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<p class="MsoNormal">Hi all,<o:p></o:p></p>
<p class="MsoNormal">I have a performance issue in my scenegraph that I cannot completely understand.<o:p></o:p></p>
<p class="MsoNormal">My scenegraph is made by a main matrix transform, with these 2 children:<o:p></o:p></p>
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<li class="MsoListParagraph" style="margin-left:0cm;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="MsoListParagraph" style="margin-left:0cm;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">It seems that this configuration allows me to have at most 50 fps.<o:p></o:p></p>
<p class="MsoNormal">I feel that this should be rendered much faster.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">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">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">Any idea about what I can try to make rendering of my scenegraph faster?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks,<o:p></o:p></p>
<p class="MsoNormal">Gianluca<o:p></o:p></p>
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