HI Wu, ClipNode has limitations because it controls position state - OpenGL state that has to be applied with a specific modelview matrix that gets encoded when that attribute is applied. This means that you can't just apply positional state at any time as it's value would be affected by rendering order/culling etc. The way the OSG avoids these issues is my applying positional state along with it's specific modelview matrix at the start of each RenderingStage and that particular state is then valid for the whole stage, but also you can't have multiple instances of that state applied otherwise you'd get clipplanes trying to be in multiple places at once. In the case of ClipNode it's the mechanism that allows the OSG to know which modelview matrix to use when applying the ClipPlane associated with it.
While this approach solves the issue of needing a reliable way to place positional state it does mean that you can only have one position in space for each positional state attribute per RenderingStage. My guess is that you are expecting ClipPlanes to work like non positional OpenGL state and can apply it multiple times by applying above different subgraphs, this however won't work one will take precidence. Robert. On 12 June 2014 11:25, ttaw <[email protected]> wrote: > Hi, everyone: > In my opinion, the clip effect of a clipnode only affects its child > nodes, and a new clipnode only uses its own clipplanes. But the fact seems > different from this. In the following project, a clipnode with a cow is > added to two parents, but only one cow is shown. How can I get two clipped > cows in result in the following code? > > > osg::Node* decorate_with_clip_node(osg::Node* node) > { > osg::Group* rootnode = new osg::Group; > osg::ClipNode* clipped_subgraph = new osg::ClipNode; > osg::BoundingSphere bs = node->getBound(); > bs.radius()*= 0.4f; > osg::BoundingBox bb; > bb.expandBy(bs); > clipped_subgraph->createClipBox(bb); > clipped_subgraph->addChild(node); > osg::MatrixTransform *mt1 = new osg::MatrixTransform; > mt1->addChild(clipped_subgraph); > osg::MatrixTransform *mt2 = new osg::MatrixTransform; > osg::Matrixd mat; > mat.makeTranslate(bs.radius()*2, bs.radius()*2, bs.radius()*2); > mt2->setMatrix(mat); > mt2->addChild(clipped_subgraph); > rootnode->addChild(mt1); > rootnode->addChild(mt2); > return rootnode; > } > > int main( int argc, char **argv ) > { > // use an ArgumentParser object to manage the program arguments. > // load the nodes from the commandline arguments. > osg::Node* loadedModel = osgDB::readNodeFile("cow.osgt"); > > if (!loadedModel) > { > osg::notify(osg::NOTICE)<<"Please specifiy a filename and the > command line"<<std::endl; > return 1; > } > > // decorate the scenegraph with a clip node. > osg::Node* rootnode = decorate_with_clip_node(loadedModel); > > // run optimization over the scene graph > osgUtil::Optimizer optimzer; > optimzer.optimize(rootnode); > > osgViewer::Viewer viewer; > > // set the scene to render > viewer.setSceneData(rootnode); > return viewer.run(); > } > > ------------------ > Failure is the mother of success. > Wu Zhicheng > > > _______________________________________________ > 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
