Thrall, Bryan wrote:
Paul Martz wrote on Thursday, May 28, 2009 4:50 PM:
You use a NodeVisitor to walk your scene graph and look for Geodes,
then iterate over the Drawables that are attached to the Geodes, using
dynamic_cast to access the Drawable as a Geometry.
Even better, I notice osg::Drawable has asGeometry(), which is cheaper
than dynamic_cast<> :)
Wow, I wasn't expecting the difference to be this large, as virtual
function calls aren't completely free either:
16:51|p...@tabu:~> cat t.cpp
// g++ -o t t.cpp -I ~/osg2.8/include/ -L ~/osg2.8/lib/ -losg -losgDB
#include <osgDB/ReadFile>
#include <sys/time.h>
float
timediff(struct timeval t0, struct timeval t1)
{
return 1000 * (t1.tv_sec - t0.tv_sec) + (t1.tv_usec - t0.tv_usec) /
1000.0;
}
int main()
{
osg::Group* cow = (osg::Group*)osgDB::readNodeFile("cow.osg");
osg::Geode* geode = (osg::Geode*)cow->getChild(0);
osg::Drawable *draw = geode->getDrawable(0);
bool isgeom = true;
int i;
struct timeval t0, t1, t2;
const int N = 100000;
gettimeofday(&t0, NULL);
for (i = 0; i < N; i++)
isgeom = isgeom && (draw->asGeometry() != NULL);
gettimeofday(&t1, NULL);
for (i = 0; i < N; i++)
isgeom = isgeom && (dynamic_cast<osg::Geometry*>(draw) != NULL);
gettimeofday(&t2, NULL);
printf("%d\n", isgeom); // need to use isgeom, as otherwise it
might be optimized away
printf("asGeometry() : %.3f ms\n", timediff(t0, t1));
printf("dynamic_cast<>(): %.3f ms\n", timediff(t1, t2));
}
16:52|p...@tabu:~> g++ -o t t.cpp -I ~/osg2.8/include/ -L ~/osg2.8/lib/
-losg -losgDB
16:52|p...@tabu:~> ./t
1
asGeometry() : 1.181 ms
dynamic_cast<>(): 3.945 ms
16:52|p...@tabu:~> g++ -O3 -o t t.cpp -I ~/osg2.8/include/ -L
~/osg2.8/lib/ -losg -losgDB
16:52|p...@tabu:~> ./t
1
asGeometry() : 0.839 ms
dynamic_cast<>(): 3.611 ms
16:52|p...@tabu:~>
Paul
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