一、程式碼

osg::ref_ptr<osg::Node> createSceneGraph()
{
	osg::ref_ptr<osg::Geometry> geom = new osg::Geometry();

	osg::ref_ptr<osg::Vec3Array> v = new osg::Vec3Array();
	geom->setVertexArray(v.get());
	//定義四個定點位置
	v->push_back(osg::Vec3(-1.f, 0.f, -1.f));
	v->push_back(osg::Vec3(1.f, 0.f, -1.f));
	v->push_back(osg::Vec3(1.f, 0.f, 1.f));
	v->push_back(osg::Vec3(-1.f, 0.f, 1.f));

	osg::ref_ptr<osg::Vec4Array> c = new osg::Vec4Array();
	geom->setColorArray(c.get());
	//設定顏色繫結模式
	geom->setColorBinding(osg::Geometry::BIND_PER_VERTEX);
	//設定顏色半透明， 注意顏色向量最後一位， 1.f表示完全不透明
	c->push_back(osg::Vec4(1.f, 0.f, 0.f, 0.2f));
	c->push_back(osg::Vec4(0.f, 1.f, 0.f, 0.2f));
	c->push_back(osg::Vec4(0.f, 0.f, 1.f, 0.2f));
	c->push_back(osg::Vec4(1.f, 1.f, 1.f, 0.2f));
	//設定法向量
	osg::ref_ptr<osg::Vec3Array> n = new osg::Vec3Array();
	geom->setNormalArray(n.get());
	geom->setNormalBinding(osg::Geometry::BIND_OVERALL);
	n->push_back(osg::Vec3(0.f, -1.f, 0.f));

	geom->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::QUADS, 0, 4));

	osg::ref_ptr<osg::Geode> geode = new osg::Geode();
	geode->addDrawable(geom.get());
	//開啟融合操作模式
	geode->getOrCreateStateSet()->setMode(GL_BLEND, osg::StateAttribute::ON);
	//設定渲染模式
	geode->getOrCreateStateSet()->setRenderingHint(osg::StateSet::TRANSPARENT_BIN);
	//關閉光照
	geode->getOrCreateStateSet()->setMode(GL_LIGHTING, osg::StateAttribute::OFF);

	return geode.get();
}
 

三、補充

當view更新後半透明效果失效， 查閱資料後得知是渲染級別的問題， 原來OSG載入進來的所有node渲染級別預設都是-1， 也就是說在未設定渲染級別的情況下， 渲染級別都是一樣的。在這種情況下，取消深度測試後以實現半透明效果，但半透明效果的node節點會被其它node節點“覆蓋， 所以需要如下操作： 

新增程式碼： geode->getOrCreateStateSet()->setRenderBinDetails(11, "RenderBin");

//Alpha blending on
geode->getOrCreateStateSet()->setMode(GL_BLEND, osg::StateAttribute::ON);       
geode->getOrCreateStateSet()->setRenderingHint(osg::StateSet::TRANSPARENT_BIN);
//Close the depth test
geode->getOrCreateStateSet()->setMode(GL_DEPTH_TEST, osg::StateAttribute::OFF); 
geode->getOrCreateStateSet()->setMode(GL_LIGHTING, osg::StateAttribute::OFF|osg::StateAttribute::PROTECTED);
//Set the rendering priority, if not set the default value is -1
geode->getOrCreateStateSet()->setRenderBinDetails(11, "RenderBin");