Hi, Conan gl_ModelViewMatrix * gl_Vertex is position of vertex in camera space If your view matrix dont have scale component, you dont need anything else to calculate distance (by distance i mean vector length) In general case you can use: osg_ViewMatrixInverse * gl_ModelViewMatrix * gl_Vertex <- this is world space vector from camera to vertex
Cheers, Sergey. 13.09.2011, 18:19, "Conan Doyle" <[email protected]>: > Hi, > > I want to calculate the distance between my final render cameras position and > the vertices of each object rendered. I want to pass the world position of > the camera into a shader and then use gl_Vertex position to perform the > calculation. In search the OSG website, the net and this forum (as I > understand a good OSG newbie should) I found the following > > http://www.openscenegraph.org/projects/osg/wiki/Support/Tutorials/CameraControlFindingWorldCoordinates > >> "Where in the world am I? >> To compute where a particular node is the scene graph is, in world >> coordinates, you need to acquire the accumulated 4x4 matrix from the root of >> the scene graph down to your node. osg::Node contains a convenience method, >> Node::getWorldMatrices(..), that walks the parental chain from your node to >> the root(s) of your scene graph, returning a list of matrices. A list of >> matrices is returned rather than a single matrix as the OpenSceneGraph >> supports sharing of nodes, so they may have multiple parents, and if the >> parent chain has separate transforms in them the different paths will result >> in different matrices - in this case you node is effectively in more than >> one place at once! Multiple parents would be typical in cases such as a >> wheel subgraph that is reused four times on a car, each with a transform >> above it to place it in the appropriate place. >> To use this feature use code such as: >> >> osg::MatrixList worldMatrices = myNode->getWorldMatrices(); >> >> for(osg::MatrixList::iterator itr = worldMatrices.begin(); >> itr != worldMatrices.end(); >> ++itr) >> { >> osg::Matrix& matrix = *itr; >> osg::Vec3 center = myNode->getBound().center() * matrix; >> std::cout<<"Node "<<myNode->getName()<<" center = "<<center<<" >> worldMatrix = "<<matrix<<std::end; >> } >> " > > I am wondering if this is what I need to do... with myNode being my viewer > camera node, and then getting the worldMatrix for it.... If so, how do I get > the position from the worldMatrix? > > Conan > > Thank you! > > Cheers, > Conan > > ------------------ > Read this topic online here: > http://forum.openscenegraph.org/viewtopic.php?p=42702#42702 > > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
