Hi Peter,
Julien-Charles Levesque schrieb:
>
>> Hi,
>>
>> I'm trying to use a PolytopeIntersector in my scene and so far I have
>> succeeded but only by using the camera (i.e. mCamera->accept(PolyVisitor))
>> with a PolytopeIntersector built from x and y coordinates in window frame.
>> However I would rather pass the visitor the root of my scene. I am doing
>> this in a virtual reality project, and using the camera seems to complicate
>> things a fair bit because we modify projection matrices and viewports a
>> whole lot.
>> For my LineSegmentIntersector I have used 3D points in model space, which
>> worked fine when visiting the root of the scene. For the PolytopeIntersector
>> I am unsure how to do this... Only examples I have found so far used either
>> coordinates in projection space or coordinates in window space.
>>
>
> Yes, the examples do not use all available constructors of
> PolytopeIntersector.
> That is something that has been sitting on my to-do-list for a long time...
>
Here is my code... stripped down to a minimum. I assume that you have a 4x4
matrix containing orientation of your selector (lOrientation) and a vec3
containing it's position (lPosition). I built the polytope to point in the
direction of positive y-axis. Sorry for the french variable names and
comments here and there... I don't think they hurt readability much at this
level :P
However, I wasn't able to extract a reliable 3x3 rotation matrix from mouse
coordinates. I can only say that this code works well with the raw 3x3
orientation and position provided by my tracker. Do you have any idea for a
desktop variation ? I can implement it. I could also integrate all this in
the examplekeyboardmouse, once I've figured out how to do it with a mouse :P
osg::Vec3 lPosition;
osg::Matrixd lOrientation;
osg::Vec3d lEnd = lPosition + lOrientation * osg::Vec3d(0,LENGTH, 0);
//pointe vers Y à l'origine
//construction d'un polytope dans le repere monde.
osg::Polytope lPolytope;
osg::Plane lPlane;
osg::Vec3d lNorm;
//This is the angle by which your planes are rotated. Wider angle = larger
selection.
double lTheta = 0.5 * PI / 180.;
//Left X Plane
lNorm.set(cos(lTheta),sin(lTheta),0);
lNorm = lOrientation*lNorm;
lPlane.set(lNorm, lPosition);
lPolytope.add(lPlane);
//Right X Plane
lNorm.set(-cos(lTheta),sin(lTheta),0); //car cos(theta) = cos(-theta) et
sin(theta)=-sin(-theta)
lNorm = lOrientation*lNorm;
lPlane.set(lNorm, lPosition);
lPolytope.add(lPlane);
//Top Z Plane
lNorm.set(0,sin(lTheta),-cos(lTheta));
lNorm = lOrientation*lNorm;
lPlane.set(lNorm, lPosition);
lPolytope.add(lPlane);
//Bottom Z Plane
lNorm.set(0,sin(lTheta),cos(lTheta));
lNorm = lOrientation*lNorm;
lPlane.set(lNorm, lPosition);
lPolytope.add(lPlane);
//Far Y Plane.
lNorm.set(0,-1,0);
lNorm = lOrientation*lNorm;
lPlane.set(lNorm, lEnd);
lPolytope.add(lPlane);
osg::ref_ptr<osgUtil::PolytopeIntersector> lIntersecteur =
new osgUtil::PolytopeIntersector(lPolytope);
// Création d'un visiteur.
osg::ref_ptr<osgUtil::IntersectionVisitor> lVisiteur = new
osgUtil::IntersectionVisitor;
lVisiteur->setIntersector(lIntersecteur);
//Set mask only if you must... in our
//application it was for focusable objects.
//lVisiteur->setTraversalMask(OBJET_DESIGNABLE);
//Accept node at root of scene.
mRootNode->accept(lVisiteur);
if(lIntersecteur->containsIntersections())
{
// Récupère les objets en intersection avec la droite.
osgUtil::PolytopeIntersector::Intersections lIntersections =
lIntersecteur->getIntersections();
//Parcours la liste des intersections, en commençant par les objets les
plus près
for (osgUtil::PolytopeIntersector::Intersections::iterator lII =
lIntersections.begin();
lII != lIntersections.end();
lII++)
{
const osg::NodePath& lNodePath = lII->nodePath;
//Do whatever you have to here!
}
}
Cheers,
Julien-Charles
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