Re: [osg-users] If anyone knows please explain about GL_LIGHT0

[Thrall, Bryan]

YoungStone, Jeong wrote on 2012-06-27: 
 Hi,
 
 I'm studying OSG with Beginner's Guide Book.
 But I did not learn about OpenGL.
 
snip
 In the code, GL_LIGHT0 and GL_LIGHT1 is being used.
 
 I know there are from GL_LIGHT0 to GL_LIGHT7.
 
 In my opinion GL_LIGHT0 features seems to be different from others.
 
 Who can you explain GL_LIGHT0 is this?

I'm not sure what you're asking exactly but maybe this will help:

In OpenGL, there is nothing special about GL_LIGHT0.  However,
osgViewer::Viewer by default uses GL_LIGHT0 as a headlight. You can
change this behavior by setting the OSG_DEFAULT_LIGHTING environment
variable (see 'osgviewer --help-env') or by calling setLightingMode() on
your osgViewer::Viewer.

Hope this helps!
--
Bryan Thrall
Principal Software Engineer
FlightSafety International
bryan.thr...@flightsafety.com


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[osg-users] If anyone knows please explain about GL_LIGHT0

[YoungStone, Jeong]

Hi,

I'm studying OSG with Beginner's Guide Book.
But I did not learn about OpenGL.

First, let me show you the code related questions.


Code:
#include osg/MatrixTransform
#include osg/LightSource
#include osgDB/ReadFile
#include osgViewer/Viewer

osg::Node* createLightSource( unsigned int num, 
  const osg::Vec3 trans,
  const osg::Vec4 
color )
{
osg::ref_ptrosg::Light light = new osg::Light;
light-setLightNum( num );
light-setDiffuse( color );
light-setPosition( osg::Vec4( 0.0f, 0.0f, 0.0f, 1.0f ) );

osg::ref_ptrosg::LightSource lightSource = new osg::LightSource;
lightSource-setLight( light );

osg::ref_ptrosg::MatrixTransform sourceTrans = new 
osg::MatrixTransform;
sourceTrans-setMatrix( osg::Matrix::translate( trans ) );
sourceTrans-addChild( lightSource.get() );

return sourceTrans.release();
}



int main( int argc, char** argv )
{
osg::ref_ptrosg::Node model = osgDB::readNodeFile( cessna.osg );

osg::ref_ptrosg::Group root = new osg::Group;
root-addChild( model.get() );

osg::Node* light0 = createLightSource( 0, osg::Vec3( -20.0f,   0.0f, 
0.0f ), osg::Vec4( 1.0f, 1.0f, 0.0f, 1.0f ) );
osg::Node* light1 = createLightSource( 1, osg::Vec3(   0.0f, -20.0f, 
0.0f ), osg::Vec4( 0.0f, 1.0f, 1.0f, 1.0f ) );

root-getOrCreateStateSet()-setMode( GL_LIGHT0, 
osg::StateAttribute::ON );
root-getOrCreateStateSet()-setMode( GL_LIGHT1, 
osg::StateAttribute::ON );
root-addChild( light0 );
root-addChild( light1 );

osgViewer::Viewer viewer;
viewer.setSceneData( root.get() );

return viewer.run();
}



In the code, GL_LIGHT0 and GL_LIGHT1 is being used.

I know there are from GL_LIGHT0 to GL_LIGHT7.

In my opinion GL_LIGHT0 features seems to be different from others.

Who can you explain GL_LIGHT0 is this?

... 

Thank you!

Cheers,
YoungStone,

--
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=48576#48576





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