Hello everyone,
i spent my last weeks to find a reasonable cause concerning
osgUtil::LineSegmentIntersector on some osgt file.
In detail, i would like to identify objects in the scene, using line isector
(ray casting) starting from a certain point with a ray of 3 meter length .
Following the code i used for detecting object in front of camera (i'm using
osg 3.5.3 and Oculus Rift device)
Code:
osg::ref_ptr<osgUtil::LineSegmentIntersector> intersector = new
osgUtil::LineSegmentIntersector(startPoint, endPoint);
osgUtil::IntersectionVisitor iv(intersector.get());
//intersector->setIntersectionLimit(osgUtil::Intersector::LIMIT_NEAREST);
//intersector->setPrecisionHint(osgUtil::Intersector::PrecisionHint::USE_FLOAT_CALCULATIONS);
//for debugging: evaluation of visitor processing time
osg::Timer_t timer_tstart = mGlobalHighResTimer->tick();
iv.setTraversalMask(vrGame::INTERACTIVE);
subgraph->accept(iv);
//for debugging: evaluation of visitor processing time
osg::Timer_t timer_tend = mGlobalHighResTimer->tick();
double timer_tfinal = mGlobalHighResTimer->delta_m(timer_tstart, timer_tend);
std::cout << " Collision Visitor Time Computed : " <<
std::to_string(timer_tfinal) << std::endl;
This code works correctly in terms of dected object but some times i noticed
low performance when camera points in a space region near the object but not on
its geometry. I mean, if camera points the geometry of the object, performance
is ok. When camera points near the object (on an empty region) but not on its
geometry, performance drop down.
Some numbers: When camera points on empty area near the object, Oculus passes
from 90Hz to 45Hz framerate and the computation of
subgraph->accept(iv);
requires from 2.8 to 4 milliseconds for each frame.
I also investigated on osgUtil::IntersectionVisitor class, and it seems that
(in my specific situation),
IntersectionVisitor::apply(osg::Transform& transform)
needs from 2.8 to 4 ms computation time when processes the following code lines:
// now push an new intersector clone transform to the new local oordinates
push_clone();
traverse(transform);
// pop the clone.
pop_clone();
Another doubt is related to why, even if i set
iv.setTraversalMask(0x0001001)
for avoiding to process nodes which have that mask (and the investigated object
has this mask), visitor continues to process at each frame something that
requires a lot computation time.
The object comes from blender (osgt export), and has One group as root, a
MatrixTransform as child, a Geode as child and 3 drawables with 64K vertices on
the whole. The osgt file has 18 Mbytes size
My question is: Is there some solution I might adopt to improve these
performances? Can you give me some suggestions?
Thank you!
Cheers,
Andrea
------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=75275#75275
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