3第一个例子

#include <osgViewer/Viewer>


#include <osg/Node>
#include <osg/Geode>
#include <osg/Geometry>
#include <osg/Group>
#include <osg/Billboard>
#include <osg/Texture2D>
#include <osg/Image>
#include <osg/PositionAttitudeTransform>
#include <osg/MatrixTransform>


#include <osgDB/ReadFile>
#include <osgDB/WriteFile>


#include <osgUtil/Optimizer>


osg::ref_ptr<osg::Node> createBillboardTree(osg::ref_ptr<osg::Image> image)
{
//创建四边形
osg::ref_ptr<osg::Geometry> geometry = new osg::Geometry();


osg::ref_ptr<osg::Vec3Array> v = new osg::Vec3Array();
v->push_back(osg::Vec3(-0.5f, 0.0f, -0.5f));
v->push_back(osg::Vec3(0.5f, 0.0f, -0.5f));
v->push_back(osg::Vec3(0.5f, 0.0f, 0.5f));
v->push_back(osg::Vec3(-0.5f, 0.0f, 0.5f));

geometry->setVertexArray(v.get());


//设置法线数组
osg::ref_ptr<osg::Vec3Array> normal = new osg::Vec3Array();
normal->push_back(osg::Vec3(1.0f, 0.0f, 0.0f)^osg::Vec3(0.0f, 0.0f, 1.0f));

geometry->setNormalArray(normal.get());
geometry->setNormalBinding(osg::Geometry::BIND_OVERALL);


//设置纹理坐标
osg::ref_ptr<osg::Vec2Array> vt = new osg::Vec2Array();
vt->push_back(osg::Vec2(0.0f, 0.0f));
vt->push_back(osg::Vec2(1.0f, 0.0f));
vt->push_back(osg::Vec2(1.0f, 1.0f));
vt->push_back(osg::Vec2(0.0f, 1.0f));
geometry->setTexCoordArray(0, vt.get());


//绘制四边形
geometry->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::QUADS, 0, 4));


if (image.get())
{
//状态属性对象
osg::ref_ptr<osg::StateSet> stateset = new osg::StateSet();

//创建一个Texture2D属性对象
osg::ref_ptr<osg::Texture2D> texture = new osg::Texture2D();
//关联image
texture->setImage(image.get());
//关联Texture2D纹理对象，第三个参数默认为ON
stateset->setTextureAttributeAndModes(0, texture, osg::StateAttribute::ON);
//启用混合
stateset->setMode(GL_BLEND, osg::StateAttribute::ON);
//关闭光照
stateset->setMode(GL_LIGHTING, osg::StateAttribute::OFF);
geometry->setStateSet(stateset.get());
}




osg::ref_ptr<osg::Billboard> billboard1 = new osg::Billboard();
billboard1->setMode(osg::Billboard::POINT_ROT_EYE);
billboard1->addDrawable(geometry.get(), osg::Vec3(5.0f, 0.0f, 0.0f));


osg::ref_ptr<osg::Billboard>billboard2 = new osg::Billboard();
billboard2->setMode(osg::Billboard::AXIAL_ROT);
billboard2->setAxis(osg::Vec3(0.0f, 0.0f, 1.0f));
billboard2->addDrawable(geometry.get(), osg::Vec3(10.0f, 0.0f, 0.0f));


osg::ref_ptr<osg::Group> billboard = new osg::Group();
billboard->addChild(billboard1.get());
billboard->addChild(billboard2.get());


return billboard.get();
}


int main()
{
//创建Viewer对象，场景浏览器
osg::ref_ptr<osgViewer::Viewer> viewer = new osgViewer::Viewer();


osg::ref_ptr<osg::Group> root = new osg::Group();


//读取图像
osg::ref_ptr<osg::Image> image = osgDB::readImageFile("Images/tree0.rgba");



//缩放，达到合适的大小
osg::ref_ptr<osg::PositionAttitudeTransform> pat = new osg::PositionAttitudeTransform();
pat->setScale(osg::Vec3(5.0f, 5.0f, 5.0f));
pat->addChild(createBillboardTree(image.get()));


root->addChild(pat.get());
//添加到场景
root->addChild(osgDB::readNodeFile("cow.osg"));




//优化场景数据
osgUtil::Optimizer optimizer;
optimizer.optimize(root.get());


// set the scene to render
viewer->setSceneData(root.get());


viewer->realize();


viewer->run();


return 0;
}