[osg-users] Slow down with shared nodes

Wed Mar 8 00:40:47 PST 2017

Hi Robert,

hopefully I am getting closer. I find out, that the source model might be
the problem. I exported an obj file from Bentley Microstation and imported
into OpenSceneGraph. When I now export the scene into an osg file, I see a
lot of PrimiteSets (e.g. > 1000). So I will end up with a lot calls to
DrawElementsUShort. When I load the obj file into 3dsmax convert it into a
fbx file and reexport it from OpenSceneGraph into an osg file, I have only
one PrimitiveSet with one DrawArrays call. This file is working well in
3.4.0 with sharing nodes.

So I guess there might be a problem with sharing osg::Geometry which has a
lot of primitive sets. In 3.2.3 it was working well. What do you think?

André

2017-03-08 8:59 GMT+01:00 Andre Normann <andre.normann at gmail.com>:

> Hi Robert,
>
> when I use display lists instead of vertex buffer objects (using osgUtil::GLObjectsVisitor),
> everything is fine with 3.4.0.
>
> André
>
>
> 2017-03-08 8:40 GMT+01:00 Andre Normann <andre.normann at gmail.com>:
>
>> Hi Robert,
>>
>> attached you will find two screenshots while running in
>> SingleThreaded-Mode. Using osgUtil::Optimizer does not make any big
>> difference. I will try to create an example, so that you can test it on
>> your computer.
>>
>> André
>>
>>
>> 2017-03-07 18:10 GMT+01:00 Robert Osfield <robert.osfield at gmail.com>:
>>
>>> Hi André,
>>>
>>> Thanks for the screenshots.  They tells us it's the draw dispatch that
>>> is gating performance, so the question now moves to why draw dispatch
>>> is so slow in this case.
>>>
>>> Are you running the osgUtil::Optimizer on your scene graph?
>>>
>>> Could you run the tests with SingleThreaded threading model?
>>>
>>> There may be chance that a bug fix to the OSG somewhere has tightened
>>> up the assumptions it makes about threading.  That's just a guess
>>> though, there still is too few titbits of information to know what the
>>> cause is.
>>>
>>> Robert.
>>>
>>>
>>>
>>> On 7 March 2017 at 16:40, Andre Normann <andre.normann at gmail.com> wrote:
>>> > Hi Robert,
>>> >
>>> > some more screenshots. This time without any other model.
>>> >
>>> > 3.2.3_1: My application using 3.2.3 and sharing nodes
>>> > 3.4.0_1: My application using 3.4.0 and sharing nodes
>>> > 3.4.0_2: My application using 3.4.0 without sharing nodes
>>> >
>>> > Best regards,
>>> > André
>>> >
>>> >
>>> > 2017-03-07 17:27 GMT+01:00 Andre Normann <andre.normann at gmail.com>:
>>> >>
>>> >> Hi Robert,
>>> >>
>>> >> I attached two screenshots. As you can see, I am doing nothing fancy
>>> here.
>>> >> There is a VirtualPlanetBuilder model present in the scene, but this
>>> model
>>> >> is hidden for my test case. The test scene contains only some thousand
>>> >> triangles and I am using a GeForce 1080 which can handle much more.
>>> >> Currently I have no idea what is going wrong here.
>>> >>
>>> >> -André
>>> >>
>>> >>
>>> >> 2017-03-07 11:33 GMT+01:00 Robert Osfield <robert.osfield at gmail.com>:
>>> >>>
>>> >>> Hi André,
>>> >>>
>>> >>> I can't think of any changes between 3.2.x and 3.4.0 that would cause
>>> >>> a slow down like you are describing.
>>> >>>
>>> >>> The best way to start looking at what might be the cause would be to
>>> >>> isolate what part of the application is the bottleneck, the first
>>> step
>>> >>> would be to use on the on screen stats and then look at the costs of
>>> >>> the update, event, cull, draw dispatch and draw GPU phases.
>>> >>>
>>> >>> Also have a look at the full stats with to see if there is a
>>> different
>>> >>> number of nodes or state being rendered in the two cases.
>>> >>>
>>> >>> Robert.
>>> >>>
>>> >>>
>>> >>>
>>> >>> On 7 March 2017 at 08:21, Andre Normann <andre.normann at gmail.com>
>>> wrote:
>>> >>> > Hi,
>>> >>> >
>>> >>> > I am currently migrating from OpenSceneGraph 3.2.3 to 3.4.0. In my
>>> >>> > application I get a significant slow down, when I share nodes.
>>> Here is
>>> >>> > a
>>> >>> > quick example layout of my scenegraph:
>>> >>> >
>>> >>> >
>>> >>> > Parent
>>> >>> >   |
>>> >>> >   + ---> MatrixTransform1 --> Node1
>>> >>> >   |
>>> >>> >   + ---> MatrixTransform2 --> Node1
>>> >>> >   |
>>> >>> >   ...
>>> >>> >   |
>>> >>> >   + ---> MatrixTransform3 --> Node1
>>> >>> >
>>> >>> > I have a root node with several MatrixTransforms. The nodes below
>>> the
>>> >>> > MatrixTransforms are shared. In 3.2.3 everything works well and I
>>> have
>>> >>> > a
>>> >>> > framerate of 60 Hz. In 3.4.0 the framerate drops with each new
>>> added
>>> >>> > MatrixTransform. But when I do not share the nodes and instead
>>> create
>>> >>> > clones
>>> >>> > with a DEEP_COPY_ALL flag, everything is well in 3.4.0.
>>> >>> >
>>> >>> > So what could cause the slow down in 3.4.0 with node sharing?
>>> >>> >
>>> >>> > I am using OpenSceneGraph 3.2.3/3.4.0 with a release build on
>>> Window 7.
>>> >>> >
>>> >>> >
>>> >>> > Best regards,
>>> >>> > André
>>> >>> >
>>> >>> >
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>>> >>
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>>> >
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>>
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