I created a class intended to act as a floating label for components within
the scene. I would use the osg text library except that many of my labels
use sophisticated mathematical expressions which would be difficult to lay
out. What I do is generate my text using Mathematica, and then run it
through some code using Magick++ to clear the background. The code below is
what I am using to create the label in the scene.
When I use it, the labels appear with a white background. Using
osg::TexEnv::DECAL seems to let the color bound to the QUAD show through, but
what I really want is for the background part to be transparent so that the
rest of the scene shows through. Can that be accomplished? How?
class ComponentLabel : public osg::MatrixTransform {
//...
ComponentLabel( const std::string& fileName = "fileName_not_given")
this->setMatrix( osg::Matrix::translate( vec3f( from ) ) );
osg::AutoTransform * ax = new osg::AutoTransform();
ax->setAutoRotateMode( osg::AutoTransform::ROTATE_TO_CAMERA );
this->addChild( ax );
osg::Geode* g = new osg::Geode();
g->addDrawable( _edge_rptr.get() );
this->addChild( g );
ax->setPosition( vec3f( to ) );
osg::Geode * geode = new osg::Geode();
ax->addChild( geode );
osg::Geometry* geometry = new osg::Geometry();
geode->addDrawable( geometry );
osg::DrawElementsUInt* face = new osg::DrawElementsUInt(
osg::PrimitiveSet::QUADS, 0 );
geometry->addPrimitiveSet( face );
face->push_back( 0 );
face->push_back( 1 );
face->push_back( 2 );
face->push_back( 3 );
osg::Image * image = osgDB::readImageFile( fileName );
if ( !image ) {
std::cerr << "diagram::ComponentLabel(): failed to load file -> " <<
fileName << std::endl;
return ;
}
image->setFileName( fileName );
osg::Texture2D* texture = new osg::Texture2D();
texture->setImage( 0, image );
osg::Vec3Array* vertices = new osg::Vec3Array;
geometry->setVertexArray( vertices );
osg::Vec3 dw( image->s()/2, 0, 0 );
osg::Vec3 dh( 0, image->t()/2, 0 );
dw*=0.001f;
dh*=0.001f;
vertices->push_back( -( dw + dh ) );
vertices->push_back( dw - dh );
vertices->push_back( dw + dh );
vertices->push_back( -dw + dh );
osg::Vec2Array* texcoords = new osg::Vec2Array( 4 );
( *texcoords ) [ 0 ].set( 0.0f, 0.0f );
( *texcoords ) [ 1 ].set( 1.0f, 0.0f );
( *texcoords ) [ 2 ].set( 1.0f, 1.0f );
( *texcoords ) [ 3 ].set( 0.0f, 1.0f );
geometry->setTexCoordArray( 0, texcoords );
osg::StateSet* ss = geode->getOrCreateStateSet();
ss->setTextureAttributeAndModes( 0, texture, osg::StateAttribute::ON );
osg::TexEnv* texEnv = new osg::TexEnv();
texEnv->setMode( osg::TexEnv::REPLACE );
ss->setTextureAttribute( 0, texEnv );
geometry->setStateSet( ss );
osg::Vec4Array* color = new osg::Vec4Array;
color->push_back( osg::Vec4f( 0, 0, 0, 1 ) );
geometry->setColorArray( color );
geometry->setColorBinding( osg::Geometry::BIND_OVERALL );
}
};
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