Geode code example

#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();
	
	// 设置顶点
	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
	osg::ref_ptr<osg::Vec3Array>normal = new osg:: Vec3Array();
	normal->push_back(osg::Vec3(1.0f,1.0f,1.0f)^osg::Vec3(0.0f,0.0f,0.0f));
	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(vt.get());
    
    // 绘制四边形
    geometry->addPrimitiveSet(new osg::DrawArray(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::OM);
        // 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());
    }
    
    // 创建Billboard对象
    osg::ref_ptr<osg::Billboard> billboard1 = new osg::Billboard();
    
    // 设置旋转模式为绕视点
    billboard->setMode(osg::Billboard::POINT_ROT_EYE);
    // 添加Drawable，并设置其位置，默认位置为osg::Vec3(0.0f,0.0f,0.0f)
    billboard1->addDrawable(geometry.get(),osg::Vec3(5.0f,0.0f,0.0f));
    osg::ref_ptr<osg::Billboard> billboard2 = new osg::Billboard();
    // 设置旋转模式为绕轴转，因此还需要设置旋转轴
    billboard2->setMode(osg::Billboard::AXIAL_ROT);
    // 设置旋转轴
    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()
{
    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());
    
    // 获取cow的模型，以进行对比
    root->addChild(osgDB::readNodeFile("cow.osg"));
    
    // 优化场景数据
    osgUtil::Optimizer optimizer;
    optimizer.optimize(root.get());
    
    viewer->setSceneData(root.get());
    viewer->realize();
    viewer->run();
    
    return 0;    
}