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<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Hi Chris,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">first of all, thanks for helping.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Each of those 200 objects is simply the shape of an arrow (basically a cone and a cylinder), whose geometry takes no more than 100 vertices.<br>
The drawable that renders each arrow is a custom drawable that I derived from osg::drawable, where I’ve overridden the drawImplementation.<br>
Internally my drawable allocates a VBO for the geometry, and sends it directly to OpenGL for rendering in drawImplementation.<br>
My drawable provides a consistent bounding box that OSG uses to cull the drawable when outside of the viewing volume.<br>
Each drawable is inserted in a geode, that in its turn is attached to an autotransform matrix, because I need those shapes to be rendered at constant size on screen (70 pixels).<br>
So, it is OSG that during rendering traversal computes the scale factors of that autotransform, to keep the constant size.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Note that I’m not using shaders at the moment, but still the ffp.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">At the beginning I had thought that my drawImplementation was the bottleneck in redrawing, but even if I comment its code completely<br>
(making drawImplementation an empty function), still the redraw takes a considerable time.<br>
It looks like most of the time was taken to traverse the scenegraph, apply the transformation and culling the drawables.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">I’m still investigating, and trying to isolate the issue.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Gianluca<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><b>Da:</b> osg-users <osg-users-bounces@lists.openscenegraph.org>
<b>Per conto di </b>Chris Hanson<br>
<b>Inviato:</b> martedì 8 ottobre 2019 15:51<br>
<b>A:</b> OpenSceneGraph Users <osg-users@lists.openscenegraph.org><br>
<b>Oggetto:</b> Re: [osg-users] R: multiple matrix transfromations cause severe slowness in performance<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I believe most computations you could imagine doing could be performed in the vertex shader during draw rather than by the CPU during cull.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">To describe more we'd need a better idea of what those 200 objects are, how they behave, what they represent, and how auto transform is being used.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Tue, Oct 8, 2019 at 7:36 AM Gianluca Natale <<a href="mailto:natale@europe.altair.com">natale@europe.altair.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">As I said, I’d like to use auto-transformations for those 200 objects, so I need 200 transformations for sure, and those transformations are updated by OSG at rendering time.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">So, the transformation has to be computed by OSG out of my vertex shader. Am I wrong?
<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b>Da:</b> osg-users <<a href="mailto:osg-users-bounces@lists.openscenegraph.org" target="_blank">osg-users-bounces@lists.openscenegraph.org</a>>
<b>Per conto di </b>Chris Hanson<br>
<b>Inviato:</b> martedì 8 ottobre 2019 14:42<br>
<b>A:</b> OpenSceneGraph Users <<a href="mailto:osg-users@lists.openscenegraph.org" target="_blank">osg-users@lists.openscenegraph.org</a>><br>
<b>Oggetto:</b> Re: [osg-users] multiple matrix transfromations cause severe slowness in performance<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Can you find a way to perform the transform on each object in a vertex shader and not have a unique state have to be calculated for each of the 200 objects?<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">On Tue, Oct 8, 2019 at 6:20 AM Gianluca Natale <<a href="mailto:natale@europe.altair.com" target="_blank">natale@europe.altair.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Hi all,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">I have a performance issue in my scenegraph that I cannot completely understand.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">My scenegraph is made by a main matrix transform, with these 2 children:<o:p></o:p></p>
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<li class="gmail-m3624598838946311341gmail-m2700963786699460416msolistparagraph" style="mso-list:l0 level1 lfo1">
One geode that renders a big object on screen (the geometry in the drawable can take up to several thousands vertices);<o:p></o:p></li><li class="gmail-m3624598838946311341gmail-m2700963786699460416msolistparagraph" style="mso-list:l0 level1 lfo1">
One group node that in its turn has 200 children, each made by a matrix transform and a geode. The drawable in each of those geodes is very simple (no more than 100 vertices)<o:p></o:p></li></ul>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">It seems that this configuration allows me to have at most 50 fps.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">I feel that this should be rendered much faster.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">So I made some experiment. If I remove the 200 matrix transform attached to the group node I mentioned above,<br>
and directly apply the transformations to the vertices of the geometries in the 200 drawables of the small objects, performance improves a lot, till 100 fps.<br>
I investigatd a bit inside OSG code (I’m using OG ver.3.4.1), and apparently the only overhead due to the additional matrix transformations is a call to glLoadMatrix (I’m using the old ffp).<br>
How can you explain such an improvement?<br>
<br>
My real problem is that I would like to replace the 200 matrix transfromations with 200 auto-transform matrices, since I’d like those small objects to keep constant size on screen.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">But if I do that, I cannot remove the 200 transformations at all, and I’ll end up with a bad performance.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Any idea about what I can try to make rendering of my scenegraph faster?<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Thanks,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Gianluca<o:p></o:p></p>
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<p class="MsoNormal" align="center" style="text-align:center">Chris 'Xenon' Hanson, omo sanza lettere.
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