[osg-users] painting plane

Korolyov Ilia ya-breeze at ya.ru
Thu Sep 11 08:35:38 PDT 2008


Ok. Coming back to first letter - what is right way to do such painting?

As I understand, proper way to change scene - is using UpdateCallback.
But in UpdateCallback there is no camera information. So I can't define
suitable color for lines. In CullCallback there is camera information,
but it's forbidden to change scene in CullCallback.

It's possible to save reference to camera object in UpdateCallback
descendant. Is it correct way?

Thanks
Ilia


В Чтв, 11/09/2008 в 09:28 -0400, Tomlinson, Gordon пишет:
> Doubtful really as lines don't have back faces..
> 
> Gordon
> 
> __________________________________________________________
> Gordon Tomlinson
> Email  : gtomlinson @ overwatch.textron.com
> 
> 
> -----Original Message-----
> From: osg-users-bounces at lists.openscenegraph.org [mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of Korolyov Ilia
> Sent: Thursday, September 11, 2008 9:20 AM
> To: OpenSceneGraph Users
> Subject: Re: [osg-users] painting plane
> 
> Hello
> 
> This technic working fine for poligons, but is it possible to make this trick to lines? I need exactly two lines, not three as in triangle.
> 
> I trying in such way
> 
> group->addChild( geode_with_poligons );
> group->addChild( geode_with_lines );
> group->getOrCreateStateSet()->setMode( GL_CULL_FACE, GL_BACK |
> osg::StateAttribute::OVERRIDE | osg::StateAttribute::ON );
> 
> Thanks
> Ilia
> 
> В Чтв, 11/09/2008 в 14:46 +0400, Korolyov Ilia пишет:
> > Hello, Robert
> > 
> > Thanks so much - it really helps
> > 
> > Ilia
> > 
> > В Чтв, 11/09/2008 в 11:38 +0100, Robert Osfield пишет:
> > > Hi Ilia,
> > > 
> > > If one side of the plane should be red, and the other blue then you 
> > > could render two polygons for the plane, each with opposite winding 
> > > and colour, then use glCullFace(osg::CullFace) to cull the faces to 
> > > give the illusion of changing colour.  The other technique you could 
> > > use of two sided colour in the OpenGL lighting/material model, not 
> > > all hardware/drivers supports two side lighting though.
> > > 
> > > Robert.
> > > 
> > > On Thu, Sep 11, 2008 at 11:22 AM, Korolyov Ilia <ya-breeze at ya.ru> wrote:
> > > > Hello
> > > >
> > > > I need to draw a plane (more exactly two lines by three points). 
> > > > Problem is in plane color. It must depends on camera position 
> > > > relative plane side - red or blue.
> > > >
> > > > I did it with CullCallback, because it's only one way to get 
> > > > access to camera, which I can find.
> > > >
> > > > What is right way to do it?
> > > >
> > > > Thanks
> > > > Ilia
> > > >
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