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

[Christian Buchner]

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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