I think I figured it out. It looks like even with culling turned off, nodes that are behind the "eye point" are culled. See osgUtil/CullVisitor.cpp line 645.
I now calculate the view matrix as follows. osg::Matrixd matrix = osg::Matrixd::translate( -center ); matrix.postMultRotate( osg::Quat( PI, osg::Vec3d( 1.0, 0.0, 0.0 ) ) ); matrix.postMultTranslate( osg::Vec3d( 0.0, 0.0, -0.5 ) ); Adding the last translation transform to push the nodes away from the "eye point" made the problem go away. Is this a bug? Frank On Thu, Nov 13, 2008 at 11:38:14AM -0500, [EMAIL PROTECTED] wrote: > Hi Robert, > > Thanks for the quick response. That was a good suggestion. However it > looks like that is not the problem. All of my nodes live on the z=0.0 > plane and my projection matrix is > > osg::Matrixd::ortho( -aspectRatio, aspectRatio, -1.0, 1.0, -1.0, 1.0 ) > > I have attached a small code sample that exhibits the problem. > > Frank > > On Thu, Nov 13, 2008 at 04:24:37PM +0000, Robert Osfield wrote: > > Hi Frank, > > > > My best guess is that your projection matrix isn't wide enough to > > encompass your scene and near/far clipping is clipping out the > > fragments. This may well look like culling, often users do mistake > > clipping with culling so chase up the wrong part of the pipeline. > > > > Robert. > > > > On Thu, Nov 13, 2008 at 4:18 PM, <[EMAIL PROTECTED]> wrote: > > > Greetings osg community, > > > > > > I'm have written a custom MatrixManipulator for a 2D scene and I am > > > experiencing a strange problem. As I pan and zoom around, some of the > > > nodes in the scene disappear abruptly as if they are being culled > > > inappropriately. However, disabling culling has no effect. > > > > > > The behavior is erratic and unpredictable which smells to me like I'm on > > > the border of a floating point inequality. I have discovered two ways > > > that seem to make the problem go away. > > > > > > One: > > > > > > One of the transformations I use to construct the view matrix is > > > > > > osg::Matrixd::rotate( osg::Quat( PI, osg::Vec3d( 1.0, 0.0, 0.0 ) ) ) > > > > > > If I replace that with > > > > > > osg::Matrixd::scale( osg::Vec3d( 1.0, -1.0, 1.0 ) ) > > > > > > the problem seems to go away. > > > > > > Two: > > > > > > All of the nodes in my seen that exhibit this problem have a 2D > > > bounding box. i.e. > > > > > > osg::BoundingBox const & bb = pGeode->getBoundingBox(); > > > assert( bb.zMax() - bb.zMin() < 1e-5 ); > > > > > > If I give the nodes some depth so that the above assert would fail, > > > the problem seems to go away. > > > > > > I suspect that these are not actual solutions. In any case, I would like > > > to understand what is happening under the covers. Any ideas? > > > > > > Frank > > > > > > _______________________________________________ > > > 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 > > #include <osg/Geode> > #include <osg/Geometry> > #include <osgViewer/Viewer> > > #include <iostream> > #include <cassert> > > osg::ref_ptr< osg::Node > CreateGraph() > { > osg::ref_ptr< osg::Geode > pGeode = new osg::Geode(); > osg::ref_ptr< osg::Geometry > pGeometry = new osg::Geometry(); > pGeode->addDrawable( pGeometry.get() ); > > // Vertices > osg::ref_ptr< osg::Vec3Array > pVerts = new osg::Vec3Array( 4 ); > (*pVerts)[ 0 ] = osg::Vec3( 0.0, 0.0, 0.0 ); > (*pVerts)[ 1 ] = osg::Vec3( 1.0, 0.0, 0.0 ); > (*pVerts)[ 2 ] = osg::Vec3( 1.0, 1.0, 0.0 ); > (*pVerts)[ 3 ] = osg::Vec3( 0.0, 1.0, 0.0 ); // dosen't work > //(*pVerts)[ 3 ] = osg::Vec3( 0.0, 1.0, 0.1 ); // works as expected > pGeometry->setVertexArray( pVerts.get() ); > > pGeometry->addPrimitiveSet( new osg::DrawArrays( osg::PrimitiveSet::QUADS, > 0, 4 ) ); > > osg::ref_ptr< osg::Vec4Array > pColors = new osg::Vec4Array( 4 ); > (*pColors)[ 0 ] = osg::Vec4( 1.0f, 1.0f, 1.0f, 1.0f ); > (*pColors)[ 1 ] = osg::Vec4( 1.0f, 0.0f, 0.0f, 1.0f ); > (*pColors)[ 2 ] = osg::Vec4( 0.0f, 1.0f, 0.0f, 1.0f ); > (*pColors)[ 3 ] = osg::Vec4( 0.0f, 0.0f, 1.0f, 1.0f ); > pGeometry->setColorArray( pColors.get() ); > pGeometry->setColorBinding( osg::Geometry::BIND_PER_VERTEX ); > > osg::ref_ptr< osg::StateSet > pState = pGeode->getOrCreateStateSet(); > pState->setMode( GL_LIGHTING, osg::StateAttribute::OFF ); > > osg::BoundingBox const & bb = pGeode->getBoundingBox(); > std::cout > << "BoundingBox = (" > << bb.xMin() << "," > << bb.yMin() << "," > << bb.zMin() << "," > << bb.xMax() << "," > << bb.yMax() << "," > << bb.zMax() << ")" > << std::endl; > > return pGeode.get(); > } > > int main( int argc, char * argv[] ) > { > int const x = 100; > int const y = 100; > int const w = 800; > int const h = 800; > > osg::ref_ptr< osg::GraphicsContext::Traits > pTraits = new > osg::GraphicsContext::Traits(); > pTraits->x = x; > pTraits->y = y; > pTraits->width = w; > pTraits->height = h; > pTraits->windowDecoration = true; > pTraits->doubleBuffer = true; > pTraits->sharedContext = 0; > > osg::ref_ptr< osg::GraphicsContext > pContext = > osg::GraphicsContext::createGraphicsContext( pTraits.get() ); > assert( pContext.valid() ); > > osgViewer::Viewer viewer; > > viewer.getCamera()->setGraphicsContext( pContext.get() ); > viewer.getCamera()->setClearColor( osg::Vec4( 0.0, 0.0, 0.0, 1.0 ) ); > viewer.getCamera()->setViewport( new osg::Viewport( 0, 0, w, h ) ); > viewer.getCamera()->setGraphicsContext( pContext.get() ); > viewer.getCamera()->setCullingMode( osg::CullSettings::NO_CULLING ); > > double const aspectRatio = double(w)/double(h); > //osg::Matrixd ortho = osg::Matrixd::ortho2D( -aspectRatio, aspectRatio, > -1.0, 1.0 ); > osg::Matrixd ortho = osg::Matrixd::ortho( -aspectRatio, aspectRatio, -1.0, > 1.0, -1.0, 1.0 ); > viewer.getCamera()->setProjectionMatrix( ortho ); > > osg::ref_ptr< osg::Node > pGraph = CreateGraph(); > > viewer.setSceneData( pGraph ); > > viewer.realize(); > > int n = 0; > int const N = 4000; // adjust for your computer speed > osg::Vec3d const initialCenter( 0.5, 0.5, 0.0 ); > > while ( !viewer.done() ) > { > n = ( n + 1 ) % N; > double d = -double(n)/double(N); > > osg::Vec3d center = initialCenter + osg::Vec3d( 0.0, d, 0.0 ); > //std::cout > // << "center = (" > // << center[0] << "," > // << center[1] << "," > // << center[2] << ")" > // << std::endl; > > osg::Matrixd matrix = osg::Matrixd::translate( -center ); > > // doesn't work > double const PI = 3.14159265; > matrix.postMultRotate( osg::Quat( PI, osg::Vec3d( 1.0, 0.0, 0.0 ) ) ); > > // works as expected, but left handed coordinate system is not desired > //matrix.postMultScale( osg::Vec3d( 1.0, -1.0, 1.0 ) ); > > viewer.getCamera()->setViewMatrix( matrix ); > > viewer.frame(); > } > > return 0; > } > > _______________________________________________ > 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
