[osg-users] OpenSceneGraph/osgEarth vs VulkanSceneGraph/vsgpagedlod

Robert Osfield robert.osfield at gmail.com
Wed Mar 24 09:18:38 PDT 2021

Hi Jason,

On Wed, 24 Mar 2021 at 15:22, Jason Beverage <jasonbeverage at gmail.com>

> Very impressive Robert!  As you said, comparing osgEarth to your example
> isn't exactly apples to apples since the implementation under the hood is
> quite different but this is still great.

Thanks.  Indeed it's apples to oranges comparison so we shouldn't draw too
many conclusions.  I guess I could rewrite the vsgpagedlod example into an
OSG equivalent so all the settings are the same.  I'd actually be quite a
nice OSG examp[le.  My priority for the OSG is support so I'll have to
leave this to others.

> From what I've seen from your performance reporting, vsg is significantly
> faster than osg in most of your tests.  Do you have a feel for how much of
> that is just Vulkan being faster than OpenGL vs some of the other
> improvements you've made in design decisions of VSG vs OSG?  Are there any
> opportunities for porting some of the structures or concepts from VSG back
> to OSG to get some of the performance benefits you've seen in VSG in OSG?

The CPU overhead is much lower in the VSG than the OSG due to architecture
changes in the core Object/Node structure to reduce memory
footprint/bandwidth load and to avoid conditionals, These could be ported
into an OSG lite, but it'd break compatibility with a great many
applications - no BoundingSphere on all nodes, no NodeMask, no Callbacks,
no ancillary data stored in Object/Node.  It would break so many
applications and even the OSG itself it wouldn't be a small task to update

The differences are fundamental to the VSG delivering on the performance
capability that Vulkan provides, without it you'd only see a small %
improvement here or there if porting the OSG from OpenGL to Vulkan.  I've a
few applications and libraries that cite modest improvements when porting
to Vulkan, and don't recall any that claim 3 x to 10+ x faster than I'm
seeing on OSG vs VSG.  I think this either means the OSG is more of CPU hog
that we've long assumed or the VSG does a better job of not holding Vulkan
back by designing everything from the ground up to not get in the way as
much as possible.  I suspect it's a bit of both.


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