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
> >
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#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;
}
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