Hi daniel, I read thru this at the osg site :
http://www.openscenegraph.org/projects/osg/wiki/Support/Maths/MatrixTransformations In the end , robert says ways are defined ... i initially multiplied the matrix on the left side. But after reading this i changed it...am i wrong ? Siddharth ----- Original Message ---- From: Daniel Holz <[EMAIL PROTECTED]> To: OpenSceneGraph Users <osg-users@lists.openscenegraph.org> Sent: Saturday, December 1, 2007 2:35:52 PM Subject: Re: [osg-users] Getting world coord bounding box hi, don't you have to multiply the matrix from the left side with the vector, like this: M * x = x', whereas M is your 'WorldCoordsMatrix', x is your local BBox vector and x' is the same in world coords. hope this helps. daniel Siddharth Palaniappan wrote: > Hi osg users, > > I'm currently using openscenegraph for my class project to simulate traffic. I have a problem in that , i need to find collision detection between consecutive cars and stop the car if there is a collision. I have followed the osgExample- for animation. I have used an animationpath and animationpathcallback and i have implemented my own spline interpolation for the car to traverse on a spline. I tried to get the world coordinate of the bounding box like this.. > > * i have a class Vehicle that stores the node to which an openflight model is read into. > > * the leaf node is the node having the vehicle, the parent node of this node is a transformation node which has an animationpathcallback set to, and this also has a parent node to initially set the location and orientation, (just like in the osgExample animation). > > * i have a node visitor that traverses parents..so it goes from the current node to the root concatenating all the world coordinates. > > * then i get the local bounding box of the node and get the minimum and maximum and multiply the world coord matrix with these points to form a new min and max point and create a new bounding box. I do this for every two node to check the intersection of two consecutive nodes. > > > //getWorldCoords() - forwards to a nodevisitor to get world coords matrix. > osg::Matrixd* WorldCoordsMatrix = getWorldCoords(this->m_Vehicle) ; > osg::BoundingBox VehicleBBox ; > > VehicleBBox.expandBy(m_Vehicle->getBound()) ; > > //Convert the vehicle local coords to world coordinates. > osg::Vec3f MinPt(VehicleBBox.xMin() , VehicleBBox.yMin() , VehicleBBox.zMin()) ; > osg::Vec3f MaxPt(VehicleBBox.xMax() , VehicleBBox.yMax() , VehicleBBox.zMax()) ; > > osg::Vec3f NewMinPt , NewMaxPt ; > NewMinPt = MinPt * (*WorldCoordsMatrix) ; > NewMaxPt = MaxPt * (*WorldCoordsMatrix) ; > > this->m_VehicleBoundingBox = new osg::BoundingBox(NewMinPt , NewMaxPt) ; > > I am not getting correct results. I get that the bounding boxes dont intersect at all or sometimes intersect at odd places. Please let me know if i'm doing something stupid or if i my understanding of anything wrong. > > > Thank you, > > Yours Sincerely, > > Siddharth > > > > > > > ____________________________________________________________________________________ > Never miss a thing. Make Yahoo your home page. > http://www.yahoo.com/r/hs > _______________________________________________ > osg-users mailing list > osg-users@lists.openscenegraph.org > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ____________________________________________________________________________________ Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
