Hi, I have some doubts about my approach to create a GL3 non FFP context.
I have compiled osg with all the cmake settings for GL3 as explained in
lots of other posts.
When I create an object ( a simple two Vertex line ), usual camera
manipulation is working without me having writrten a single shader for
the vertex tranform. I expect this not to work, is this wrong ?
The geode is a child of a osg::PositionAttitudeTransform with a rotation
UpdateCallback. This also works, but it shouldn't without Shaders, right ?
Moreover, I create a StateSet for the Transform and give it
osg::StateSet::Callback to print all uniforms, no osg_ Uniforms ( e.g.
osg_ViewMatrix ) get printed out. Is it possible that all this works
without FFP ? I guess not.
How do I get these default osg_ Uniforms into the StateSet ? The only
place where I find code for creaating them is osgUtil::SceneView, which
is marked as deprecated.
As the glContextVersion of the GraphicsContext attached to the default
camera in the default viewer is 1.0, I use this way I set up the GL3
Context.
Please correct me if there is a better way, and if this does creat the
required context at all.
osg::GraphicsContext::Traits * traits = new
osg::GraphicsContext::Traits() ;
int width = 1920 , height = 1200 ;
traits -> x = 0 ;
traits -> y = 0 ;
traits -> width = width ;
traits -> height = height ;
traits -> windowDecoration = false ;
traits -> doubleBuffer = true ;
traits -> glContextVersion = std::string( "3.3" ) ;
osg::Camera * cam = new osg::Camera() ;
cam -> setGraphicsContext(
osg::GraphicsContext::createGraphicsContext( traits ) ) ;
cam -> setViewport( 0 , 0 , width , height ) ;
cam -> setClearMask( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ) ;
cam -> setClearColor( osg::Vec4( 0.0 , 0.0 , 0.0 , 1.0 ) ) ;
cam -> setProjectionMatrixAsPerspective( 30.0f , ( float )width / (
float )height , 1.0 , 1000.0 ) ;
viewer.setCamera( cam ) ;
// This Line::get() is defined bellow
viewer.setSceneData( Line::get() ) ;
This is the code for the callbacks and the Geometry, as mentined,
no Shaders attached, so why does Transformation work ?
class CBSS_Line : public osg::StateSet::Callback {
void operator()( osg::StateSet * stateSet , osg::NodeVisitor *
nodeVisitor ) {
const osg::StateSet::UniformList & uniformList = stateSet ->
getUniformList() ;
for( osg::StateSet::UniformList::const_iterator uitr =
uniformList.begin() ;
uitr != uniformList.end() ; ++uitr ) {
std::cout << uitr -> first << std::endl ;
}
}
} ;
class CBN_Line : public osg::NodeCallback {
void operator()( osg::Node * node , osg::NodeVisitor * nodeVisitor
) {
osg::PositionAttitudeTransform * xform = static_cast <
osg::PositionAttitudeTransform * >( node ) ;
xform -> setAttitude( osg::Quat( nodeVisitor -> getFrameStamp()
-> getSimulationTime() * osg::PI , osg::Z_AXIS ) ) ;
traverse( node , nodeVisitor ) ;
}
} ;
class Line {
public :
static osg::Node * get() {
osg::ref_ptr< osg::PositionAttitudeTransform > xformLine = new
osg::PositionAttitudeTransform() ;
xformLine -> addUpdateCallback( new CBN_Line ) ;
xformLine -> getOrCreateStateSet() -> setUpdateCallback( new
CBSS_Line ) ;
osg::ref_ptr< osg::Geode > geodeLine = new osg::Geode() ;
xformLine -> addChild( geodeLine.get() ) ;
osg::Geometry * geomLine = new osg::Geometry() ;
geodeLine -> addDrawable( geomLine ) ;
osg::Vec3Array * vrts = new osg::Vec3Array() ;
geomLine -> setVertexArray( vrts ) ;
osg::Vec4Array * rgba = new osg::Vec4Array() ;
geomLine -> setColorArray( rgba ) ;
geomLine -> setColorBinding( osg::Geometry::BIND_OVERALL ) ;
vrts -> push_back( osg::Vec3( 0.0f , 0.0f , 0.0f ) ) ;
vrts -> push_back( osg::Vec3( 1.0f , 0.0f , 0.0f ) ) ;
rgba -> push_back( osg::Vec4( 1.0f , 0.0f , 0.0f , 1.0f ) ) ;
geomLine -> addPrimitiveSet( new osg::DrawArrays(
osg::PrimitiveSet::LINES , 0 , 2 ) ) ;
osg::StateSet * stateSet = xformLine -> getOrCreateStateSet() ;
stateSet -> setAttributeAndModes( new osg::LineWidth( 5.0f ) ) ;
stateSet -> setMode( GL_LIGHTING , osg::StateAttribute::OFF ) ;
// Adding an Uniform to test the osg::StateSet::Callback
printing function
stateSet -> addUniform( new osg::Uniform( "Time" , 0.0f ) ) ;
// Not created this shader so far
//osg::Program * program = new osg::Program ;
//program -> addShader( osgDB::readShaderFile(
"shader/Line.vert" ) ) ;
//program -> addShader( osgDB::readShaderFile(
"shader/Line.frag" ) ) ;
//stateSet -> setAttributeAndModes( program ,
osg::StateAttribute::ON ) ;
return xformLine.release() ;
}
} ;
Thank you,
Cheers, PP
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