSet
>
> .....

>
> I can eventually work around the issue, by doing my work to coalesce
> PrimitiveSets , but might be  a FYI for some users.
>

Just how many PrimitiveSet are you using?  It has to be pretty extreme to
cause performance issues when creating the scene.

My guess is that this slow down in creating the model is could be thought
of as a canary in the coal mine. OpenGL and modern hardware really don't
like being passed primitive data in small chunks, it's a huge performance
bottleneck having large number of small bottlenecks.

You will for sure get better performance when creating and rendering your
scene once you starting using a small number of primitive sets with a large
number of primitives.

Robert.
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