[osg-users] LineSegmentIntersector::intersect + performance

Volckaert, Guy (CA - MTS) Guy.Volckaert at meggitt.com
Tue Jun 26 11:05:52 PDT 2018


I recently upgraded to the OSG v3.6.1 and I noticed that the new LineSegmentIntersector has changed significantly compared to v3.4.0. As I was reviewing the changes, I noticed that the LineSegmentIntersector now allocates an instance of LineSegmentIntersectorUtils::Settings every time the IntersectionVisitor intercepts a drawable.

>From a purely efficiency standpoint, I was wondering if we could do better. Intersection were relatively slow in the past and now it seems that we made even slower. That being said, I'm pretty sure there's a valid reason for why it was done this way. Before I look at alternative solutions, I was wondering if anyone could share for reasons.

Below is a snip-it of the function:

void LineSegmentIntersector::intersect(osgUtil::IntersectionVisitor& iv, osg::Drawable* drawable,
                                       const osg::Vec3d& s, const osg::Vec3d& e)
    if (reachedLimit()) return;

    osg::ref_ptr<LineSegmentIntersectorUtils::Settings> settings = new LineSegmentIntersectorUtils::Settings; ////// <<<<<<<<<< HERE <<<<<<<<<<<<
    settings->_lineSegIntersector = this;
    settings->_iv = &iv;
    settings->_drawable = drawable;
    settings->_limitOneIntersection = (_intersectionLimit == LIMIT_ONE_PER_DRAWABLE || _intersectionLimit == LIMIT_ONE);

    osg::Geometry* geometry = drawable->asGeometry();
    if (geometry)
        settings->_vertices = dynamic_cast<osg::Vec3Array*>(geometry->getVertexArray());

    osg::KdTree* kdTree = iv.getUseKdTreeWhenAvailable() ? dynamic_cast<osg::KdTree*>(drawable->getShape()) : 0;

    if (getPrecisionHint()==USE_DOUBLE_CALCULATIONS)
        osg::TemplatePrimitiveFunctor<LineSegmentIntersectorUtils::IntersectFunctor<osg::Vec3d, double> > intersector;
        intersector.set(s,e, settings.get());

        if (kdTree) kdTree->intersect(intersector, kdTree->getNode(0));
        else drawable->accept(intersector);
        osg::TemplatePrimitiveFunctor<LineSegmentIntersectorUtils::IntersectFunctor<osg::Vec3f, float> > intersector;
        intersector.set(s,e, settings.get());

        if (kdTree) kdTree->intersect(intersector, kdTree->getNode(0));
        else drawable->accept(intersector);


Guy Volckaert, ing.
Snr Software Engineer

Meggitt Training Systems (Quebec) Inc.
Systèmes d'entraînement Meggitt (Québec) Inc.
6140 Henri Bourassa West
Montreal, Quebec, H4R 3A6

Tel: 1 (514) 339 9938 Ext 617
Fax: 1 (514) 339 2641
Cell: 1 (514) 928-5641
email: guy.volckaert at meggitt.com
url; www.meggitt.com
skype: guy.volckaert

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