Hi,
The LineSegmentIntersector creates NaN warnings when applied to a node with
zero scale. I've attached a 3 line change to osgintersection.cpp to reproduce
the issue.
The NaN's first pop up when OSG tries to invert a zero matrix here:
https://github.com/openscenegraph/osg/blob/master/src/osgUtil/LineSegmentIntersector.cpp#L294
Check with the following code snippet:
Code:
osg::Matrix zero(0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,1);
if (zero.invert(zero))
std::cout << "inverted " << zero << std::endl;
invert() returns true but the inverted matrix is
inverted {
-nan -nan -nan 0
-nan -nan -nan 0
-nan -nan -nan 0
nan nan nan 1
}
This looks like a bug in the Matrix invert function.
However even if the matrix was still zero instead of NaN, there is another
issue here:
osg::ref_ptr<LineSegmentIntersector> lsi = new
LineSegmentIntersector(_start * matrix, _end * matrix);
Multiplying a vec3 with a zero matrix will cause NaN's, because there is an 1.0
/ (mat * vec ...) in the Matrix::preMult(Vec3) function.
Not sure on the best way to fix this. Should we add explicit checks for zero
scaled matrices in the LineSegmentIntersector, or fix the Matrix and Vec
classes so they don't produce NaN's under any circumstances for (borderline)
valid input? The latter seems the cleaner fix but would have a performance
impact all over OSG.
Thank you!
Cheers,
Jannik
------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=65720#65720
/* OpenSceneGraph example, osgintersection.
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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*/
#include <osg/ArgumentParser>
#include <osg/ApplicationUsage>
#include <osg/Timer>
#include <osg/CoordinateSystemNode>
#include <osg/Notify>
#include <osg/io_utils>
#include <osg/PositionAttitudeTransform>
#include <osgDB/ReadFile>
#include <osgUtil/IntersectionVisitor>
#include <osgUtil/LineSegmentIntersector>
#include <osgSim/LineOfSight>
#include <osgSim/HeightAboveTerrain>
#include <osgSim/ElevationSlice>
#include <iostream>
struct MyReadCallback : public osgUtil::IntersectionVisitor::ReadCallback
{
#if 0
virtual osg::Node* readNodeFile(const std::string& filename)
{
return osgDB::readRefNodeFile(filename).release();
}
#endif
virtual osg::ref_ptr<osg::Node> readNodeFile(const std::string& filename)
{
return osgDB::readRefNodeFile(filename);
}
};
int main(int argc, char **argv)
{
// use an ArgumentParser object to manage the program arguments.
osg::ArgumentParser arguments(&argc,argv);
osg::ref_ptr<osg::Node> scene = osgDB::readRefNodeFiles(arguments);
if (!scene)
{
std::cout<<"No model loaded, please specify a valid model on the command line."<<std::endl;
return 0;
}
osg::ref_ptr<osg::PositionAttitudeTransform> transform (new osg::PositionAttitudeTransform);
transform->addChild(scene);
transform->setScale(osg::Vec3f(0,0,0));
transform->setCullingActive(false);
std::cout<<"Intersection "<<std::endl;
osg::BoundingSphere bs = scene->getBound();
scene = transform;
bool useIntersectorGroup = true;
bool useLineOfSight = true;
//osg::CoordinateSystemNode* csn = dynamic_cast<osg::CoordinateSystemNode*>(scene.get());
//osg::EllipsoidModel* em = csn ? csn->getEllipsoidModel() : 0;
if (useLineOfSight)
{
osg::Vec3d start = bs.center() + osg::Vec3d(0.0,bs.radius(),0.0);
osg::Vec3d end = bs.center() - osg::Vec3d(0.0, bs.radius(),0.0);
osg::Vec3d deltaRow( 0.0, 0.0, bs.radius()*0.01);
osg::Vec3d deltaColumn( bs.radius()*0.01, 0.0, 0.0);
osgSim::LineOfSight los;
#if 1
unsigned int numRows = 20;
unsigned int numColumns = 20;
osgSim::HeightAboveTerrain hat;
hat.setDatabaseCacheReadCallback(los.getDatabaseCacheReadCallback());
for(unsigned int r=0; r<numRows; ++r)
{
for(unsigned int c=0; c<numColumns; ++c)
{
osg::Vec3d s = start + deltaColumn * double(c) + deltaRow * double(r);
osg::Vec3d e = end + deltaColumn * double(c) + deltaRow * double(r);
los.addLOS(s,e);
hat.addPoint(s);
}
}
{
std::cout<<"Computing LineOfSight"<<std::endl;
osg::Timer_t startTick = osg::Timer::instance()->tick();
los.computeIntersections(scene.get());
osg::Timer_t endTick = osg::Timer::instance()->tick();
std::cout<<"Completed in "<<osg::Timer::instance()->delta_s(startTick,endTick)<<std::endl;
for(unsigned int i=0; i<los.getNumLOS(); i++)
{
const osgSim::LineOfSight::Intersections& intersections = los.getIntersections(i);
for(osgSim::LineOfSight::Intersections::const_iterator itr = intersections.begin();
itr != intersections.end();
++itr)
{
std::cout<<" point "<<*itr<<std::endl;
}
}
}
{
// now do a second traversal to test performance of cache.
osg::Timer_t startTick = osg::Timer::instance()->tick();
std::cout<<"Computing HeightAboveTerrain"<<std::endl;
hat.computeIntersections(scene.get());
osg::Timer_t endTick = osg::Timer::instance()->tick();
for(unsigned int i=0; i<hat.getNumPoints(); i++)
{
std::cout<<" point = "<<hat.getPoint(i)<<" hat = "<<hat.getHeightAboveTerrain(i)<<std::endl;
}
std::cout<<"Completed in "<<osg::Timer::instance()->delta_s(startTick,endTick)<<std::endl;
}
#endif
{
// now do a second traversal to test performance of cache.
osg::Timer_t startTick = osg::Timer::instance()->tick();
std::cout<<"Computing ElevationSlice"<<std::endl;
osgSim::ElevationSlice es;
es.setDatabaseCacheReadCallback(los.getDatabaseCacheReadCallback());
es.setStartPoint(bs.center()+osg::Vec3d(bs.radius(),0.0,0.0) );
es.setEndPoint(bs.center()+osg::Vec3d(0.0,0.0, bs.radius()) );
es.computeIntersections(scene.get());
osg::Timer_t endTick = osg::Timer::instance()->tick();
std::cout<<"Completed in "<<osg::Timer::instance()->delta_s(startTick,endTick)<<std::endl;
typedef osgSim::ElevationSlice::DistanceHeightList DistanceHeightList;
const DistanceHeightList& dhl = es.getDistanceHeightIntersections();
std::cout<<"Number of intersections ="<<dhl.size()<<std::endl;
for(DistanceHeightList::const_iterator dhitr = dhl.begin();
dhitr != dhl.end();
++dhitr)
{
std::cout.precision(10);
std::cout<<" "<<dhitr->first<<" "<<dhitr->second<<std::endl;
}
}
}
else if (useIntersectorGroup)
{
osg::Timer_t startTick = osg::Timer::instance()->tick();
osg::Vec3d start = bs.center() + osg::Vec3d(0.0,bs.radius(),0.0);
osg::Vec3d end = bs.center();// - osg::Vec3d(0.0, bs.radius(),0.0);
osg::Vec3d deltaRow( 0.0, 0.0, bs.radius()*0.01);
osg::Vec3d deltaColumn( bs.radius()*0.01, 0.0, 0.0);
unsigned int numRows = 20;
unsigned int numColumns = 20;
osg::ref_ptr<osgUtil::IntersectorGroup> intersectorGroup = new osgUtil::IntersectorGroup();
for(unsigned int r=0; r<numRows; ++r)
{
for(unsigned int c=0; c<numColumns; ++c)
{
osg::Vec3d s = start + deltaColumn * double(c) + deltaRow * double(r);
osg::Vec3d e = end + deltaColumn * double(c) + deltaRow * double(r);
osg::ref_ptr<osgUtil::LineSegmentIntersector> intersector = new osgUtil::LineSegmentIntersector(s, e);
intersectorGroup->addIntersector( intersector.get() );
}
}
osgUtil::IntersectionVisitor intersectVisitor( intersectorGroup.get(), new MyReadCallback );
scene->accept(intersectVisitor);
osg::Timer_t endTick = osg::Timer::instance()->tick();
std::cout<<"Completed in "<<osg::Timer::instance()->delta_s(startTick,endTick)<<std::endl;
if ( intersectorGroup->containsIntersections() )
{
std::cout<<"Found intersections "<<std::endl;
osgUtil::IntersectorGroup::Intersectors& intersectors = intersectorGroup->getIntersectors();
for(osgUtil::IntersectorGroup::Intersectors::iterator intersector_itr = intersectors.begin();
intersector_itr != intersectors.end();
++intersector_itr)
{
osgUtil::LineSegmentIntersector* lsi = dynamic_cast<osgUtil::LineSegmentIntersector*>(intersector_itr->get());
if (lsi)
{
osgUtil::LineSegmentIntersector::Intersections& intersections = lsi->getIntersections();
for(osgUtil::LineSegmentIntersector::Intersections::iterator itr = intersections.begin();
itr != intersections.end();
++itr)
{
const osgUtil::LineSegmentIntersector::Intersection& intersection = *itr;
std::cout<<" ratio "<<intersection.ratio<<std::endl;
std::cout<<" point "<<intersection.localIntersectionPoint<<std::endl;
std::cout<<" normal "<<intersection.localIntersectionNormal<<std::endl;
std::cout<<" indices "<<intersection.indexList.size()<<std::endl;
std::cout<<" primitiveIndex "<<intersection.primitiveIndex<<std::endl;
std::cout<<std::endl;
}
}
}
}
}
else
{
osg::Timer_t startTick = osg::Timer::instance()->tick();
#if 1
osg::Vec3d start = bs.center() + osg::Vec3d(0.0,bs.radius(),0.0);
osg::Vec3d end = bs.center() - osg::Vec3d(0.0, bs.radius(),0.0);
#else
osg::Vec3d start = bs.center() + osg::Vec3d(0.0,0.0, bs.radius());
osg::Vec3d end = bs.center() - osg::Vec3d(0.0, 0.0, bs.radius());
#endif
osg::ref_ptr<osgUtil::LineSegmentIntersector> intersector = new osgUtil::LineSegmentIntersector(start, end);
osgUtil::IntersectionVisitor intersectVisitor( intersector.get(), new MyReadCallback );
scene->accept(intersectVisitor);
osg::Timer_t endTick = osg::Timer::instance()->tick();
std::cout<<"Completed in "<<osg::Timer::instance()->delta_s(startTick,endTick)<<std::endl;
if ( intersector->containsIntersections() )
{
osgUtil::LineSegmentIntersector::Intersections& intersections = intersector->getIntersections();
for(osgUtil::LineSegmentIntersector::Intersections::iterator itr = intersections.begin();
itr != intersections.end();
++itr)
{
const osgUtil::LineSegmentIntersector::Intersection& intersection = *itr;
std::cout<<" ratio "<<intersection.ratio<<std::endl;
std::cout<<" point "<<intersection.localIntersectionPoint<<std::endl;
std::cout<<" normal "<<intersection.localIntersectionNormal<<std::endl;
std::cout<<" indices "<<intersection.indexList.size()<<std::endl;
std::cout<<" primitiveIndex "<<intersection.primitiveIndex<<std::endl;
std::cout<<std::endl;
}
}
}
return 0;
}
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