[osg-users] Fwd: Slow down with shared nodes

[Andre Normann]

Hi Robert,

thanks for your help. I think the problem is the obj loader. I have done a
quick review of the source code and the loader seems to create for each "f"
line an own primitive set. This can be optimized. I will try to fix this in
near future.

I can not understand the difference between 3.2.3 and 3.4.0 on my computer.
Maybe indeed a driver problem. For now I have a working solution.


2017-03-08 15:35 GMT+01:00 Christian Buchner <christian.buchner at gmail.com>:

> I've recently written some code to merge individual triangle strips
> by joining them using some degenerate (zero area) triangles.
>
> One issue that I've run into is that in wireframe mode this generated
> some very odd looking artifacts.
>
> Find the code here. It may need some adaptation for your use case.
> http://forum.openscenegraph.org/viewtopic.php?t=16412
>
> Christian
>
>
> 2017-03-08 15:32 GMT+01:00 Robert Osfield <robert.osfield at gmail.com>:
>
>> Hi Andre,
>>
>> Thanks for the file.  I've just tried it on my Kubuntu 16.04. NVidia
>> 760 with the OSG-3.4 branch and I see decent performance, the draw
>> dispatch is bit more expensive than I'd usually expect for a model of
>> this size but it's not widely expensive like you are seeing.
>>
>> The dataset itself looks like the large number of PrimitiveSets is
>> very high for the number of vertices in each osg::Geometry.  The use
>> of very short triangle strips rather than a single DrawElementsUShort
>> GL_TRIANGLES is the core of what is wrong with how the osg::Geometry
>> have been generated.
>>
>> The source of this issue may be down to the .obj or perhaps original
>> data being very poorly set up.
>>
>> Robert.
>>
>> On 8 March 2017 at 09:39, Andre Normann <andre.normann at gmail.com> wrote:
>> > Hi Robert,
>> >
>> > I used 3.2.3 to load the obj files and converted it into ive format. In
>> > 3.2.3 I load the ive file, build my scenegraph and I get 60 fps. When I
>> now
>> > load the same ive file into 3.4.0, build my scenegraph, I get the slow
>> down.
>> >
>> > - There must be something which is causing the slow down in
>> OpenSceneGraph
>> > - The obj loader is creating a lot of primitive sets, which is not
>> optimal.
>> > In near future I will try to fix that issue.
>> >
>> > I created a test file. Simply do an "osgviewer SlowDownTest.zip".
>> >
>> >
>> >
>> > 2017-03-08 9:45 GMT+01:00 Robert Osfield <robert.osfield at gmail.com>:
>> >>
>> >> Hi Andre,
>> >>
>> >> On 8 March 2017 at 08:40, Andre Normann <andre.normann at gmail.com>
>> wrote:
>> >> > 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?
>> >>
>> >> It sounds like data import path is the crucial part, perhaps changes
>> >> to the .obj plugin between 3.2.3 and 3.4.0 are what is causing the
>> >> difference.
>> >>
>> >> Doing an:
>> >>
>> >>     osgconv myfile.obj myfile.osgt
>> >>
>> >> In 3.2.3 and 3.4.0 will tell you the differences that the plugin and
>> >> any optimization passes are making.
>> >>
>> >> Is there any chance you could share an example of one of these .obj
>> >> files that is causing the performance problems?
>> >>
>> >> Robert.
>> >
>> >
>> >
>> >
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